Unlocking ground-based imagery for habitat mapping.

Fine-grained environmental data across large extents are needed to resolve the processes that impact species communities from local to global scales. Ground-based images (GBIs) have the potential to capture habitat complexity at biologically relevant spatial and temporal resolutions. Moving beyond existing applications of GBIs for species identification and monitoring ecological change from repeat photography, we describe promising approaches to habitat mapping, leveraging multimodal data and computer vision. We illustrate empirically how GBIs can be applied to predict distributions of species at fine scales along Street View routes, or to automatically classify and quantify habitat features. Further, we outline future research avenues using GBIs that can bring a leap forward in analyses for ecology and conservation with this underused resource.

Catchment properties and the photosynthetic trait composition of freshwater plant communities.

Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO2) to compensate for the low diffusivity and potential depletion of CO2 in water. Concentrations of bicarbonate and CO2 vary greatly with catchment geology. In this study, we investigate whether there is a link between these concentrations and the frequency of freshwater plants possessing the bicarbonate use trait. We show, globally, that the frequency of plant species with this trait increases with bicarbonate concentration. Regionally, however, the frequency of bicarbonate use is reduced at sites where the CO2 concentration is substantially above the air equilibrium, consistent with this trait being an adaptation to carbon limitation. Future anthropogenic changes of bicarbonate and CO2 concentrations may alter the species compositions of freshwater plant communities.

Hemostatic alterations in patients with benign and malignant colorectal disease during major abdominal surgery.

We determined sensitive markers of coagulation and fibrinolysis in plasma of 20 patients with malignant colorectal disease as compared to 17 patients with benign colorectal disease. Thrombin/antithrombin III complex (TAT), soluble fibrin (SF), total fibrinogen and fibrin degradation products (TDP), plasminogen activator inhibitor type-1 (PAI-1), urokinase-type plasminogen activator (uPA) and uPA receptor (uPAR) were measured preoperatively, starting anesthesia, during surgery and postoperatively. The purpose was to verify the supposed hypercoagulable state of cancer patients. In addition, we investigated whether the hemostatic alterations induced by general anesthesia and major abdominal surgery differed between the two groups. Patients with colorectal cancer showed initially an altered balance of hemostasis with a preponderance of procoagulant activity and fibrinolytic inhibition, as noted by marginally elevated TAT and PAI-1 plasma levels. The stimulus of anesthesia induction alone was sufficient to trigger not only activation of coagulation in these patients but also further activation of fibrinolysis and increased fibrinolytic inhibition. The marked activation of coagulation and fibrinolysis and enhanced fibrinolytic inhibition during surgery was more pronounced in patients with malignancy as compared to the control group. Postoperatively, a shift of the normal balance of hemostasis with a slight preponderance of fibrinolytic inhibition was observed, as evidenced by a marginally elevated PAI-1 plasma levels. The results of this study strengthen the hypothesis of a hypercoagulable state in patients with colorectal malignancy that may favor the development of thrombosis in this patient group.

Biological properties of the benzodiazepine amidine derivative L-740,093, a cholecystokinin-B/gastrin receptor antagonist with high affinity in vitro and high potency in vivo.

A novel series of 5-amino-1,4-benzodiazepin-2-one derivatives (amidines), which contain a cationic solubilizing group and which are antagonists for the cholecystokinin (CCK)-B receptor, have been identified. Optimization of this series led to the identification of an azabicyclononane amidine, L-740,093 [N-[(3R)-5-(3-azabicyclo[3.2.2]nonan-3-yl)-2,3-dihydro-1-methyl-2- oxo- 1H-1,4-benzodiazepin-3-yl]-N'-(3-methylphenyl)urea], that bound with high affinity of CCK-B receptors from guinea pig cerebral cortex (IC50 of 0.1 nM) and had a CCK-B/CCK-A receptor selectivity of 16,000. In comparison, L-365,260 had 85-fold lower affinity (8.5 nM) and was only 87-fold selective for CCK-B over CCK-A receptors. L-740,093 bound with high affinity to guinea pig gastrin receptors in vitro (IC50 of 0.04 nM). Electrophysiological studies on slices of rat ventromedial hypothalamic nucleus showed that L-740,093 produced rightward shifts of the concentration-response curve for the CCK-B receptor agonist pentagastrin (Kb of 0.06 nM). L-740,093 blocked pentagastrin-induced gastric acid secretion in anesthetized rats with a 50% inhibitory dose of 0.01 mg/kg, intraperitoneally, showing 100-fold greater activity, compared with L-365,260 (50% inhibitory dose of 1 mg/kg, intraperitoneally). An ex vivo binding assay in mice was used to investigate the interaction of L-740,093 with central CCK binding sites. After intravenous administration, L-740,093 inhibited ex vivo binding dose dependently, with a 50% effective dose of 0.2 mg/kg. These studies demonstrate that L-740,093 is the most potent and selective CCK-B antagonist yet described and that it has excellent central nervous system penetration.

Mechanism of inositol monophosphatase, the putative target of lithium therapy.

myo-Inositol monophosphatase (myo-inositol-1-phosphate phosphohydrolase, EC 3.1.3.25) is an attractive target for mechanistic investigation due to its critical role in the phosphatidylinositol signaling pathway and the possible relevance of its inhibition by Li+ to manic depression therapy. The x-ray crystallographic structure of human inositol monophosphatase in the presence of the inhibitory metal Gd3+ showed only one metal bound per active site, whereas in the presence of Mn2+, three ions were present with one being displaced upon phosphate binding. We report here modeling, kinetic, and mutagenesis studies on the enzyme, which reveal the requirement for two metal ions in the catalytic mechanism. Activity titration curves with Zn2+ or Mn2+ in the presence or absence of Mg2+ are consistent with a two-metal mechanism. Modeling studies based on the various x-ray crystallographic structures (including those with Gd3+ and substrate bound) further support a two-metal mechanism and define the positions of the two metal ions relative to substrate. While the first metal ion may activate water for nucleophilic attack, a second metal ion, coordinated by three aspartate residues, appears to act as a Lewis acid, stabilizing the leaving inositol oxyanion. In this model, the 6-OH group of substrate acts as a ligand for this second metal ion, consistent with the reduced catalytic activity observed with substrate analogues lacking the 6-OH. Evidence from Tb3+ fluorescence quenching and the two-metal kinetic titration curves suggests that Li+ binds at the site of this second metal ion.

