5-hydroxytryptamine has an endothelium-derived hyperpolarizing factor-like effect on coronary flow in isolated rat hearts

Background

5-hydroxytryptamine (5-HT)-induced coronary artery responses have both vasoconstriction and vasorelaxation components. The vasoconstrictive effects of 5-HT have been well studied while the mechanism(s) of how 5-HT causes relaxation of coronary arteries has been less investigated. In isolated rat hearts, 5-HT-induced coronary flow increases are partially resistant to the nitric oxide synthase inhibitor Nω-Nitro-L-arginine methyl ester (L-NAME) and are blocked by 5-HT₇ receptor antagonists. In the present study, we investigated the role of 5-HT₇ receptor in 5-HT-induced coronary flow increases in isolated rat hearts in the absence of L-NAME, and we also evaluated the involvement of endothelium-derived hyperpolarizing factor (EDHF) in 5-HT-induced coronary flow increases in L-NAME-treated hearts with the inhibitors of arachidonic acid metabolism and the blockers of Ca²⁺-activated K⁺ channels.

Results

In isolated rat hearts, 5-HT and the 5-HT₇ receptor agonist 5-carboxamidotryptamine induced coronary flow increases, and both of these effects were blocked by the selective 5-HT₇ receptor antagonist SB269970; in SB269970-treated hearts, 5-HT induced coronary flow decreases, which effect was blocked by the 5-HT_2A receptor blocker {"type":"entrez-nucleotide","attrs":{"text":"R96544","term_id":"982204","term_text":"R96544"}}R96544. In L-NAME-treated hearts, 5-HT-induced coronary flow increases were blocked by the phospholipase A₂ inhibitor quinacrine and the cytochrome P450 inhibitor SKF525A, but were not inhibited by the cyclooxygenase inhibitor indomethacin. As to the effects of the Ca²⁺-activated K⁺ channel blockers, 5-HT-induced coronary flow increases in L-NAME-treated hearts were inhibited by TRAM-34 (intermediate-conductance Ca²⁺-activated K⁺ channel blocker) and UCL1684 (small-conductance Ca²⁺-activated K⁺ channel blocker), but effects of the large-conductance Ca²⁺-activated K⁺ channel blockers on 5-HT-induced coronary flow increases were various: penitrem A and paxilline did not significantly affect 5-HT-induced coronary flow responses while tetraethylammonium suppressed the coronary flow increases elicited by 5-HT.

Conclusion

In the present study, we found that 5-HT-induced coronary flow increases are mediated by the activation of 5-HT₇ receptor in rat hearts in the absence of L-NAME. Metabolites of cytochrome P450s, small-conductance Ca²⁺-activated K⁺ channel, and intermediate-conductance Ca²⁺-activated K⁺ channel are involved in 5-HT-induced coronary flow increases in L-NAME-treated hearts, which resemble the mechanisms of EDHF-induced vasorelaxation. The role of large-conductance Ca²⁺-activated K⁺ channel in 5-HT-induced coronary flow increases in L-NAME-treated hearts needs further investigation.     

Isolation and Genetic Characterization of Toxoplasma gondii from Black Bears (Ursus americanus), Bobcats (Lynx rufus), and Feral Cats (Felis catus) from Pennsylvania

Toxoplasma gondii infects virtually all warm‐blooded hosts worldwide. Recently, attention has been focused on the genetic diversity of the parasite to explain its pathogenicity in different hosts. It has been hypothesized that interaction between feral and domestic cycles of T. gondii may increase unusual genotypes in domestic cats and facilitate transmission of potentially more pathogenic genotypes to humans, domestic animals, and wildlife. In the present study, we tested black bear (Ursus americanus), bobcat (Lynx rufus), and feral cat (Felis catus) from the state of Pennsylvania for T. gondii infection. Antibodies to T. gondii were found in 32 (84.2%) of 38 bears, both bobcats, and 2 of 3 feral cats tested by the modified agglutination test (cut off titer 1:25). Hearts from seropositive animals were bioassayed in mice, and viable T. gondii was isolated from 3 of 32 bears, 2 of 2 bobcats, and 2 of 3 feral cats. DNA isolated from culture‐derived tachyzoites of these isolates was characterized using multilocus PCR‐RFLP markers. Three genotypes were revealed, including ToxoDB PCR‐RFLP genotype #1 or #3 (Type II, 1 isolate), #5 (Type 12, 3 isolates), and #216 (3 isolates), adding to the evidence of genetic diversity of T. gondii in wildlife in Pennsylvania. Pathogenicity of 3 T. gondii isolates (all #216, 1 from bear, and 2 from feral cat) was determined in outbred Swiss Webster mice; all three were virulent causing 100% mortality. Results indicated that highly mouse pathogenic strains of T. gondii are circulating in wildlife, and these strains may pose risk to infect human through consuming of game meat.     

