Work-leave rotation pattern and incidence of offshore workplace injury.

Background: Studies on work-leave rotation pattern and work place injuries among offshore oil and gas workers have been few and limited to a 2- or 3-week rotation schedule. Aims: To examine incidence of workplace injury in relation to the duration of time into work rotation for extended work schedules up to 24 weeks. Methods: Six-year injury data on four offshore installations were extracted. Data were analysed for incidence of injury over time and relative risk using linear trend lines and regression. Results: In total, 311 injuries for 1302 workers were analysed, 39% with rotation schedule of 4 weeks work and 4 weeks rest, 27% 8 weeks work and 4 weeks rest, 23% 16 weeks work and 4 weeks rest and 10% 24 weeks work and 4 weeks rest. Incidence of injury decreased as duration of time into the work rotation increased, corrected for exposure, and this was statistically significant for all rotations in first 4 weeks (P < 0.01). Negative correlation between time offshore and injury was observed in all schedules and consistent for age groups, categories of work, shifts and severity of injury. There was no difference in relative risk of injuries between the four schedules, when corrected for exposure and occupational risk of injury. Conclusions: These results are at variance with previous studies, although no prior study has looked beyond 3-week rotation schedule. Longer offshore schedules are safely possible and this could help decrease manpower and logistics costs for oil and gas companies coping with unprecedented low oil prices.

Impact of a single-day multidisciplinary clinic on the management of patients with liver tumours.

PURPOSE: Multidisciplinary cancer clinics may improve patient care. We examined how a single-day multidisciplinary liver clinic (mdlc) affected care recommendations for patients compared with the recommendations provided before presentation to the mdlc. METHODS: We analyzed the demographic and clinicopathologic data of 343 patients assessed in the Johns Hopkins Liver Tumor Center from 2009 to 2012, comparing imaging and pathology interpretation, diagnosis, and management plan between the outside provider (osp) and the mdlc. RESULTS: Most patients were white (n = 259, 76%); median age was 60 years; and 146 were women (43%). Outside providers referred 182 patients (53%); the rest were self-referred. Patients travelled median of 83.4 miles (interquartile range: 42.7-247 miles). Most had already undergone imaging (n = 338, 99%) and biopsy (n = 194, 57%) at the osp, and a formal management plan had been formulated for about half (n = 168, 49%). Alterations in the interpretation of imaging occurred for 49 patients (18%) and of biopsy for 14 patients (10%). Referral to the mdlc resulted in a change of diagnosis in 26 patients (8%), of management plan in 70 patients (42%), and of tumour resectability in 7 patients (5%). Roughly half the patients (n = 174, 51%) returned for a follow-up, and 154 of the returnees (89%) received treatment, primarily intraarterial therapy (n = 88, 57%), systemic chemotherapy (n = 60, 39%), or liver resection (n = 32, 21%). Enrollment in a clinical trial was proposed to 34 patients (10%), and 21 of the 34 (62%) were accrued. CONCLUSIONS: Patient assessment by our multidisciplinary liver clinic had a significant impact on management, resulting in alterations to imaging and pathology interpretation, diagnosis, and management plan. The mdlc is an effective and convenient means of delivering expert opinion about the diagnosis and management of liver tumours.

Proteome size reduction in Apicomplexans is linked with loss of DNA repair and host redundant pathways.

