Conspecific plant–soil feedback scales with population size in Lobelia siphilitica (Lobeliaceae)

Plant–soil interactions directly affect plant success in terms of establishment, survival, growth and reproduction. Negative plant–soil feedback on such traits may therefore reduce the density and abundance of plants of a given species at a given site. Furthermore, if conspecific feedback varies among population sites, it could help explain geographic variation in plant population size. We tested for among-site variation in conspecific plant–soil feedback in a greenhouse experiment using seeds and soils from 8 natural populations of Lobelia siphilitica hosting 30–330 plants. The first cohort of seeds was grown on soil collected from each native site, while the second cohort was grown on the soil conditioned by the first. Our goal was to distinguish site-specific effects mediated by biotic and/or abiotic soil properties from those inherent in seed sources. Cohort 1 plants grown from seeds produced in small populations performed better in terms of germination, growth, and survival compared to plants produced in large populations. Plant performance decreased substantially between cohorts, indicating strong negative feedback. Most importantly, the strength of negative feedback scaled linearly (i.e., was less negative) with increasing size of the native plant population, particularly for germination and survival, and was better explained by soil- rather than seed-source effects. Even with a small number of sites, our results suggest that the potential for negative plant–soil feedback varies among populations of L. siphilitica, and that small populations were more susceptible to negative feedback. Conspecific plant–soil feedback may contribute to plant population size variation within a species’ native range.     

Hyperammonemia Alters the Function of AMPA and NMDA Receptors in Hippocampus: Extracellular cGMP Reverses Some of These Alterations

Neurochemical Research - Chronic hyperammonemia alters membrane expression of AMPA and NMDA receptors subunits in hippocampus leading to impaired memory and learning. Increasing extracellular cGMP...     

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.     

6-Amino-4-oxo-1,3-diphenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonyl derivatives as a new class of potent inhibitors of Interleukin-8-induced neutrophil chemotaxis

A series of 6-amino-4-oxo-1,3-diphenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonyl derivatives was synthesized. The compounds demonstrated to be novel, potent and selective inhibitors of Interleukin-8-induced human neutrophil chemotaxis. A SAR study was performed by varying the carbonyl function at position 5 and the chain linked to the amino group at position 6 of the scaffold. All the compounds of the series displayed inhibitory activity at nano- or picomolar concentrations against Interleukin-8-driven migration and no activity against fMLP- and C5a-induced chemotaxis. The binding tests of selected compounds on CXCR1 and CXCR2 receptors were negative. The most potent derivative showed in vivo efficacy in a mouse model of Zymosan-induced peritonitis.     

Structure-function relationship studies of PTH(1-11) analogues containing sterically hindered dipeptide mimetics.

The N-terminal 1-34 fragment of parathyroid hormone (PTH) is fully active in vitro and in vivo and reproduces all biological responses characteristic of the native intact PTH. In order to develop safer and non-parenteral PTH-like bone anabolic agents, we have studied the effect of introducing conformationally constrained dipeptide mimetics into the N-terminal portion of PTH in an effort to generate miniaturized PTH-mimetics. To this end, we have synthesized and conformationally and biologically characterized PTH(1-11) analogues containing 3R-carboxy-6S-amino-7,5-bicyclic thiazolidinlactam (7,5-bTL), a rigidified dipeptide mimetic unit. The wild type sequence of PTH(1-11) is H-Ser-Val-Ser-Glu-Ile-Gln-Leu-Met-His-Asn-Leu-NH(2). The following pseudo-undecapeptides were prepared: [Ala(1), 7,5-bTL(3, 4), Nle(8), Arg(11)]hPTH(1-11)NH(2) (I); [Ala(1), 7,5-bTL(6, 7), Nle(8), Arg(11)]hPTH(1-11)NH(2) (II); [Ala(1), Nle(8), 7,5-bTL(9, 10), Arg(11)]hPTH(1-11)NH(2) (III). In aqueous solution containing 20% TFE, only analogue I exhibited the typical CD pattern of the alpha-helical conformation. NMR experiments and molecular dynamics calculations located the alpha-helical stretch in the sequence Ile(5)-His(9). The dipeptide mimetic unit 7,5-bTL induces a type III beta-turn, occupying the positions i - 1 and i of the turn. Analogue II exhibited an equilibrium between a type I beta-turn and an alpha-helix, and analogue III did not show any ordered structure. Biological tests revealed poor activity for all analogues (EC(50) > 0.1 mM). Apparently, the relative side-chain orientation of Val(2), Ile(5) and Met(8) can be critical for effective analogue-receptor interaction. Considering helicity as an essential property to obtain active PTH agonists, one must decorate the correctly positioned dipeptide mimetic azabicycloalkane scaffold with substitutions corresponding to the displaced amino acids.     