Significance of hind wing morphology in distinguishing genera and species of cantharid beetles with a geometric morphometric analysis

There remain some difficulties in delimitation of related genera or sibling species for cantharid beetles, because the traditionally taxonomic method and morphological characters have not been updated or introduced. In the present study, we firstly use the landmark-based geometric morphometrics to analyze and compare the hind wings of nine species belonging to three genera of Cantharinae to ascertain whether this approach may be used as a reliable method in the study of the taxonomy of this group. The results show that the shape differences of the hind wings among genera seem more variable than that within each genus, and the variations for each species are different from one another, as shown in the principal component analyses. And the canonical variates analyses show that there are significant differences among the genera and the species of each genus, which demonstrates that the hind wing shape can be diagnostic for both generic and specific identification of the cantharid beetles. This study sheds new light into clarifying the taxonomic uncertainties of Cantharidae, and lays a foundation for further studies on the evolution of the cantharid hind wing shape.     

Existing joint erosions increase the risk of joint space narrowing independently of clinical synovitis in patients with early rheumatoid arthritis

IntroductionClinical synovitis is often associated with damage to bone and cartilage. Previous data have suggested that joint erosions (JE) are more prevalent than joint space narrowing (JSN) and that the two processes are partly independent of each other. The objective of this study was to evaluate whether the presence of JE in an individual joint can lead to development of JSN and if existing JSN leads to new onset of JE, in the absence of synovitis.MethodsThe Prospective Multi-Centre Randomised, Double-Blind, Active Comparator-Controlled, Parallel-Groups Study Comparing the Fully Human Monoclonal Anti-TNFα Antibody Adalimumab Given Every Second Week With Methotrexate Given Weekly and the Combination of Adalimumab and Methotrexate Administered Over 2 Years in Patients With Early Rheumatoid Arthritis (PREMIER) enrolled early rheumatoid arthritis (RA) patients who were randomized to one of three treatments: methotrexate (MTX), adalimumab (ADA), or ADA + MTX. All evaluable joints with JE and JSN measures at 26 and 52 weeks and synovitis assessments from week 26 to 52 were included. Synovitis was assessed every 2–8 weeks by swollen joint counts between weeks 26 and 52. Radiographs were taken at week 26 and 52. Two readers, blinded to time and sequence, scored 14 bilateral joints individually for JE and JSN. Multivariate logistic modeling was used to characterize the dependence of JE/JSN onset at 52 weeks. Analyses were performed based on treatment arm and were also performed within individual joints.ResultsJE and swelling were independently and comparably associated with onset of JSN at week 52. Assessment by individual joints indicated that existing JE, independent of swelling, was significantly associated with JSN onset in higher proportions of metatarsophalangeal (MTP; 7/10) than proximal interphalangeal (PIP; 1/8) or metacarpophalangeal (MCP; 1/10) joints. Treatment with ADA + MTX prevents JE/JSN progression independently of its ability to suppress synovitis and limits JE/JSN onset and progression in joints with existing damage.ConclusionsExisting JE predisposes individual joints to development of JSN independently of synovitis in the same joint. Weight-bearing MTP joints with JE may be at increased risk for JSN when compared with MCPs and PIPs.

Trial registration

Clinicaltrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00195663","term_id":"NCT00195663"}}NCT00195663. Registered 13 September 2005.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0626-1) contains supplementary material, which is available to authorized users.     

New strategy for in vitro activation of primordial follicles with mTOR and PI3K stimulators

It had been known for decades that primordial follicles in mammalian ovaries are assembled with definite numbers and represent the ovarian reserve throughout the reproductive life. Intra-oocyte PI3K/mTOR pathways have been indicated to play a central role on the activation of primordial follicles. Genetic modified mouse models with chronic activation of PI3K/mTOR signals in primordial oocytes showed premature activation of all primordial follicles and eventually their exhaustion. On the other hand, this may suggest that, unlike chronic activation of PI3K/mTOR, its acute activation in infertility would activate primordial follicles, permitting fertility during the treatment. Previously, PI3K stimulators were reported as a temporary measure to accelerate primordial follicle activation and follicular development in both mouse and human, and were applied in the treatment of infertility in premature ovarian failure (POF) patients. To address whether mTOR stimulators could play similar role in the process, we transiently treated neonatal and aged mouse ovaries with mTOR stimulators-phosphatidic acid (PA) and propranolol. Our results demonstrated the stimulators increased activation of primordial follicles and the production of progeny. Human ovarian cortex cubes were also treated with mTOR or/and PI3K stimulators in vitro. When they were used separately, both of them showed similar promotive effects on primordial follicles. Surprisingly, after joint-treatment with the 2 kinds of stimulators together, synergistic effects on follicular development were observed. Based on increased efficiency of follicular activation in humans, here we propose in vitro transient treatment with mTOR and PI3K stimulators as an optimized protocol for the application in different clinical conditions with limited follicle reserve.