Tempo and mode of performance evolution across multiple independent origins of adhesive toe pads in lizards

Understanding macroevolutionary dynamics of trait evolution is an important endeavor in evolutionary biology. Ecological opportunity can liberate a trait as it diversifies through trait space, while genetic and selective constraints can limit diversification. While many studies have examined the dynamics of morphological traits, diverse morphological traits may yield the same or similar performance and as performance is often more proximately the target of selection, examining only morphology may give an incomplete understanding of evolutionary dynamics. Here, we ask whether convergent evolution of pad‐bearing lizards has followed similar evolutionary dynamics, or whether independent origins are accompanied by unique constraints and selective pressures over macroevolutionary time. We hypothesized that geckos and anoles each have unique evolutionary tempos and modes. Using performance data from 59 species, we modified Brownian motion (BM) and Ornstein–Uhlenbeck (OU) models to account for repeated origins estimated using Bayesian ancestral state reconstructions. We discovered that adhesive performance in geckos evolved in a fashion consistent with Brownian motion with a trend, whereas anoles evolved in bounded performance space consistent with more constrained evolution (an Ornstein–Uhlenbeck model). Our results suggest that convergent phenotypes can have quite distinctive evolutionary patterns, likely as a result of idiosyncratic constraints or ecological opportunities.     

Differential effect of ammonium on the induction of nitrate and nitrite reductase activities in roots of barley (Hordeum vulgare) seedlings

The effect of exogenous NH₄⁺ on the induction of nitrate reductase activity (NRA; EC 1.6.6.1) and nitrite reductase activity (NiRA; EC 1.7.7.1) in roots of 8-day-old intact barley (Hordeum vulgare L.) seedlings was studied. Enzyme activities were induced with 0.1, 1 or 10 mM NO₃⁺ in the presence of 0, 1 or 10 mM NH₄⁺, Exogenous NH₄⁺ partially inhibited the induction of NRA when roots were exposed to 0.1 mM, but not to 1 or 10 mM NO₃⁺, In contrast, the induction of NiRA was inhibited by NH₄⁺ at all NO₃⁺ levels. Maximum inhibition of the enzyme activities occurred at 1.0 mM NH₄⁺ Pre-treatment with NH₄⁺ had no effect on the subsequent induction of NRA in the absence of additional NH₄⁺ whereas the induction of NiRA in NH₄⁺-pretreated roots was inhibited in the absence of NH₄⁺ At 10 mM NO₃⁺ L-methionine sulfoximine stimulated the induction of NRA whether or not exogenous NH₄⁺ was present. In contrast, the induction of NiRA was inhibited by L-methionine sulfoximine irrespective of NH₄⁺ supply. During the postinduction phase, exogenous NH₄⁺ decreased NRA in roots supplied with 0.1 mM but not with 1mM NH₃⁺ whereas, NiRA was unaffected by NH₄⁺ at either substrate concentration. The results indicate that exogenous NH₄⁺ regulates the induction of NRA in roots by limiting the availability of NO₃⁺. Conversely, it has a direct effect, independent of the availability of NO₃⁺, on the induction of NiRA. The lack of an NH₄⁺ effect on NiRA during the postinduction phase is apparently due to a slower turnover rate of that enzyme.     

Development of PLEX, a plasmid-based expression system for production of heterologous gene products by the gram-positive bacteria Streptococcus gordonii

