From implantation to birth: insight into molecular melatonin functions

Melatonin is a lipophilic hormone synthesized and secreted mainly in the pineal gland, acting as a neuroendocrine transducer of photoperiodic information during the night. In addition to this activity, melatonin has shown an antioxidant function and a key role as regulator of physiological processes related to human reproduction. Melatonin is involved in the normal outcome of pregnancy, beginning with the oocyte quality, continuing with embryo implantation, and finishing with fetal development and parturition. Melatonin has been shown to act directly on several reproductive events, including folliculogenesis, oocyte maturation, and corpus luteum (CL) formation. The molecular mechanism of action has been investigated through several studies which provide solid evidence on the connections between maternal melatonin secretion and embryonic and fetal development. Melatonin administration, reducing oxidative stress and directly acting on its membrane receptors, melatonin thyroid hormone receptors (MT1 and MT2), displays effects on the earliest phases of pregnancy and during the whole gestational period. In addition, considering the reported positive effects on the outcomes of compromised pregnancies, melatonin supplementation should be considered as an important tool for supporting fetal development, opening new opportunities for the management of several reproductive and gestational pathologies

Novel Nicotinic Acetylcholine Receptor Ligands based on Cytisine, Ferruginine, Anatoxin-a and Choline : <i>In vitro </i>Evaluation and Structure-Activity Relationships

Nicotinic acetylcholine receptors (nAChRs), excitatory ligand-gated cation channels, are transmembranic allosteric proteins composed of five polypeptide chains. The subtype at the neuromuscular junction consists of α1, β1, γ and δ subunits whereas the neuronal subtypes are formed by a combination of different α (α2 to α10) and β(β2 to β4) subunits (heteromeric type) or identical α subunits (homomeric type). NAChRs are widely distributed in the central nervous system and in the periphery. In recent years, there has been increasing interest in nAChR ligands as potential analgesics and therapeutics for the treatment of various neurological and mental disorders related to a decrease in cholinergic function such as Alzheimer’s and Parkinson’s diseases, attention deficit/hyperactivity disorder, schizophrenia, and depression. Natural toxic alkaloids like (-)-cytisine, (+)-ferruginine, and (+)-anatoxin-a possess high affinity for α4β2 nAChR, representing the major population of nACh receptors in mammalian brain, but no appropriate selectivity. Structure-activity relationship studies for these ligands are missing for other subtypes, like α7, α3β4 and (α1)2β1γδ. In order to evaluate the affinities of novel analogues of (-)-cytisine, (+)-ferruginine, and (+)-anatoxin-a, in vitro radioligand binding studies were performed for four different nAChR subtypes: α4β2*, α7*, α3β4* and (α1)2β1γδ nAChRs, using membranes of native tissues (rat brains, calf/pig adrenals and Torpedo calif. electroplax). Important information could be obtained concerning the structural requirements that enhance selectivity of these novel analogues for α4β2* nAChR over other nAChRs investigated. In general, since the molecular recognition between ligands and nAChRs might be based on cation-pi interactions and a hydrogen bond formation between the receptor site and the ligand (HBD-HBA interaction), all high affinity compounds bear the cationic and HBA motifs. Beside the search and development of novel nAChR ligands exhibiting selectivity for the α4β2* nAChR, interest is growing to develop novel compounds selective for the α7 and α3-containing subtypes. Choline has proved to be a selective ligand for the α7, showing also neuroprotective actions. In this study, choline derivatives are evaluated in in vitro radioligand binding studies to gain more information about the structural requirements to enhance the selectivity for α7* versus the α4β2* nicotinic receptor

Long-term Relationships between Carbon Sequestration, Hydrology, and Tephra Disturbance in a Northern Peatland (Kamchatka Peninsula, Russia)

