Opioid treatment of pain is generally safe with 0.5% or less events from respiratory depression. However, fatalities are regularly reported. The only treatment currently available to reverse opioid ...respiratory depression is by naloxone infusion. The efficacy of naloxone depends on its own pharmacological characteristics and on those (including receptor kinetics) of the opioid that needs reversal. Short elimination of naloxone and biophase equilibration half-lives and rapid receptor kinetics complicates reversal of high-affinity opioids. An opioid with high receptor affinity will require greater naloxone concentrations and/or a continuous infusion before reversal sets in compared with an opioid with lower receptor affinity. The clinical approach to severe opioid-induced respiratory depression is to titrate naloxone to effect and continue treatment by continuous infusion until chances for renarcotization have diminished. New approaches to prevent opioid respiratory depression without affecting analgesia have led to the experimental application of serotinine agonists, ampakines, and the antibiotic minocycline.
Ectomycorrhizal (ECM) associations were historically considered rare or absent from tropical ecosystems. Although most tropical forests are dominated by arbuscular mycorrhizal (AM) trees, ECM ...associations are widespread and found in all tropical regions. Here, we highlight emerging patterns of ECM biogeography, diversity and ecosystem functions, identify knowledge gaps, and offer direction for future research. At the continental and regional scales, tropical ECM systems are highly diverse and vary widely in ECM plant and fungal abundance, diversity, composition and phylogenetic affinities. We found strong regional differences among the dominant host plant families, suggesting that biogeographical factors strongly influence tropical ECMsymbioses. BothECMplants and fungi also exhibit strong turnover along altitudinal and soil fertility gradients, suggesting niche differentiation among taxa. Ectomycorrhizal fungi are often more abundant and diverse in sites with nutrient-poor soils, suggesting that ECM associations can optimize plant nutrition and may contribute to the maintenance of tropical monodominant forests. More research is needed to elucidate the diversity patterns of ECM fungi and plants in the tropics and to clarify the role of this symbiosis in nutrient and carbon cycling.
Opioids induce respiratory depression via activation of μ-opioid receptors at specific sites in the central nervous system including the pre-Bötzinger complex, a respiratory rhythm generating area in ...the pons. Full opioid agonists like morphine and fentanyl affect breathing with onset and offset profiles that are primarily determined by opioid transfer to the receptor site, while the effects of partial opioid agonists such as buprenorphine are governed by transfer to the receptor site together with receptor kinetics, in particular dissociation kinetics. Opioid-induced respiratory depression is potentially fatal but may be reversed by the opioid receptor antagonist naloxone, an agent with a short elimination half-life (30 min). The rate-limiting factor in naloxone-reversal of opioid effect is the receptor kinetics of the opioid agonists that requires reversal. Agents with slow dissociation kinetics (buprenorphine) require a continuous naloxone infusion while agents with rapid kinetics (fentanyl) will show complete reversal upon a single naloxone dose. Since naloxone is non-selective and will reverse analgesia as well, efforts are focused on the development of compounds that reverse opioid-induced respiratory depression without affecting analgesic efficacy. Such agents include ampakines and serotonin agonists which are aimed at selectively enhancing central respiratory drive. A novel approach is aimed at the reduction of respiratory depression from opioid-activation of (micro-)glia cells in the pons and brainstem using micro-glia cell stabilizers. Since this approach simultaneously enhances opioid analgesic efficacy it seems an attractive alternative to the classical reversal strategies with naloxone.
Global species richness patterns of soil micro‐organisms remain poorly understood compared to macro‐organisms. We use a global analysis to disentangle the global determinants of diversity and ...community composition for ectomycorrhizal (EcM) fungi—microbial symbionts that play key roles in plant nutrition in most temperate and many tropical forest ecosystems. Host plant family has the strongest effect on the phylogenetic community composition of fungi, whereas temperature and precipitation mostly affect EcM fungal richness that peaks in the temperate and boreal forest biomes, contrasting with latitudinal patterns of macro‐organisms. Tropical ecosystems experience rapid turnover of organic material and have weak soil stratification, suggesting that poor habitat conditions may contribute to the relatively low richness of EcM fungi, and perhaps other soil biota, in most tropical ecosystems. For EcM fungi, greater evolutionary age and larger total area of EcM host vegetation may also contribute to the higher diversity in temperate ecosystems. Our results provide useful biogeographic and ecological hypotheses for explaining the distribution of fungi that remain to be tested by involving next‐generation sequencing techniques and relevant soil metadata.