Apicomplexans are alveolate parasites which include Plasmodium falciparum, the main cause of malaria, one of the world's biggest killers from infectious disease. Apicomplexans are characterized by a reduction in proteome size, which appears to result from metabolic and functional simplification, commensurate with their parasitic lifestyle. However, other factors may also help to explain gene loss such as population bottlenecks experienced during transmission, and the effect of reducing the overall genomic information content. The latter constitutes an 'informational constraint', which is proposed to exert a selective pressure to evolve and maintain genes involved in informational fidelity and error correction, proportional to the quantity of information in the genome (which approximates to proteome size). The dynamics of gene loss was examined in 41 Apicomplexan genomes using orthogroup analysis. We show that loss of genes involved in amino acid metabolism and steroid biosynthesis can be explained by metabolic redundancy with the host. We also show that there is a marked tendency to lose DNA repair genes as proteome size is reduced. This may be explained by a reduction in size of the informational constraint and can help to explain elevated mutation rates in pathogens with reduced genome size. Multiple Sequentially Markovian Coalescent (MSMC) analysis indicates a recent bottleneck, consistent with predictions generated using allele-based population genetics approaches, implying that relaxed selection pressure due to reduced population size might have contributed to gene loss. However, the non-randomness of pathways that are lost challenges this scenario. Lastly, we identify unique orthogroups in malaria-causing Plasmodium species that infect humans, with a high proportion of membrane associated proteins. Thus, orthogroup analysis appears useful for identifying novel candidate pathogenic factors in parasites, when there is a wide sample of genomes available.

The incidence of dry chlorhexidine gluconate transfer from skin to surgical gloves: a simulation and in vitro study.

BACKGROUND: To prevent alcohol-based chlorhexidine from reaching the cerebrospinal fluid, it is recommended that the antiseptic solution be allowed to dry before skin palpation or puncture. However, no guidelines specify a drying time interval. Manufacturers recommend 3 min of air drying, based upon the isopropyl alcohol component. Therefore, to fill this knowledge gap, we designed a simulation study to investigate the incidence of primary chlorhexidine transfer from skin to gloves following three drying time intervals. We also investigated the incidence of secondary chlorhexidine transfer from gloves to another surface following one drying time interval. METHODS: An alcohol-based chlorhexidine antiseptic solution with dye, ChloraPrep®, was applied to the skin of the lumbar region of 20 volunteers. Cotton-tipped applicators wrapped in material from gloves were taken from the application area at 3, 4, 5, and 10 min following application. Transfer of chlorhexidine from skin to gloves, and gloves to another medium, was assessed through a chemical assay that produced a color change when chlorhexidine was present on the sample. RESULTS: The incidence of primary chlorhexidine transfer from skin to gloves at 3, 4 and 10 min following application was 99.5%, 99.4%, and 99.6%, respectively. The incidence of secondary chlorhexidine transfer from gloves to another surface was 68.9%. CONCLUSION: Gloves are routinely contaminated with chlorhexidine during central neuraxial blockade. The high incidence of secondary transfer in our simulation suggests a pathway by which chlorhexidine may gain access to the neuraxial space.

Synergism between the Black Queen effect and the proteomic constraint on genome size reduction in the photosynthetic picoeukaryotes.

The photosynthetic picoeukaryotes (PPEs) comprise a rare example of free-living eukaryotes that have undergone genome reduction. Here, we examine a duality in the process; the proposed driver of genome reduction (the Black Queen hypothesis, BQH), and the resultant impact of genome information loss (the Proteomic Constraint hypothesis, PCH). The BQH predicts that some metabolites may be shared in the open ocean, thus driving loss of redundant metabolic pathways in individual genomes. In contrast, the PCH predicts that as the information content of a genome is reduced, the total mutation load is also reduced, leading to loss of DNA repair genes due to the resulting reduction in selective constraint. Consistent with the BQH, we observe that biosynthetic pathways involved with soluble metabolites such as amino acids and carotenoids are preferentially lost from the PPEs, in contrast to biosynthetic pathways involved with insoluble metabolites, such as lipids, which are retained. Consistent with the PCH, a correlation between proteome size and the number of DNA repair genes, and numerous other informational categories, is observed. While elevated mutation rates resulting from the loss of DNA repair genes have been linked to reduced effective population sizes in intracellular bacteria, this remains to be established. This study shows that in microbial species with large population sizes, an underlying factor in modulating their DNA repair capacity appears to be information content.