Northern peatlands are one of the most important carbon reservoirs, storing one-third to one-half of the world’s soil carbon pool and thus changes in their carbon balance have the potential to cause a positive feedback to climate change. While recent studies have made progress in understanding the climatic controls on the global carbon cycle, few have studied the important interaction between landscape disturbance (via volcanic eruptions), carbon accumulation, and peatland hydrology. Kamchatka Peninsula in the Russian Far East provides a unique opportunity to study long-term peatland hydrology and carbon accumulation with respect to the role of disturbance, as the area has been subjected to repeated landscape disturbance by tephra deposition over the last 10,000 years. In this study, I use a 10,000-year-old peatland record from Krutoberegovo, Kamchatka Peninsula (Russian Far East) to examine the interaction between carbon accumulation, peat surface wetness, and landscape disturbance in the form of peat surface burial by volcanic ash (tephra). I specifically ask whether tephra deposition affected the hydrological regime of the peatland, its nutrient status, and its ability to store carbon. To answer this question, I use a suite of palaeoecological and geochemical analyses as follows. First, I use 16 AMS 14C age measurements to create an absolute timescale for peatland development. Second, I use the peatland chronostratigraphy and measurements of peat carbon content to reconstruct the long-term carbon accumulation rates (LORCA). Third, I employ testate amoeba (TA) as a hydrological proxy to reconstruct peat surface wetness over time. Fourth, I reconstruct the nutrient status of the peatland by comparing the carbon to nitrogen ratios (C/N), where higher nitrogen values and lower carbon values are indicative of more nutrient-rich environments and vice versa. My results show that the Krutoberegovo peatland experienced thirty-four different tephra deposition events during the last 10,000 years, of which nine were considered major regional markers, based on their thickness, unique geochemical signatures, and area of dispersal. The carbon sequestration potential of the Krutoberegovo peatland measured as long-term apparent rates of carbon accumulation (LORCA) shows a wide variability over the course of the Holocene ranging from 74.5 g C m-2 yr-1 to 7.91 g C m-2 yr-1, with a substantial decrease in accumulation rates during periods of high tephra loading. Although the mechanisms responsible for this process remain unclear, I hypothesize that changes in carbon sequestration following tephra loading of peat surface could be mediated by changes in microbial activity and wetland vegetation cover. High-resolution analysis of testate amoebae (TA) communities over the course of the Holocene shows a high degree of variability with frequent shifts in taxa dominance. The statistical analysis of testate amoeba taxa in relation to tephra-related environmental variables (total ash content and major eruptions) shows that tephra deposition explains to a large degree the shifts in TA communities. Total ash content explains 77.3% of the taxa variability, while major volcanic eruptions as discrete events explain 6.3%. However, when TA communities are grouped according to their hydrological affinities, tephra deposition does not seem to affect any particular hydrological group suggesting that tephra disturbance does not play a role in peatland hydrology. Analysis of carbon and nitrogen chemistry of the Krutoberegovo peat profile suggest that tephra loading of the peat surface induced a net loss of both carbon and nitrogen. The C/N ratios – a measure of nutrient availability in peatland ecosystems – show a variable but overall increasing trend, which may be related to an autogenic replacement of nutrient rich with nutrient poor wetland plant communities. However, periods with lower or decreasing C/N ratios seem to be associated with high tephra loading, suggesting that tephra deposition may have also played a role

Craniofacial reconstruction as a prediction problem using a Latent Root Regression model

International audienceIn this paper, we present a computer-assisted method for facial reconstruction. This method provides an estimation of the facial shape associated with unidentified skeletal remains. Current computer-assisted methods using a statistical framework rely on a common set of extracted points located on the bone and soft-tissue surfaces. Most of the facial reconstruction methods then consist of predicting the position of the soft-tissue surface points, when the positions of the bone surface points are known. We propose to use Latent Root Regression for prediction. The results obtained are then compared to those given by Principal Components Analysis linear models. In conjunction, we have evaluated the influence of the number of skull landmarks used. Anatomical skull landmarks are completed iteratively by points located upon geodesics which link these anatomical landmarks, thus enabling us to artificially increase the number of skull points. Facial points are obtained using a mesh-matching algorithm between a common reference mesh and individual soft-tissue surface meshes. The proposed method is validated in term of accuracy, based on a leave-one-out cross-validation test applied to a homogeneous database. Accuracy measures are obtained by computing the distance between the original face surface and its reconstruction. Finally, these results are discussed referring to current computer-assisted reconstruction facial techniques

Antimicrobial and antibiofilm activity and machine learning classification analysis of essential oils from different mediterranean plants against pseudomonas aeruginosa

Pseudomonas aeruginosa is a ubiquitous organism and opportunistic pathogen that can cause persistent infections due to its peculiar antibiotic resistance mechanisms and to its ability to adhere and form biofilm. The interest in the development of new approaches for the prevention and treatment of biofilm formation has recently increased. The aim of this study was to seek new non-biocidal agents able to inhibit biofilm formation, in order to counteract virulence rather than bacterial growth and avoid the selection of escape mutants. Herein, different essential oils extracted from Mediterranean plants were analyzed for their activity againstP. aeruginosa. Results show that they were able to destabilize biofilm at very low concentration without impairing bacterial viability. Since the action is not related to a bacteriostatic/bactericidal activity onP. aeruginosa, the biofilm change of growth in presence of the essential oils was possibly due to a modulation of the phenotype. To this aim, application of machine learning algorithms led to the development of quantitative activity-composition relationships classification models that allowed to direct point out those essential oil chemical components more involved in the inhibition of biofilm production. The action of selected essential oils on sessile phenotype make them particularly interesting for possible applications such as prevention of bacterial contamination in the community and in healthcare environments in order to prevent human infections. We assayed 89 samples of different essential oils asP. aeruginosaanti-biofilm. Many samples inhibitedP. aeruginosabiofilm at concentrations as low as 48.8 µg/mL. Classification of the models was developed through machine learning algorithms

A new anti-infective strategy to reduce the spreading of antibiotic resistance by the action on adhesion-mediated virulence factors in Staphylococcus aureus.