See also the Perspective by Kennedy et al
Ectomycorrhizal (ECM) plants and fungi can be diverse and abundant in certain tropical ecosystems. For example, the primarily paleotropical ECM plant family Dipterocarpaceae is one of the most ...speciose and ecologically important tree families in Southeast Asia. Pakaraimaea dipterocarpacea is one of two species of dipterocarp known from the Neotropics, and is also the only known member of the monotypic Dipterocarpaceae subfamily Pakaraimoideae. This Guiana Shield endemic is only known from the sandstone highlands of Guyana and Venezuela. Despite its unique phylogenetic position and unusual geographical distribution, the ECM fungal associations of P. dipterocarpacea are understudied throughout the tree's range. In December 2010 we sampled ECM fungi on roots of P. dipterocarpacea and the co-occurring ECM tree Dicymbe jenmanii (Fabaceae subfamily Caesalpinioideae) in the Upper Mazaruni River Basin of Guyana. Based on ITS rDNA sequencing we documented 52 ECM species from 11 independent fungal lineages. Due to the phylogenetic distance between the two host tree species, we hypothesized that P. dipterocarpacea would harbor unique ECM fungi not found on the roots of D. jenmanii. Although statistical tests suggested that several ECM fungal species did exhibit host preferences for either P. dipterocarpacea or D. jenmanii, most of the ECM fungi were multi-host generalists. We also detected several ECM fungi that have never been found in long-term studies of nearby rainforests dominated by other Dicymbe species. One particular mushroom-forming fungus appears to be unique and may represent a new ECM lineage of Agaricales that is endemic to the Neotropics.
The ectomycorrhizal (ECM) symbiosis was historically considered restricted to the temperate zones, but recent studies have shown the importance of this symbiosis across the tropics. We examined ECM ...fungal diversity, host plant phylogeny and ECM host preferences in a rainforest dominated by the leguminous host plants Dicymbe corymbosa, Dicymbe altsonii and Aldina insignis. Ectomycorrhizal fungi were identified by internal transcribed spacer rDNA sequencing and host species were verified with chloroplast trnL sequencing. To test whether Dicymbe and Aldina represent independent gains of the ECM symbiosis, we constructed a Fabaceae phylogeny using MatK and trnL. We identified four independent ECM lineages within the Fabaceae. We detected a diverse community of 118 ECM species dominated by the /clavulina, /russula-lactarius, /boletus, and /tomentella-thelephora lineages. Ectomycorrhizal species in Agahcales, Atheliales and Polyporales may represent previously unrecognized tropical-endemic ECM lineages. Previous studies suggested that ECM fungi did not diversify in the tropics, but the /clavulina lineage appears to have a center of diversity in tropical South America. Dicymbe and Aldina represent independent gains of the ECM symbiosis in Fabaceae but their fungal symbionts showed no host preferences. Spatial factors are more important than hosts in structuring the ECM fungal community in this ecosystem.
The inability to quantify large numbers of proteins in tissues and biofluids with high precision, sensitivity, and throughput is a major bottleneck in biomarker studies. We previously demonstrated ...that coupling immunoaffinity enrichment using anti-peptide antibodies (SISCAPA) to multiple reaction monitoring mass spectrometry (MRM-MS) produces Immunoprecipitation MRM-MS (immuno-MRM-MS) assays that can be multiplexed to quantify proteins in plasma with high sensitivity, specificity, and precision. Here we report the first systematic evaluation of the interlaboratory performance of multiplexed (8-plex) immuno-MRM-MS in three independent labs. A staged study was carried out in which the effect of each processing and analysis step on assay coefficient of variance, limit of detection, limit of quantification, and recovery was evaluated. Limits of detection were at or below 1 ng/ml for the assayed proteins in 30 μl of plasma. Assay reproducibility was acceptable for verification studies, with median intra- and interlaboratory coefficients of variance above the limit of quantification of 11% and <14%, respectively, for the entire immuno-MRM-MS assay process, including enzymatic digestion of plasma. Trypsin digestion and its requisite sample handling contributed the most to assay variability and reduced the recovery of target peptides from digested proteins. Using a stable isotope-labeled protein as an internal standard instead of stable isotope-labeled peptides to account for losses in the digestion process nearly doubled assay accuracy for this while improving assay precision 5%. Our results demonstrate that multiplexed immuno-MRM-MS can be made reproducible across independent laboratories and has the potential to be adopted widely for assaying proteins in matrices as complex as plasma.