While Escherichia coli expression systems have been widely utilized for the production of heterologous proteins, these systems have limitations with regard to the production of particular protein products, including poor expression, expression of insoluble proteins into inclusion bodies, and/or expression of a truncated product. Using the surface protein expression (SPEX) system, chromosomally integrated heterologous genes are expressed and secreted into media by the naturally competent gram-positive organism Streptococcus gordonii. After E. coli turned out to be an inappropriate expression system to produce sufficient quantities of intact product, we successfully utilized SPEX to produce the heterologous antigen BH4XCRR that is designed from sequences homologous to the S. pyogenes M-protein C-repeat region. To further enhance production of this product by S. gordonii, we sought to develop a novel system for the production and secretion of heterologous proteins. We observed that under various growth conditions, S. gordonii secreted high levels of a 172 kDa protein, which was identified by N-terminal sequence analysis as the glucosyltransferase GTF. Here we report on the development of a plasmid-based expression system, designated as PLEX, which we used to enhance production of BH4XCRR by S. gordonii. A region from the S. gordonii chromosome that contains the positive regulatory gene rgg, putative gtfG promoter, and gtfG secretion-signal sequence was cloned into the E. coli/Streptococcus shuttle plasmid pVA838. Additionally, the bh4xcrr structural gene was cloned into the same plasmid downstream and in-frame with rgg and gtfG. This plasmid construct was transformed into S. gordonii and BH4XCRR was detected in culture supernatants from transformants at greater concentrations than in supernatants from a SPEX strain expressing the same product. BH4XCRR was easily purified from culture supernatant using a scalable two-step purification process involving hydrophobic-interaction and gel-filtration chromatography.     

Identification of vertebrate scavengers of small mammal carcasses in a forested landscape

We identified vertebrate scavengers of small mammal carcasses at the 780-km² Savannah River Site during the winter of 2000–2001. Rodent carcasses, differing in size and visual conspicuousness, were placed in upland pine forests and bottomland hardwood forests during six 2-week periods. Sixty-two of the 96 carcasses (65%) were removed by vertebrates. With the aid of remote photography, we identified 11 species of scavengers removing carcasses. RaccoonsProcyon lotor, gray foxesUrocyon cinereoargenteus, and feral pigsSus scrofa scavenged most frequently. The mean elapsed time for carcass removal was 5.6 days. The number of carcasses removed by vertebrates did not differ significantly with respect to carcass size, visual conspicuousness, or habitat type; however, air temperature was strongly correlated (positively) with carcass removal. Our study demonstrates that many mammal species are capable of utilizing small carrion items as a food resource, and suggests that scavenging may account for a higher proportion of the diet of some facultative scavengers than is now widely assumed.     

The cochlea of the enigmatic pygmy right whale Caperea marginata informs mysticete phylogeny

The pygmy right whale, Caperea marginata , is the least understood extant baleen whale (Cetacea, Mysticeti). Knowledge on its basic anatomy, ecology, and fossil record is limited, even though its singular position outside both balaenids (right whales) and balaenopteroids (rorquals + grey whales) gives Caperea a pivotal role in mysticete evolution. Recent investigations of the cetacean cochlea have provided new insights into sensory capabilities and phylogeny. Here, we extend this advance to Caperea by describing, for the first time, the inner ear of this enigmatic species. The cochlea is large and appears to be sensitive to low‐frequency sounds, but its hearing limit is relatively high. The presence of a well‐developed tympanal recess links Caperea with cetotheriids and balaenopteroids, rather than balaenids, contrary to the traditional morphological view of a close Caperea‐balaenid relationship. Nevertheless, a broader sample of the cetotheriid Herpetocetus demonstrates that the presence of a tympanal recess can be variable at the specific and possibly even the intraspecific level.     

Ospemifene inhibits the growth of dimethylbenzanthracene-induced mammary tumors in Sencar mice

Ospemifene is a new selective estrogen receptor modulator (SERM) that is being developed for the treatment of urogenital atrophy and osteoporosis. Similarly to other SERMs, ospemifene exhibits antiestrogenic effects in breast tissue, which led to the hypothesis that it may be a potential breast cancer chemopreventive agent. We first assessed the ability of ospemifene, compared to tamoxifen and raloxifene, to prevent dimethylbenzanthracene (DMBA)-induced mammary tumors in female Sencar mice. Ospemifene (N = 18), tamoxifen (N = 20) and raloxifene (N = 17), each dosed at 50 mg/kg, were administered daily by oral gavage, in combination with 20 microg DMBA for the first 6 weeks. Control mice (N = 21) received vehicle plus DMBA only for the first 6 weeks. Daily treatment then continued for 37 weeks. As hypothesized, ospemifene greatly reduced the incidence of mammary carcinomas compared to control mice (p = 0.003), similar to tamoxifen (p = 0.0004); however, in the raloxifene group, no significant effect was seen in mammary tumor prevention (p = 0.20). A follow-up study comparing ospemifene (N = 20) to tamoxifen (N = 20) in the same model was then performed to confirm the results of the first study. The results of the follow-up study, which extended the treatment to 52 weeks, confirmed the results of our previous study, with ospemifene (p = 0.01) and tamoxifen (p = 0.004) significantly decreasing mammary carcinomas compared to controls. The results of these two studies suggest that women taking ospemifene for osteoporosis and/or urogenital atrophy may further benefit from ospemifene's breast cancer chemopreventive effects.     