An effective CTL peptide vaccine for Ebola Zaire Based on Survivors' CD8+ targeting of a particular nucleocapsid protein epitope with potential implications for COVID-19 vaccine design.

The 2013-2016 West Africa EBOV epidemic was the biggest EBOV outbreak to date. An analysis of virus-specific CD8+ T-cell immunity in 30 survivors showed that 26 of those individuals had a CD8+ response to at least one EBOV protein. The dominant response (25/26 subjects) was specific to the EBOV nucleocapsid protein (NP). It has been suggested that epitopes on the EBOV NP could form an important part of an effective T-cell vaccine for Ebola Zaire. We show that a 9-amino-acid peptide NP44-52 (YQVNNLEEI) located in a conserved region of EBOV NP provides protection against morbidity and mortality after mouse adapted EBOV challenge. A single vaccination in a C57BL/6 mouse using an adjuvanted microsphere peptide vaccine formulation containing NP44-52 is enough to confer immunity in mice. Our work suggests that a peptide vaccine based on CD8+ T-cell immunity in EBOV survivors is conceptually sound and feasible. Nucleocapsid proteins within SARS-CoV-2 contain multiple Class I epitopes with predicted HLA restrictions consistent with broad population coverage. A similar approach to a CTL vaccine design may be possible for that virus.

A series of biotinylated tracers distinguishes three types of gap junction in retina.

Gap junctions serve many important roles in various tissues, but their abundance and diversity in neurons is only beginning to be understood. The tracer Neurobiotin has revealed many different networks interconnected by gap junctions in retina. We compared the relative permeabilities of five different retinal gap junctions by measuring their permeabilities to a series of structurally related tracers. When large tracers were injected, the staining of coupled cells fell off more rapidly in some networks than others relative to Neurobiotin controls. Three distinctly different permeability profiles were found, suggesting that multiple neuronal connexin types were present. The most permeant to large molecules were gap junctions from A-type horizontal cells. The permeability of gap junctions of two types of amacrine cell were not distinguishable from those from B-type horizontal cells. The lowest permeability was found for gap junctions between cone bipolar cells and the AII amacrine cells to which they are coupled. Because only a single neural connexin type has been identified in retina, our results suggest more types remain to be found. To determine whether the unitary permeability of channels is altered by channel modulators, we reduced permeability with octanol and a cAMP analog. Although net permeability was substantially diminished, the proportion by which it declined was constant across tracer size. This suggests that these agents act only to close channels rather than alter individual channel permeabilities. This tracer series can therefore be used to contrast permeability properties of gap junctions in intact circuits, even at the level of individual channels.

Morphology of bipolar cells labeled by DAPI in the rabbit retina.

The morphology, distribution, and coverage of certain cone bipolar cell types were investigated in rabbit retina. Brief in vitro incubation of isolated rabbit retina in the fluorescent dye 4,6-diamino-2-phenylindole labeled only a few cell types in the inner nuclear layer. Intracellular injection of Lucifer Yellow into these types showed them to be horizontal cells and cone bipolar cells. All stained bipolar cells ramified in sublamina a of the inner plexiform layer (IPL) and formed three classes. Two types ranged from 20 to 60 microns in diameter in both plexiform layers; the other large bipolar cell was 40-70 microns in diameter in the outer plexiform layer (OPL) and up to 150 microns in diameter in the IPL. The brightest type was narrowly stratified in the outer portion of sublamina a. Its density increased from about 500 cells/mm2 in the periphery to about 2,500 cells/mm2 in the visual streak. Staining of neighboring cells of this type showed that processes in the IPL rarely crossed, but often converged at a common site so as to impart a "honeycomb" appearance to a single sublayer of retina. The other small bipolar cell was similar in density and coverage, but stratified diffusely throughout sublamina a. The large bipolar cell stratified narrowly in the distal portion of sublamina a and was more sparsely distributed. Whether determined by staining adjacent cells or by density vs. area calculations, coverage in the OPL approached 1 for each type, as did coverage in the IPL for the two types with narrow fields.