A SISCAPA (stable isotope standards and capture by anti-peptide antibodies) method for specific antibody-based capture of
individual tryptic peptides from a digest of whole human plasma was developed ...using a simplified magnetic bead protocol and
a novel rotary magnetic bead trap device. Following off-line equilibrium binding of peptides by antibodies and subsequent
capture of the antibodies on magnetic beads, the bead trap permitted washing of the beads and elution of bound peptides inside
a 150-μm-inner diameter capillary that forms part of a nanoflow LC-MS/MS system. The bead trap sweeps beads against the direction
of liquid flow using a continuous succession of moving high magnetic field-gradient trap regions while mixing the beads with
the flowing liquid. This approach prevents loss of low abundance captured peptides and allows automated processing of a series
of SISCAPA reactions. Selected tryptic peptides of α 1 -antichymotrypsin and lipopolysaccharide-binding protein were enriched relative to a high abundance serum albumin peptide
by 1,800 and 18,000-fold, respectively, as measured by multiple reaction monitoring. A large majority of the peptides that
are bound nonspecifically in SISCAPA reactions were shown to bind to components other than the antibody ( e.g. the magnetic beads), suggesting that substantial improvement in enrichment could be achieved by development of improved inert
bead surfaces.
The gastrointestinal (GI) peptide gastrin is an important regulator of the release of gastric acid from the stomach parietal cells and it also plays an important role in growth of the ...gastrointestinal tract. It has become apparent that gastrin and its related peptide cholecystokinin (CCK) are also significantly involved with growth of GI cancers as well as other malignancies through activation of the cholecystokinin-B (CCK-B) receptor. Of interest, gastrin is expressed in the embryologic pancreas but not in the adult pancreas; however, gastrin becomes re-expressed in pancreatic cancer where it stimulates growth of this malignancy by an autocrine mechanism. Strategies to down-regulate gastrin or interfere with its interface with the CCK receptor with selective antibodies or receptor antagonists hold promise for the treatment of pancreatic cancer and other gastrin--responsive tumors.
The tropics were long considered to have few ectomycorrhizal fungi, presumably due to a paucity of ectomycorrhizal host plants relative to higher-latitude ecosystems. However, an increase in research ...in tropical regions over the past 30 years has greatly expanded knowledge about the occurrence of tropical ectomycorrhizal fungi. To assess their broad biogeographic and diversity patterns, we conducted a comprehensive review and quantitative data analysis of 49 studies with 80 individual data sets along with additional data from GlobalFungi to elucidate tropical diversity patterns and biogeography of ectomycorrhizal fungi across the four main tropical regions: the Afrotropics, the Neotropics, Southeast Asia, and Oceania. Generalized linear models were used to explore biotic and abiotic influences on the relative abundance of the 10 most frequently occurring lineages. We also reviewed the available literature and synthesized current knowledge about responses of fungi to anthropogenic disturbances, and their conservation status and threats. We found that /russula-lactarius and /tomentella-thelephora were the most abundant lineages in the Afrotropics, the Neotropics, and Southeast Asia, whereas /cortinarius was the most abundant lineage in Oceania, and that /russula-lactarius, /inocybe, and /tomentella-thelephora were the most species-rich lineages across all of the tropical regions. Based on these analyses, we highlight knowledge gaps for each tropical region. Increased sampling of tropical regions, collaborative efforts, and use of molecular methodologies are needed for a more comprehensive view of the ecology and diversity of tropical ectomycorrhizal fungi.
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