Cortical high gamma network oscillations and connectivity: a translational index for antipsychotics to normalize aberrant neurophysiological activity.

Oscillatory activity in the gamma frequency range is a critical mechanism, which integrates neural networks within and across brain structures during cognitive processes. In schizophrenia, abnormalities in high gamma oscillations are ubiquitous and most likely reflect dysfunction in neuronal networks. In conscious rats, disturbed network oscillations associated with positive symptoms and cognitive deficits were modeled in different cortical areas by the dopaminergic agonist (amphetamine) and the N-methyl-D-aspartate (NMDA) receptor antagonists (PCP and MK801). Subsequently, the efficacies of marketed atypical antipsychotics (olanzapine, risperidone, and clozapine) to normalize dysfunctional oscillations and network connectivity were examined. Acute NMDA antagonists elicited aberrant synchrony in the gamma frequency oscillations. In addition, coherent slow alpha network activity was observed with MK801 and amphetamine, both of whose oscillatory rhythms were correlated with pronounced locomotor activity. All antipsychotics commonly decreased slow alpha and high gamma network oscillations in different cortical regions as well as motion behavior. In the combined treatments, antipsychotics attenuated NMDA antagonist-induced abnormalities in functional network oscillations and connectivity, whose effects on motor behavior is mechanistically related. These results suggest that pharmacologically induced disruption of cortical gamma oscillations and network connectivity in rats is a candidate model to study dysfunctional oscillatory patterns described in positive and negative symptoms of schizophrenia. The efficacy of antipsychotics to rescue cortical network oscillatory patterns is in line with the idea that glutamatergic and dopaminergic systems play a role in maintaining the integrity of cortical circuits. Thus, gamma oscillations could provide a powerful translational index to assess the integrity of neural networks and to evaluate the efficacy of drugs with potential antipsychotic properties.

Emergence of early alterations in network oscillations and functional connectivity in a tau seeding mouse model of Alzheimer's disease pathology.

Synaptic dysfunction and disconnectivity are core deficits in Alzheimer's disease (AD), preceding clear changes in histopathology and cognitive functioning. Here, the early and late effects of tau pathology induction on functional network connectivity were investigated in P301L mice. Multichannel EEG oscillations were used to compute (1) coherent activity between the prefrontal cortex (PFC) and hippocampus (HPC) CA1-CA3 networks; (2) phase-amplitude cross frequency coupling (PAC) between theta and gamma oscillations, which is instrumental in adequate cognitive functioning; (3) information processing as assessed by auditory evoked potentials and oscillations in the passive oddball mismatch negativity-like (MMN) paradigm. At the end, the density of tau aggregation and GABA parvalbumin (PV+) interneurons were quantified by immunohistochemistry. Early weakening of EEG theta oscillations and coherent activity were revealed between the PFC and HPC CA1 and drastic impairments in theta-gamma oscillations PAC from week 2 onwards, while PV+ interneurons count was not altered. Moreover, the tau pathology disrupted the MMN complex amplitude and evoked gamma oscillations to standard and deviant stimuli suggesting altered memory formation and recall. The induction of intracellular tau aggregation by tau seed injection results in early altered connectivity and strong theta-gamma oscillations uncoupling, which may be exploited as an early electrophysiological signature of dysfunctional neuronal networks.

Translational neurophysiological markers for activity of the metabotropic glutamate receptor (mGluR2) modulator JNJ-40411813: Sleep EEG correlates in rodents and healthy men.