Labeling and distribution of AII amacrine cells in the rabbit retina.

The fluorescent dye 4,6-diamino-2-phenylindole (DAPI) has previously been used to label starburst amacrine cells selectively in the rabbit retina and AII amacrine cells in the cat retina. Using the rabbit retina, we show that intraocular injection of DAPI labels starburst amacrine cells as seen 1-2 days later. In contrast, after a brief in vitro incubation with DAPI, AII amacrine cells are selectively labeled. Amacrine cells were identified by intracellular staining with Lucifer Yellow. AII amacrine cells are arranged in a regular mosaic with a density of 2,800 cells/mm2 near the visual streak declining to about 500 cells/mm2 in the far periphery. The coverage of the lobular dendritic field in sublamina alpha is approximately 1.5 across the retina, but the coverage of the fine dendritic field in sublamina b increases from 3 centrally to 4 in the inferior periphery, and to above 8 in the superior periphery.

A calbindin-immunoreactive cone bipolar cell type in the rabbit retina.

We have studied the distribution of the calcium-binding protein calbindin in the adult rabbit retina by using a commercially available antibody and immunocytochemical methods. The most heavily labeled cells are A-type horizontal cells, but B-type horizontal cells are also lightly labeled by this antibody. Among the horizontal cells, there is a mosaic of small, well-labeled somata, which we have identified as a subset of ON cone bipolar cells. In addition, some wide-field amacrine cells and a few large ganglion cells are also labeled for calbindin. The calbindin bipolar cells form a regular mosaic with a peak density of approximately 1,700 cells/mm2, falling to 550 cells/mm2 in the periphery. They account for about one-twelfth of cone bipolar cells, and they are narrowly stratified deep in sublamina 4 of the inner plexiform layer immediately above the rod bipolar terminals. Double-label experiments using an antibody to protein kinase C (PKC) indicate that the calbindin bipolar cells are completely distinct from the population of rod bipolar cells. Rod bipolar cells outnumber the calbindin cone bipolar cells by a factor of four to five. Further double-label experiments show that the calbindin bipolar cells are also labeled for recoverin. The calbindin bipolar cells are well coupled to AII amacrine cells, and they account for roughly 23% of the AII coupled bipolar cells. This suggests that there are three to four additional ON cone bipolar cell types that are coupled to AII amacrine cells. The calbindin cone bipolar cell described in this paper shares many characteristics with a reconstructed cone bipolar cell that forms the most gap junctions with AII amacrine cells (Strettoi et al. [1994] J. Comp. Neurol. 347:139-149). We conclude that these different methodologies provide complementary descriptions of the same cone bipolar cell type. The calbindin antibody defines a subset of cone bipolar cells in the rabbit retina. The cells in this subset are almost certainly the deepest of the cone bipolar cells. The tight stratification of the calbindin cone bipolar cell suggests that the inner plexiform layer is stratified according to depth, with narrow functional divisions within the broad partition of sublamina b, where ON signals are processed. The strength of coupling between the calbindin cone bipolar cells and AII amacrine cells suggests this pathway plays a major role under scotopic conditions.

Antibody to calretinin stains AII amacrine cells in the rabbit retina: double-label and confocal analyses.

The AII or rod amacrine cell is a critical interneuron in the rod pathway of mammalian retinae. In this report, it is shown that commercially available antibodies to the calcium binding protein calretinin may be used to label the population of AII amacrine cells selectively. Calretinin-positive amacrine cells had the morphological attributes of AII amacrine cells. Double-labeling procedures showed that calretinin-positive somata were surrounded by dopaminergic varicosities and that calretinin-positive dendrites enclosed rod bipolar terminals, both as previously described for AII amacrine cells. By analyzing the surrounding kernel for each labeled pixel in the rod bipolar image, it is shown here that AII processes are adjacent to rod bipolar terminals at a level that far exceeds the random overlap present in images in which one label was rotated out of phase. Such a spatial relationship is indicative of synaptic connections, as well described for rod bipolar input to AII amacrine cells. AII amacrine cells also were double-labeled for calretinin and parvalbumin; however, a scattergram analysis of red versus green intensity showed that the parvalbumin antibody stained additional unidentified amacrine cells. In conclusion, at the appropriate dilution, calretinin antibodies are a useful marker for AII amacrine cells in the rabbit retina.