Characterization of the binding activities of proteinase-adhesin complexes from Porphyromonas gingivalis.

Adhesins from oral bacteria perform an important function in colonizing target tissues within the dentogingival cavity. In Porphyromonas gingivalis certain of these adhesion proteins exist as a complex with either of two major proteinases referred to as gingipain R (arginine-specific gingipain) and gingipain K (lysine-specific gingipain) (R. N. Pike, W. T. McGraw, J. Potempa, and J. Travis, J. Biol. Chem. 269:406-411, 1994). With specific proteinase inhibitors, it was shown that hemagglutination by either proteinase-adhesin complex could occur independently of proteinase activity. Significantly, low concentrations of fibrinogen, fibronectin, and laminin inhibited hemagglutination, indicating that adherence to these proteins and not the hemagglutination activity was a primary property of the adhesin activity component of complexes. Binding studies with gingipain K and gingipain R suggest that interaction with fibrinogen is a major function of the adhesin domain, with dissociation constants for binding to fibrinogen being 4 and 8.5 nM, respectively. Specific association with fibronectin and laminin was also found. All bound proteins were degraded by the functional proteinase domain, with gingipain R being more active on laminin and fibronectin and gingipain K being more effective in the digestion of fibrinogen. Cumulatively, these data suggest that gingipain R and gingipain K, acting as proteinase-adhesin complexes, progressively attach to, degrade, and detach from target proteins. Since such complexes appear to be present on the surfaces of both vesicles and membranes of P. gingivalis, they may play an important role in the attachment of this bacterium to host cell surfaces.     

Reduction of Brain Mitochondrial β-Oxidation Impairs Complex I and V in Chronic Alcohol Intake: The Underlying Mechanism for Neurodegeneration

Neuropathy and neurocognitive deficits are common among chronic alcohol users, which are believed to be associated with mitochondrial dysfunction in the brain. The specific type of brain mitochondrial respiratory chain complexes (mRCC) that are adversely affected by alcohol abuse has not been studied. Thus, we examined the alterations of mRCC in freshly isolated mitochondria from mice brain that were pair-fed the ethanol (4% v/v) and control liquid diets for 7–8 weeks. We observed that alcohol intake severely reduced the levels of complex I and V. A reduction in complex I was associated with a decrease in carnitine palmitoyltransferase 1 (cPT1) and cPT2 levels. The mitochondrial outer (cPT1) and inner (cPT2) membrane transporter enzymes are specialized in acylation of fatty acid from outer to inner membrane of mitochondria for ATP production. Thus, our results showed that alterations of cPT1 and cPT2 paralleled a decrease β-oxidation of palmitate and ATP production, suggesting that impairment of substrate entry step (complex I function) can cause a negative impact on ATP production (complex V function). Disruption of cPT1/cPT2 was accompanied by an increase in cytochrome C leakage, while reduction of complex I and V paralleled a decrease in depolarization of mitochondrial membrane potential (ΔΨ, monitored by JC-1 fluorescence) and ATP production in alcohol intake. We noted that acetyl-L-carnitine (ALC, a cofactor of cPT1 and cPT2) prevented the adverse effects of alcohol while coenzyme Q10 (CoQ10) was not very effective against alcohol insults. These results suggest that understanding the molecular, biochemical, and signaling mechanisms of the CNS mitochondrial β-oxidation such as ALC can mitigate alcohol related neurological disorders.