Gene regulators that are controlled by membrane-permeable compounds called homoserine lactones (HSLs) have become popular tools for building synthetic gene networks that coordinate behaviors across populations of engineered bacteria. Synthetic HSL-signaling systems are derived from natural DNA and protein elements from microbial quorum signaling pathways. Crosstalk, where a single HSL can activate multiple regulators, can lead to faults in networks composed of parallel signaling pathways. Here, we report an investigation of quorum sensing components to identify synthetic pathways that exhibit little to no crosstalk in liquid and solid cultures. In previous work, we characterized the response of a single regulator (LuxR) to 10 distinct HSL-synthase enzymes. Our current study determined the responses of five different regulators (LuxR, LasR, TraR, BjaR, and AubR) to the same set of synthases. We identified two sets of orthogonal synthase-regulator pairs (BjaI/BjaR + EsaI/TraR and LasI/LasR + EsaI/TraR) that show little to no crosstalk when they are expressed in Escherichia coli BL21. These results expand the toolbox of characterized components for engineering microbial communities.

In the present study we have used a quantitative immunoblotting method to measure the caldesmon content of a variety of smooth muscles with distinctly different contractile phenotypes. Two tonic vascular smooth muscles and several phasic smooth muscles were examined. The caldesmon, actin and myosin contents of each muscle type were measured. Smooth muscle from large arteries (i.e. bovine aorta and porcine carotid artery) had the lowest caldesmon content and phasic muscles (e.g. rat uterus and guinea pig taenia coli) had the highest. The molar ratio of monomeric caldesmon to monomeric actin was 1:205 for the aorta and carotid artery versus 1:22-28 for the taenia coli and uterus. The molar ratio of caldesmon to monomeric myosin heavy chain was 1:9 for the aorta and carotid versus 1:2 for the uterus and taenia coli. The caldesmon contents of canine trachealis and rabbit ileum were intermediate between these extremes. Evidence was found for the presence of both tissue- and species-specific caldesmon isoforms. The relatively high caldesmon content in rat uterus and guinea pig taenia coli suggests the possibility that the contractile phenotype associated with phasic smooth muscles may be dependent on the presence of caldesmon.

For mammals, acetylcholine (ACh) promotes endothelium-dependent vasodilation primarily through nitric oxide (NO) and prostaglandin-mediated pathways, with varying reliance on endothelial-derived hyperpolarizing factors. Currently, no studies have been conducted on small systemic arteries from wild birds. We hypothesized that ACh-mediated vasodilation of isolated small arteries from mourning doves (Zenaida macroura) would likewise depend on endothelial-derived factors. Small resistance mesenteric and cranial tibial (c. tibial) arteries (80-150 μm, inner diameter) were cannulated and pre-constricted to 50 % of resting inner diameter with phenylephrine then exposed to increasing concentrations of ACh (10(-9)-10(-5) M) or the NO donor, sodium nitroprusside (SNP; 10(-12)-10(-3) M). For mesenteric arteries, ACh-mediated vasodilation was significantly blunted with the potassium channel antagonist tetraethylammonium chloride (TEA, 10 mM); whereas responses were only moderately impaired with endothelial disruption or inhibition of prostaglandins (indomethacin, 10 μM). In contrast, endothelial disruption as well as exposure to TEA largely abolished vasodilatory responses to ACh in c. tibial arteries while no effect of prostaglandin inhibition was observed. For both vascular beds, responses to ACh were moderately dependent on the NO signaling pathway. Inhibition of NO synthase had no impact, despite complete reversal of phenylephrine-mediated tone with SNP, whereas inhibition of soluble guanylate cyclase (sGC) caused minor impairments. Endothelium-independent vasodilation also relied on potassium channels. In summary, ACh-mediated vasodilation of mesenteric and c. tibial arteries occurs through the activation of potassium channels to induce hyperpolarization with moderate reliance on sGC. Prostaglandins likewise play a small role in the vasodilatory response to ACh in mesenteric arteries.

Plasma glucose (PGlu) concentrations in birds are 1.5–2 times higher than those of mammals of similar body mass. In mammals, sustained elevations of PGlu lead to oxidative stress and free radical-mediated scavenging of endogenous vasodilators (e.g., nitric oxide), contributing to elevated blood pressure. Despite the relatively high PGlu levels in birds, they appear resistant to the development of oxidative stress in tissues such as the heart, brain and kidneys. To our knowledge no information exists on oxidative stress susceptibility in the resistance vasculature of birds. Therefore, we compared endogenous antioxidant mechanisms in the resistance vasculature of mourning doves (MODO; Zenaida macroura) and rats (Rattus norvegicus). Reactive oxygen species (ROS) were assessed with the fluorescent indicator 7′-dichlorodihydrofluorescein diacetate, acetyl ester in mesenteric arteries from rats and wild-caught MODO. Despite having significantly higher PGlu than rats, there were no significant differences in ROS levels between mesenteric arteries from rats or doves. Although superoxide dismutase and catalase activities were lower in the plasma, total antioxidant capacity, uric acid, vitamin E (α-tocopherol), and carotenoids (lutein and zeaxanthin) were significantly higher in MODO than in rats. Thus, compared to rats, MODO have multiple circulating antioxidants that may prevent the development of oxidative stress in the vasculature.

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