AII amacrine cells limit scotopic acuity in central macaque retina: A confocal analysis of calretinin labeling.

We have used calretinin antibodies to label selectively the mosaic of AII amacrine cells in the macaque retina. Confocal analysis of double-labeled material indicated that AII dendrites spiral down around descending rod bipolar axons before enveloping the synaptic terminals. Processes from a previously observed dopaminergic plexus in the inner nuclear layer were observed to contact the somata of calretinin-positive AII somata. Intracellular neurobiotin injection revealed that AII amacrine cells are tracer coupled to other AII amacrine cells and to some unidentified cone bipolar cells. An analysis of the retinal distribution of macaque AII amacrine cells, including an area in and around the fovea, showed a peak density of approximately 5,000 cells/mm(2) at an eccentricity of 1.5 mm. Staining of AII amacrine cells in central retina with antibodies to calretinin was confirmed by confocal microscopy. These results indicate that calretinin antibodies can be used to label the AII amacrine cell population selectively and that primate AII amacrine cells share many of the features of previously described mammalian AII amacrine cells. The peak AII cell density closely matched the peak sampling rate of scotopic visual acuity. Calculations suggest that, in central macaque retina, where midget ganglion cells are more numerous, AII amacrine cells form the limit of scotopic visual acuity (Wässle et al. [1995] J. Comp. Neurol. 361:537-551). As the ganglion cell density falls rapidly away from the fovea, there is a cross-over point at around 15 degrees eccentricity that matches the inflection point in a psychophysically derived plot of scotopic visual acuity versus eccentricity (Lennie and Fairchild [1994] Vision Res. 34:477-482). The correspondence between the anatomic and psychophysical data supports our interpretation that the anatomic sampling rate of AII amacrine cells limits central scotopic acuity.

All indoleamine-accumulating cells in the rabbit retina contain GABA.

The indoleamine-accumulating amacrine cells of the rabbit retina are wide-field and numerous. They form a dense plexus in sublamina 5 of the inner plexiform layer where they make reciprocal synapses with rod bipolar cells. To provide a quantitative test for the colocalization of serotonin (5-HT) and gamma-aminobutyric acid (GABA) in the rabbit retina, we designed two parallel double-label experiments. In the first series, the indoleamine-accumulating cells were labeled with 5,7-dihydroxytryptamine (5,7-DHT), which was subsequently visualized by photooxidation in the presence of diaminobenzidine. This was combined with autoradiography for 3H-muscimol. In the second and complementary series, 3H-5-HT uptake was combined with postembedding GABA immunocytochemistry. These two experiments provided essentially identical results: over 98% of the indoleamine-accumulating amacrine cells were double-labeled. This means that, within the limit of experimental error, all the indoleamine-accumulating amacrine cells are GABAergic. The indoleamine-accumulating amacrine cells account for 15-20% of a large diverse group of GABA amacrine cells. In addition, the rare type 3 indoleamine-accumulating cells and fine processes running in the optic fiber layer were double-labeled. If there is insufficient 5-HT to support a transmitter role in the rabbit retina, our results suggest that the indoleamine-accumulating cells may use GABA as a neurotransmitter. Thus, rod bipolar cells, in common with other bipolar cell types, receive extensive negative feedback at GABA-mediated reciprocal synapses.

Coupling from AII amacrine cells to ON cone bipolar cells is bidirectional.