Staphylococcus aureus is a flexible microbial pathogen frequently isolated from community-acquired and nosocomial infections. S. aureus expresses a wide array of secreted and cell surface-associated virulence factors, including proteins that promote adhesion to damaged tissue and to the surface of host cells, and that bind proteins in blood to help evade immune responses. Furthermore, surface proteins have a fundamental role in virulence related properties of S. aureus, including biofilm formation. The present study evaluates the anti-infective capabilities of a secreted protein of Serratia marcescens (serratiopeptidase, SPEP), in impairing some staphylococcal virulence-related properties, such as attachment to inert surfaces and adhesion/invasion on eukaryotic cells. SPEP seems to exert its action by modulating specific proteins. It is not assessed if this action is due to the proteolytic activity of SPEP or to a specific mechanism which triggers an out/inside signal. Proteomic studies performed on surface proteins extracted from SPEP treated S. aureus cultures revealed that a number of proteins are affected by the treatment. Among these we found the adhesin/autolysin Atl, SdrD, Sbi, EF-Tu and EF-G. EF-Tu and EF-G are known to perform a variety of function, depending on their cytoplasmic or surface localization. All these factors can facilitate bacterial colonization, persistence and invasion of host tissues. Our results suggest that SPEP could be developed as a potential "anti-infective agent" capable to hinder the entry of S. aureus into human tissues, and also impairs the ability of this pathogen to adhere to prostheses, catheters and medical device

Serratiopeptidase: a well-known metalloprotease with a new non-proteolytic activity against S. aureus biofilm

Background The use of indwelling medical devices is associated with a significant risk of infections by Staphylococcus aureus (S. aureus) which possesses a variety of virulence factors including many toxins and the ability to invade eukaryotic cells or to form biofilm on biotic and abiotic surfaces. The virulence factors above described are often related to proteins exposed on the bacterial surface. Blocking S. aureus colonization may reduce the incidence of invasive infectious diseases. Previously reports evaluated the anti-infective properties of serratiopeptidase (Spep), an extracellular metalloprotease produced by Serratia marcescens ATCC 21074 (E-15), in impairing virulence-related staphylococcal properties, such as attachment to inert surfaces and adhesion/invasion on eukaryotic cells. However, to date its mechanism of action is unknown. Methods Spep gene was PCR amplified and cloned into expression vector pET28b(+). The mutant EspepA was constructed from plasmid pET28b-Spep applying the one-step overlap extension PCR strategy. There sulting plasmids were costransformed in EcBL21(DE3) cells with the plasmid pRuW4inh1 harboring the Erwinia chrysanthemi secretion system. Bacterial pellets and supernatants were collected and analyzed by SDS-PAGE and zymography. The unambiguous identification and a detailed structure characterization of both the wild type and the mutant Spep were obtained by mass spectrometric analyses. The resultant supernatants sterilized by filtration were separately used to condition biofilm formation of S. aureus. Quantification was based on crystal violet method. Results In this work we constructed Spep mutant by substituting the glutamic acid in the catalytic site with a residue of alanine. In this manner we were able to evaluate the anti-biofilm activity of Spep mutant in absence of proteolytic activity. As expected, this mutant did not display protease activity but it retained its anti-biofilm properties, suggesting that this action is independent by enzymatic activity. Conclusions New knowledge obtained from data reported in this paper calls attention to a novel mechanism of action of Spep. This protein could be developed as a potential “antipathogenic agent” capable to impair the ability of S. aureus to form biofilm on prostheses, catheters and medical devices, exploiting a mechanism different from the proteolytic activity

Anti-Biofilm Activity of a Long-Chain Fatty Aldehyde from Antarctic Pseudoalteromonas haloplanktis TAC125 against Staphylococcus epidermidis Biofilm

Staphylococcus epidermidis is a harmless human skin colonizer responsible for ~20% of orthopedic device-related infections due to its capability to form biofilm. Nowadays there is an interest in the development of anti-biofilm molecules. Marine bacteria represent a still underexploited source of biodiversity able to synthesize a broad range of bioactive compounds, including anti-biofilm molecules. Previous results have demonstrated that the culture supernatant of Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 impairs the formation of S. epidermidis biofilm. Further, evidence supports the hydrophobic nature of the active molecule, which has been suggested to act as a signal molecule. In this paper we describe an efficient activity-guided purification protocol which allowed us to purify this anti-biofilm molecule and structurally characterize it by NMR and mass spectrometry analyses. Our results demonstrate that the anti-biofilm molecule is pentadecanal, a long-chain fatty aldehyde, whose anti-S. epidermidis biofilm activity has been assessed using both static and dynamic biofilm assays. The specificity of its action on S. epidermidis biofilm has been demonstrated by testing chemical analogs of pentadecanal differing either in the length of the aliphatic chain or in their functional group properties. Further, indications of the mode of action of pentadecanal have been collected by studying the bioluminescence of a Vibrio harveyi reporter strain for the detection of autoinducer AI-2 like activities. The data collected suggest that pentadecanal acts as an AI-2 signal. Moreover, the aldehyde metabolic role and synthesis in the Antarctic source strain has been investigated. To the best of our knowledge, this is the first report on the identification of an anti-biofilm molecule form from cold-adapted bacteria and on the action of a long-chain fatty aldehyde acting as an anti-biofilm molecule against S. epidermidis