Inhibition of PC12 cell redox activity is a specific, early indicator of the mechanism of beta-amyloid-mediated cell death.

An in vitro tissue culture cell model system for investigating the biochemical mechanisms involved in the neurodegenerative actions of beta-amyloid has been established. Using rat pheochromocytoma PC12 cells, it was found that an early, specific response of cells to the beta-amyloid protein or the beta-amyloid fragment 25-35 was a potent inhibition of cellular redox activity, as measured by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) reduction. This inhibitory response was rapid and occurred at nanomolar concentrations of peptide, concentrations at which no equivalent decreases in cell proliferation or cell survival were observed. The inhibition of PC12 cell MTT reduction was initially reversible upon removal of the peptide; if sustained for several days, however, by repeated peptide application, it became associated with a dramatic reduction in cell survival. Inhibition of MTT reduction may, therefore, be an early indicator of the mechanism of beta-amyloid-mediated cell death.

Neuroprotective NMDA antagonists: the controversy over their potential for adverse effects on cortical neuronal morphology.

It has been reported that several uncompetitive NMDA receptor ion channel blocking agents (phencyclidine, ketamine, dizocilpine, dextrorphan) cause transient reversible vacuolation in neurons in the posterior cingulate cortex of rats. Similar effects have also been observed with competitive glutamate antagonists such as CPP, CGS 19755 and CGP 37849. This transient morphological change has been noted to be coincident anatomically with brain regions showing hypermetabolism after administration of uncompetitive NMDA receptor ion channel blockers and competitive glutamate antagonists. These results therefore indicate that the functional consequences of NMDA receptor blockade with competitive glutamate and uncompetitive channel antagonists are ultimately the same. These changes do not appear to be a prelude to irreversible damage except after relatively high doses of the receptor ion channel antagonists but they have given rise to concern over the safety in use of NMDA antagonists as neuroprotective agents. In contrast, vacuolation has not yet been demonstrated with agents acting at the glycine (L-687,414) or polyamine (eliprodil) modulatory sites of the NMDA receptor complex suggesting that agents acting at these sites may have a greater potential therapeutic window.

Competitive as well as uncompetitive N-methyl-D-aspartate receptor antagonists affect cortical neuronal morphology and cerebral glucose metabolism.

The studies examined the effects of three antagonists (CPP, CGS 19755, and CGP 37849) that act competitively at the glutamate recognition site of the NMDA receptor complex on cortical neuronal morphology and cerebral limbic glucose metabolism. Responses were compared to the effects of dizocilpine, an uncompetitive NMDA receptor ion channel antagonist as a positive control. CGS 19755 and CGP 37849 (100 mg kg-1 i.p.) caused vacuolation in cortical pyramidal neurons in the posterior cingulate cortex four hours after dosing and this dose of CGP 37849 caused a pattern of limbic glucose metabolism activation similar to that seen after dizocilpine. CPP was without effect at 100 mg/kg i.p. probably due to poor brain penetration. The data indicates that the functional consequences (structural and metabolic) of NMDA receptor blockade with NMDA antagonists acting competitively at the glutamate recognition site and uncompetitively in the receptor ion channel are ultimately the same. Comparisons of the potential therapeutic window for CGS 19755 and CGP 37849 with dizocilpine (neuroprotection versus vacuolation) suggests that the window for the competitive antagonists is greater. This indicates that the potential therapeutic window for the different classes of NMDA antagonists may vary with the site in the receptor complex at which they interact.

The design of novel muscarinic partial agonists that have functional selectivity in pharmacological preparations in vitro and reduced side-effect profile in vivo.

Antagonist/agonist binding ratios (NMS/Oxo-M ratio) were used as an index of the efficacy of novel compounds acting at muscarinic receptors. These binding ratios have been used with a range of functional pharmacological assays to investigate the effects of varying the efficacy of muscarinic agonists. This strategy has been used as a means of obtaining functional receptor selectivity by exploiting differences in effective receptor reserves. The oxadiazole and pyrazine muscarinic agonists L-670,548 (NMS/Oxo-M ratio 1100) and L-680,648 (NMS/Oxo-M ratio 690) are amongst some of the most potent and efficacious agonists known. Decreasing the efficacy of compounds from these series, resulted in compounds with functional selectivity. The chloropyrazine L-689,660 (NMS/Oxo-M ratio 28) was an agonist on the rat superior cervical ganglion (M1), a partial agonist on the guinea-pig ileum (M3), but was an antagonist in the guinea-pig atria (M2). Synthesis of compounds with even lower predicted efficacy, such as the cyclopropyloxadiazole L-687,306 (NMS/Oxo-M ratio 15), maintained agonist activity in the ganglion, but showed antagonist activity in the M3 ileal, as well as the M2 atrial preparations. When tested in vivo these compounds did not produce many of the side effects associated with more efficacious agonists, particularly those associated with the cardiovascular system. However, they were active in reversing scopolamine-induced deficits in a variety of behavioural paradigms. This approach shows how functional selectivity for muscarinic receptor subtypes can be achieved in vitro, that in vivo reduces the dose-limiting side effects normally associated with muscarinic agonists.