The AII amacrine cell is a critical interneuron in the rod pathway of the mammalian retina. Rod signals pass into cone pathways by means of gap junctions between AII amacrine cells and ON cone bipolar cells. Filling AII amacrine cells with Neurobiotin produces labeling of cone bipolar cells by means of these gap junctions. However, tracer injections into bipolar cells do not produce labeling of the AII network (Vaney [1997] Invest Ophthalmol Vis Sci. 38:267-273), which suggests that the AII/bipolar gap junctions allow the passage of tracer in only one direction. This mechanism stands in contrast to physiological results, which indicate that light adapted signals can pass from ON cone bipolar cells into the AII network (Xin and Bloomfield [1999] Vis Neurosci. 16:653-665). Here, we report that a variety of ON and OFF bipolar cells are sometimes anomalously coupled to the A-type horizontal cell network. These relatively rare examples do not result from dye injection errors, but seem to represent minor developmental errors. However, this provides a method to obtain Neurobiotin-filled cone bipolar cells without the necessity of impaling them with a microelectrode. Under these conditions, Neurobiotin spreads from ON cone bipolar cells into neighboring AII amacrine cells. The dye-coupled AII amacrine cells, positively identified by double labeling with an antibody against calretinin, were centered around anomalously coupled ON bipolar cells. These results indicate that AII/bipolar cell gap junctions allow tracer coupling in both directions, consistent with previous physiological results. The previous failure to detect the passage of neuronal tracer from injected bipolar cells to AII amacrine cells may reflect electrode damage or perhaps the asymmetrical voltage sensitivity of a heterotypic gap junction.

Rod pathways in the mammalian retina use connexin 36.

Many neurons in the mammalian retina are coupled by means of gap junctions. Here, we show that, in rabbit retina, an antibody to connexin 36 heavily labels processes of AII amacrine cells, a critical interneuron in the rod pathway. Image analysis indicates that Cx36 is primarily located at dendritic crossings between overlapping AII amacrine cells. This finding suggests that Cx36 participates in homotypic gap junctions between pairs of AII amacrine cells. Cx36 was also found at AII/cone bipolar contacts, previously shown to be gap junction sites. This finding suggests that Cx36 participates at gap junctions that may be heterotypic. These results place an identified neuronal connexin in the context of a well-defined retinal circuit. The absence of Cx36 in many other neurons known to be coupled suggests the presence of additional unidentified connexins in mammalian neurons. Conversely, Cx36 labeling in other regions of the retina is not associated with AII amacrine cells, indicating some other cell types use Cx36.

Design, synthesis, and pharmacological characterization of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740): a potent, selective, and orally active group 2 metabotropic glutamate receptor agonist possessing anticonvulsant and anxiolytic properties.

2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (9) was designed as a conformationally constrained analog of glutamic acid. For 9, the key torsion angles (tau 1 and tau 2) which determine the relative positions of the alpha-amino acid and distal carboxyl functionalities are constrained where tau 1 = 166.9 degrees or 202 degrees and tau 2 = 156 degrees, respectively. We hypothesized that 9 would closely approximate the proposed bioactive conformation of glutamate when acting at group 2 metabotropic glutamate receptors (mGluRs). The racemic target molecule (+/-)-9, its C2-diastereomer (+/-)-16, and its enantiomers (+)-9 (LY354740) and (-)-9 (LY366563) were prepared by an efficient, stereocontrolled, and high-yielding synthesis from 2-cyclopentenone. Our hypothesis that 9 could interact with high affinity and specificity at group 2 mGluRs has been supported by the observation that (+/-)-9 (EC50 = 0.086 +/- 0.025 microM) and its enantiomer (+)-9 (EC50 = 0.055 +/- 0.017 microM) are highly potent agonists for group 2 mGluRs in the rat cerebral cortical slice preparation (suppression of forskolin-stimulated cAMP formation) possessing no activity at other glutamate receptor sites (iGluR or group 1 mGluR) at concentrations up to 100 microM. Importantly, the mGluR agonist effects of (+)-9 are evident following oral administration in mice in both the elevated plus maze model of anxiety (ED50 = 0.5 mg/kg) and in the ACPD-induced limbic seizure model (ED50 = 45.6 mg/kg). Thus, (+)-9 is the first orally active group 2 mGluR agonist described thus far and is an important tool for studying the effects of compounds of this class in humans.

