Persistent alterations in heart rate variability, baroreflex sensitivity, and anxiety-like behaviors during development of heart failure in the rat

Depressed heart rate variability and mood are associated with increased mortality in patients with congestive heart failure (CHF). Here autonomic indexes were assessed 3 and 7 wk after left coronary artery ligation in telemetered rats, after which anxiety-like behaviors were assessed in an elevated plus maze. Low frequency (LF) and high frequency (HF) heart rate variability were reduced in CHF rats 3 wk after infarction (LF, 1.60 +/- 0.52 vs. 6.97 +/- 0.79 ms(2); and HF, 1.53 +/- 0.39 vs. 6.20 +/- 1.01 ms(2); P < 0.01). The number of sequences of interbeat intervals that correlated with arterial pressure was decreased in CHF rats at 3 and 7 wk (week 3, 26.60 +/- 10.85 vs. 59.75 +/- 11.4 sequences, P < 0.05; and week 7, 20.80 +/- 8.97 vs. 65.38 +/- 5.89 sequences, P < 0.01). Sequence gain was attenuated in CHF rats by 7 wk (1.34 +/- 0.06 vs. 2.70 +/- 0.29 ms/mmHg, P < 0.01). Coherence between interbeat interval and mean arterial blood pressure variability in the LF domain was reduced in CHF rats at 3 (0.12 +/- 0.03 vs. 0.26 +/- 0.05 k(2), P < 0.05) and 7 (0.16 +/- 0.02 vs. 0.31 +/- 0.05 k(2), P < 0.05) wk. CHF rats invariably entered the open arm of the elevated plus maze first and spent more time in the open arms (36.0 +/- 15% vs. 4.6 +/- 1.9%, P < 0.05). CHF rats also showed a tendency to jump head first off the apparatus, whereas controls did not. Together the data indicate that severe autonomic dysfunction is accompanied by escape-seeking behaviors in rats with verified CHF.     

8-[2-(4-Aryl-1-piperazinyl)ethyl]-2H-1,4-benzoxazin-3(4H)-ones: Dual-acting 5-HT1 receptor antagonists and serotonin reuptake inhibitors—Part II

8-[2-(4-Aryl-1-piperazinyl)ethyl]-2H-1,4-benzoxazin-3(4H)-ones have been identified as highly potent 5-HT_1A/B/D receptor antagonists with and without additional SerT activity and a high degree of selectivity over hERG potassium channels. Modulation of the different target activities gave compounds with a range of profiles suitable for further in vivo characterization.     

Identification of Naegleria fowleri in domestic water sources by nested PCR

The free-living amoeboflagellate Naegleria fowleri is the causative agent of primary amoebic meningoencephalitis (PAM), a rapidly fatal disease of the central nervous system. In the United States, the disease is generally acquired while swimming and diving in freshwater lakes and ponds. In addition to swimming, exposure to N. fowleri and the associated disease can occur by total submersion in bathwater or small backyard wading pools. In the present study, swipe samples and residual pipe water from homes in Arizona were examined for N. fowleri by nested PCR due to the death of two previously healthy children from PAM. Since neither child had a history of swimming in a freshwater lake or pond prior to the onset of disease symptoms, the domestic water supply was the suspected source of infection. Of 19 samples collected from bathroom and kitchen pipes and sink traps, 17 samples were positive for N. fowleri by PCR. A sample from a Micro-Wynd II filter was obtained by passing water from bathtubs through the filter. Organisms attached to the filter also tested positive by PCR. The two samples that tested negative for N. fowleri were one that was obtained from a kitchen sink trap and a swipe sample from the garbage disposal of one home.     

Population biology of the intertidal kelp, Alaria marginata Postels and Ruprecht: A non-fugitive annual

Persistence of annual plant populations requires sufficient seeds and suitable habitat for development and growth each year. Competition with perennials may prevent within site persistence and result in “fugitive” annual populations. Comparisons have been made between the population biology of annual macroalgae and terrestrial plants, but demographic information necessary to make strong comparisons is lacking for most of these algae, and life history differences may make such comparisons questionable. We studied population dynamics of the kelp Alaria marginata to determine if it was an annual and, if so, how populations persisted. This kelp is the dominant macroalga on exposed mid to low rocky intertidal shores along the Big Sur coast of California. Experimental clearings at two sites were used to assess recruitment timing and survivorship. Sporophytes were collected monthly to determine growth and fecundity. Recruitment occurred in late winter to early spring, primarily on geniculate corallines and residual A. marginata holdfasts. Thinning was inversely related to density, and occurred during the February through July growing season as larger thalli rapidly increased in length (up to 1.4 m month^− 1) and formed a thick canopy. Sorus development was positively related to size, began as early as March, peaked in late August-October, and decreased as adults were removed by winter surf. Spore release was generally highest (10⁸-10⁹ spores individual^− 11 h^− 1) between October and January and associated with high water motion. Survivorship of sporophytes beyond one year was < 1%, showing the populations were annual.Field observations and experiments on effects of canopy clearing, season of clearing, and influence of substrate type on recruitment were done to assess how these annual populations persist. Massive spore production at the onset of fall storms, survival of microscopic stages for 3-4 months facilitated by microhabitat refuges, rapid growth, large size and rapid maturation of sporophytes contributed to persistence. Furthermore, the dense stands with thick canopies may suppress potential competitors via shading and abrasion. Rather than being a fugitive, this combination of growth and life history features enables A. marginata and perhaps other large, annual kelps to maintain perennial populations.     