Manganese activates the mitochondrial apoptotic pathway in rat astrocytes by modulating the expression of proteins of the Bcl-2 family

Manganese induces the central nervous system injury leading to manganism, by mechanisms not completely understood. Chronic exposure to manganese generates oxidative stress and induces the mitochondrial permeability transition. In the present study, we characterized apoptotic cell death mechanisms associated with manganese toxicity in rat cortical astrocytes and demonstrated that (i) Mn treatment targets the mitochondria and induces mitochondrial membrane depolarization followed by cytochrome c release to the cytoplasm, (ii) Mn induces both effector caspases 3/7 and 6 as well as PARP-1 cleavage and (iii) Mn shifts the balance of cell death/survival of Bcl-2 family proteins to favor the apoptotic demise of astrocytes. Our model system using cortical rat astrocytes treated with Mn would emerge as a good tool for investigations aimed to elucidate the role of apoptosis in manganism.     

HLA mismatches and hematopoietic cell transplantation: Structural simulations assess the impact of changes in peptide binding specificity on transplant outcome

The success of hematopoietic cell transplantation from an unrelated donor depends in part on the degree of Human Histocompatibility Leukocyte Antigen (HLA) matching between donor and patient. We present a structure-based analysis of HLA mismatching, focusing on individual amino acid mismatches and their effect on peptide binding specificity. Using molecular modeling simulations of HLA-peptide interactions, we find evidence that amino acid mismatches predicted to perturb peptide binding specificity are associated with higher risk of mortality in a large and diverse dataset of patient-donor pairs assembled by the International Histocompatibility Working Group in Hematopoietic Cell Transplantation consortium. This analysis may represent a first step toward sequence-based prediction of relative risk for HLA allele mismatches.     

Monoamine oxidases (MAO) in the pathogenesis of heart failure and ischemia/reperfusion injury

Recent evidence highlights monoamine oxidases (MAO) as another prominent source of oxidative stress. MAO are a class of enzymes located in the outer mitochondrial membrane, deputed to the oxidative breakdown of key neurotransmitters such as norepinephrine, epinephrine and dopamine, and in the process generate H₂O₂. All these monoamines are endowed with potent modulatory effects on myocardial function. Thus, when the heart is subjected to chronic neuro-hormonal and/or peripheral hemodynamic stress, the abundance of circulating/tissue monoamines can make MAO-derived H₂O₂ production particularly prominent. This is the case of acute cardiac damage due to ischemia/reperfusion injury or, on a more chronic stand, of the transition from compensated hypertrophy to overt ventricular dilation/pump failure. Here, we will first briefly discuss mitochondrial status and contribution to acute and chronic cardiac disorders. We will illustrate possible mechanisms by which MAO activity affects cardiac biology and function, along with a discussion as to their role as a prominent source of reactive oxygen species. Finally, we will speculate on why MAO inhibition might have a therapeutic value for treating cardiac affections of ischemic and non-ischemic origin. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.     

Trophic niche overlap and wild ungulate consumption by red fox and wolf in a mountain area in Italy

Red fox (Vulpes vulpes) and wolf (Canis lupus) are two widespread opportunistic predators living in simpatry in many areas. Nonetheless, scarce information are available on their trophic interactions. We investigated food habits of these two carnivores in a mountain area in Italy and assessed the extent of their trophic niche overlap, focusing on the consumption of wild ungulates. Thereby we analyzed the content of 669 red fox scats and 253 wolf scats collected between May 2008 and April 2009. Red foxes resulted to have a more than three times higher niche breadth than wolves. Vegetables, small mammals, wild ungulates, and invertebrates were major items (altogether 92% of volume) of the red fox annual diet. On the contrary wolf annual diet relied on wild ungulates (94% of volume) with wild boar (Sus scrofa) being the main food item. The degree of trophic niche overlap between the two species was found to be low (Pianka's O = 0.356). Diet variation between the warm and the cold seasons was limited in both species, and higher in red fox than in wolf. The two canids appeared to use wild ungulates unevenly being the former more selective for younger preys, smaller in size (newborn piglets and roe deer Capreolus capreolus fawns), whereas the latter exhibited a preference for medium-sized and large ungulates (10–35 kg wild boar and adult roe deer). Even if wild ungulates represent the main shared food category, the different use of age/weight classes by the two predators, together with their possible consumption as carrions by red fox, suggests a very limited trophic competition between wolf and red fox.This study represents a contribution to the knowledge of trophic interaction in predator–prey systems where sympatric carnivores are present.