Synthesis, pharmacological characterization, and molecular modeling of heterobicyclic amino acids related to (+)-2-aminobicyclo[3.1.0] hexane-2,6-dicarboxylic acid (LY354740): identification of two new potent, selective, and systemically active agonists for group II metabotropic glutamate receptors.

As part of our ongoing research program aimed at the identification of highly potent, selective, and systemically active agonists for group II metabotropic glutamate (mGlu) receptors, we have prepared novel heterobicyclic amino acids (-)-2-oxa-4-aminobicyclo[3.1. 0]hexane-4,6-dicarboxylate (LY379268, (-)-9) and (-)-2-thia-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate (LY389795, (-)-10). Compounds (-)-9 and (-)-10 are structurally related to our previously described nanomolar potency group II mGlu receptor agonist, (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate (LY354740 monohydrate, 5), with the C4-methylene unit of 5 being replaced with either an oxygen atom (as in (-)-9) or a sulfur atom (as in (-)-10). Compounds (-)-9 and (-)-10 potently and stereospecifically displaced specific binding of the mGlu2/3 receptor antagonist ([3H]LY341495) in rat cerebral cortical homogenates, displaying IC50 values of 15 +/- 4 and 8.4 +/- 0.8 nM, respectively, while having no effect up to 100 000 nM on radioligand binding to the glutamate recognition site on NMDA, AMPA, or kainate receptors. Compounds (-)-9 and (-)-10 also potently displaced [3H]LY341495 binding from membranes expressing recombinant human group II mGlu receptor subtypes: (-)-9, Ki = 14.1 +/- 1.4 nM at mGlu2 and 5.8 +/- 0.64 nM at mGlu3; (-)-10, Ki = 40.6 +/- 3.7 nM at mGlu2 and 4.7 +/- 1.2 nM at mGlu3. Evaluation of the functional effects of (-)-9 and (-)-10 on second-messenger responses in nonneuronal cells expressing human mGlu receptor subtypes demonstrated each to be a highly potent agonist for group II mGlu receptors: (-)-9, EC50 = 2.69 +/- 0.26 nM at mGlu2 and 4.58 +/- 0.04 nM at mGlu3; (-)-10, EC50 = 3.91 +/- 0.81 nM at mGlu2 and 7.63 +/- 2. 08 nM at mGlu3. In contrast, neither compound (up to 10 000 nM) displayed either agonist or antagonist activity in cells expressing recombinant human mGlu1a, mGlu5a, mGlu4a, or mGlu7a receptors. The agonist effects of (-)-9 and (-)-10 at group II mGlu receptors were not totally specific, however, as mGlu6 agonist activity was observed at high nanomolar concentrations for (-)-9 (EC50 = 401 +/- 46 nM) and at micromolar concentrations (EC50 = 2 430 +/- 600 nM) for (-)-10; furthermore, each activated mGlu8 receptors at micromolar concentrations (EC50 = 1 690 +/- 130 and 7 340 +/- 2 720 nM, respectively). Intraperitoneal administration of either (-)-9 or (-)-10 in the mouse resulted in a dose-related blockade of limbic seizure activity produced by the nonselective group I/group II mGluR agonist (1S,3R)-ACPD ((-)-9 ED50 = 19 mg/kg, (-)-10 ED50 = 14 mg/kg), indicating that these molecules effectively cross the blood-brain barrier following systemic administration and suppress group I mGluR-mediated limbic excitation. Thus, heterobicyclic amino acids (-)-9 and (-)-10 are novel pharmacological tools useful for exploring the functions of mGlu receptors in vitro and in vivo.