Research Triangle Park

About: Research Triangle Park is a nonprofit organization based out in Durham, North Carolina, United States. It is known for research contribution in the topics: Population & Environmental exposure. The organization has 24961 authors who have published 35800 publications receiving 1684504 citations. The organization is also known as: RTP.

Below‐ground carbon input to soil is controlled by nutrient availability and fine root dynamics in loblolly pine

Abstract: Summary • Availability of growth limiting resources may alter root dynamics in forest ecosystems, possibly affecting the land–atmosphere exchange of carbon. This was evaluated for a commercially important southern timber species by installing a factorial experiment of fertilization and irrigation treatments in an 8-yr-old loblolly pine (Pinus taeda) plantation. • After 3 yr of growth, production and turnover of fine, coarse and mycorrhizal root length was observed using minirhizotrons, and compared with stem growth and foliage development. • Fertilization increased net production of fine roots and mycorrhizal roots, but did not affect coarse roots. Fine roots had average lifespans of 166 d, coarse roots 294 d and mycorrhizal roots 507 d. Foliage growth rate peaked in late spring and declined over the remainder of the growing season, whereas fine roots experienced multiple growth flushes in the spring, summer and fall. • We conclude that increased nutrient availability might increase carbon input to soils through enhanced fine root turnover. However, this will depend on the extent to which mycorrhizal root formation is affected, as these mycorrhizal roots have much longer average lifespans than fine and coarse roots.

Trichomonas vaginalis Infection and Human Immunodeficiency Virus Acquisition in African Women

Abstract: Trichomoniasis vaginalis is the most common nonviral sexually transmitted infection (STI) worldwide with a particularly high prevalence in regions of human immunodeficiency virus (HIV) endemicity. However its impact as a cofactor for HIV acquisition is poorly understood. Samples from 213 women who experienced HIV seroconversion (cases) during a longitudinal study involving 4450 women in Uganda and Zimbabwe were matched with samples from HIV-uninfected women (controls). All samples underwent polymerase chain reaction (PCR) analysis for Trichomonas vaginalis DNA. For cases analyzed samples were from the visit in which HIV seroconversion was detected and the visit preceding detection of seroconversion; for controls one analyzed sample was from the visit matched by follow-up duration to the cases seroconversion visit and the other sample was from the visit immediately preceding the matched visit. The prevalence of T. vaginalis infection before HIV infection was 11.3% in cases and 4.5% in controls (P = .002). In multivariable analysis controlling for hormonal contraception other STIs behavioral and demographic factors the adjusted odds ratio for HIV acquisition was 2.74 (95% confidence interval 1.25-6.00) for T. vaginalis-positive cases. The presence of behavioral risk factors for HIV infection study recruitment from a referral population at high-risk for HIV primary sex partner-associated risk for HIV infection and herpes simplex virus type 2 seropositivity were also predictive of incident HIV infection. T. vaginalis infection is strongly associated with an increased risk for HIV infection in this general population of African women. Given the high prevalence of T. vaginalis infection in HIV-endemic areas T. vaginalis control may have a substantial impact on preventing HIV acquisition among women. (authors)

Acquired Resistance Signal Transduction in Arabidopsis Is Ethylene Independent.

Abstract: To clarify the role of ethylene in systemic acquired resistance (SAR), we conducted experiments using Arabidopsis ethylene response mutants. Plants that are nonresponsive to ethylene (i.e., [theta]tr1 and [theta]in2) showed normal sensitivity to the SAR-inducing chemicals salicylic acid (SA) and 2,6-dichloroisonicotinic acid with respect to SAR gene induction and pathogen resistance. This indicated that chemically induced SAR is not an ethylene-dependent process in Arabidopsis. Ethephon, an ethylene-releasing chemical, induced SAR gene expression in both the wild type and ethylene mutants, whereas ethylene alone did not, suggesting that induction of these genes by ethephon is not due to the action of ethylene. Furthermore, transgenic plants expressing salicylate hydroxylase, a bacterial enzyme that degrades SA to catechol, did not accumulate SAR mRNAs in response to ethephon. Thus, SAR gene induction by ethephon appears to be mediated through SA. Other experiments suggested that ethylene may play a role in SAR by enhancing tissue sensitivity to the action of SA.

Functional selectivity through protean and biased agonism: who steers the ship?

Abstract: This article describes functional selectivity of agonists and antagonists and distinguishes conventional cell-based functional selectivity, where the strength of signal produces selective signaling in various organs, from true receptor active-state based selectivity, also alternatively referred to in the literature as “stimulus trafficking,” “biased agonism,” and “collateral efficacy.” This latter mechanism of selectivity depends on the ligand-related conformation of the receptor and is not compatible with the parsimonious view that agonists produce a single receptor active state. In addition, protean agonism is described, whereby a ligand produces positive agonism in quiescent systems and inverse agonism in constitutively active systems. This is a special case of active state-based selectivity in which the ligand produces an active state that is of lower efficacy than the natural constitutively active state. It is postulated that receptor active-state based selectivity, unlike cell-based functional selectivity, is controllable through the chemical structure of the ligand and is therefore more likely to be a viable avenue for therapeutic selectivity in the clinic. Reasons are given for differentiating receptor active-state based selectivity from conventional functional organ selectivity.