RNA-cleaving properties of human apurinic/apyrimidinic endonuclease 1 (APE1)

We have recently identified apurinic/apyrimidinic endonuclease 1 (APE1) as an endoribonuclease that cleaves c-myc mRNA in vitro and regulates c-myc mRNA levels and half-life in cells. This study was undertaken to further unravel the RNA-cleaving properties of APE1. Here, we show that APE1 cleaves RNA in the absence of divalent metal ions and, at 2 mM, Zn²⁺, Ni²⁺, Cu²⁺, or Co²⁺ inhibited the endoribonuclease activity of APE1. APE1 is able to cleave CD44 mRNA, microRNAs (miR-21, miR-10b), and three RNA components of SARS-corona virus (orf1b, orf3, spike) suggesting that, when challenged, it can cleave any RNAs in vitro. APE1 does not cleave strong doublestranded regions of RNA and it has a strong preference for 3’ of pyrimidine, especially towards UA, CA, and UG sites at single-stranded or weakly paired regions. It also cleaves RNA weakly at UC, CU, AC, and AU sites in single-stranded or weakly paired regions. Finally, we found that APE1 can reduce the ability of the Dicer enzyme to process premiRNAs in vitro. Overall, this study has revealed some previously unknown biochemical properties of APE1 which has implications for its role in vivo.     

Loopholes in the regulation of invasive species: genetic identifications identify mislabeling of prohibited aquarium plants

Numerous invasive aquatic species introductions can be traced to the aquarium trade. Many potentially harmful aquarium species may be difficult to identify based on morphology alone. As such, some prohibited or invasive species may be available for purchase if they are mislabeled as species without restrictions. Here we compare molecular identifications to internet vendors’ identifications for accessions of a popular genus of aquarium plants that are difficult to distinguish morphologically (Myriophyllum; watermilfoils). Specifically, we identified the extensive mislabeling of M. heterophyllum—an invasive species in the northeastern and western US. Furthermore, genotypes of M. heterophyllum found in our aquarium survey have also been found in invasive populations, suggesting their potential introduction through escape from aquaria, water gardens, or nurseries. Two additional taxa were sold under incorrect names. Finally, our survey revealed that Myriophyllum taxa present in the aquarium trade generally have poorly known distributions and ecologies, and therefore their invasive potential is unknown. Our study confirms that molecular identification methods can provide a valuable tool to survey commercial pathways for potentially harmful species that are otherwise difficult to identify.     

Substrate binding to Src: A new perspective on tyrosine kinase substrate recognition from NMR and molecular dynamics

Most signal transduction pathways in humans are regulated by protein kinases through phosphorylation of their protein substrates. Typical eukaryotic protein kinases are of two major types: those that phosphorylate‐specific sequences containing tyrosine (~90 kinases) and those that phosphorylate either serine or threonine (~395 kinases). The highly conserved catalytic domain of protein kinases comprises a smaller N lobe and a larger C lobe separated by a cleft region lined by the activation loop. Prior studies find that protein tyrosine kinases recognize peptide substrates by binding the polypeptide chain along the C‐lobe on one side of the activation loop, while serine/threonine kinases bind their substrates in the cleft and on the side of the activation loop opposite to that of the tyrosine kinases. Substrate binding structural studies have been limited to four families of the tyrosine kinase group, and did not include Src tyrosine kinases. We examined peptide‐substrate binding to Src using paramagnetic‐relaxation‐enhancement NMR combined with molecular dynamics simulations. The results suggest Src tyrosine kinase can bind substrate positioning residues C‐terminal to the phosphoacceptor residue in an orientation similar to serine/threonine kinases, and unlike other tyrosine kinases. Mutagenesis corroborates this new perspective on tyrosine kinase substrate recognition. Rather than an evolutionary split between tyrosine and serine/threonine kinases, a change in substrate recognition may have occurred within the TK group of the human kinome. Protein tyrosine kinases have long been therapeutic targets, but many marketed drugs have deleterious off‐target effects. More accurate knowledge of substrate interactions of tyrosine kinases has the potential for improving drug selectivity.