Alterations in rapid eye movement sleep (REM) have been suggested as valid translational efficacy markers: activation of the metabotropic glutamate receptor 2 (mGluR2) was shown to increase REM latency and to decrease REM duration. The present paper addresses the effects on vigilance states of the mGluR2 positive allosteric modulator (PAM) JNJ-40411813 at different circadian times in rats and after afternoon dosing in humans. Due to its dual mGluR2 PAM/serotonin 2A (5-HT2A) receptor antagonism in rodents, mGlu2R specificity of effects was studied in wild-type (WT) and mGluR2 (-/-) mice. 5-HT2A receptor occupancy was determined in humans using positron emission tomography (PET). Tolerance development was examined in rats after chronic dosing. EEG oscillations and network connectivity were assessed using multi-channel EEG. In rats, JNJ-40411813 increased deep sleep time and latency of REM onset but reduced REM time when administered 2 h after 'lights on' (CT2): this was sustained after chronic dosing. At CT5 similar effects were elicited, at CT10 only deep sleep was enhanced. Withdrawal resulted in baseline values, while re-administration reinstated drug effects. Parieto-occipital cortical slow theta and gamma oscillations were correlated with low locomotion. The specificity of functional response was confirmed in WT but not mGluR2 (-/-) mice. A double-blind, placebo-controlled polysomnographic study in healthy, elderly subjects showed that 500 mg of JNJ-40411813 consistently increased deep sleep time, but had no effect on REM parameters. This deep sleep effect was not explained by 5-HT2A receptor binding, as in the PET study even 700 mg only marginally displaced the tracer. JNJ-40411813 elicited comparable functional responses in rodents and men if circadian time of dosing was taken into account. These findings underscore the translational potential of sleep mechanisms in evaluating mGluR2 therapeutics when administered at the appropriate circadian time.

Model-Based Once-Daily Darunavir/Ritonavir Dosing Recommendations in Pediatric HIV-1-Infected Patients Aged ≥3 to <12 Years.

An existing population pharmacokinetic model of darunavir in adults was updated using pediatric data from two studies evaluating weight-based, once-daily dosing of darunavir/ritonavir (ARIEL, NCT00919854 and DIONE, NCT00915655). The model was then used to provide once-daily dosing recommendations for darunavir/ritonavir in pediatric patients aged ≥3 to <12 years. The final model comprised two compartments with first-order absorption and apparent clearance dependent on the concentration of α1-acid glycoprotein. The recommended darunavir/ritonavir once-daily dosing regimens in children aged ≥3 to <12 years are: 35/7 mg/kg from 10 to <15 kg, 600/100 mg from 15 to <30 kg, 675/100 mg from 30 to <40 kg, and 800/100 mg for ≥40 kg. These doses should result in exposures similar to the adult exposure after treatment with darunavir/ritonavir 800/100 mg once daily, while minimizing pill burden and allowing a switch from suspension to tablet(s) as early as possible.

Subgroup analysis of virological response rates with once- and twice-daily darunavir/ritonavir in treatment-experienced patients without darunavir resistance-associated mutations in the ODIN trial.

BACKGROUND: ODIN (once-daily darunavir in treatment-experienced patients) was a 48-week, phase III, randomized, open-label trial comparing once-daily (qd) darunavir/ritonavir (DRV/r) 800/100 mg with twice-daily (bid) DRV/r 600/100 mg, both with an optimized background regimen [OBR; at least two nucleoside reverse transcriptase inhibitors (NRTIs)], in treatment-experienced, HIV-1-infected adults with no DRV resistance-associated mutations (RAMs) at screening. Week 48 analyses of virological response by subgroups are reported. METHODS: A total of 590 patients were randomized to receive qd (n=294) or bid (n=296) DRV/r. Virological response (HIV-1 RNA <50 copies/mL) was assessed according to: screening HIV-1 RNA (≥ or <50000 copies/mL), CD4 cell count, prior protease inhibitor (PI) use, number of active NRTIs in the OBR, presence of mutations (primary PI mutations, PI RAMs or M184V/I), gender, age, race, HIV-1 clade and adherence. RESULTS: Baseline characteristics were well balanced between arms and across subgroups. Response rates were comparable between qd and bid DRV/r treatments for all subgroups examined. Response rates were 78.4 and 76.8% in the qd and bid treatment arms, respectively, in patients with baseline HIV-1 RNA ≤ 50000 copies/mL and 52.8% in both arms in those with > 50000 copies/mL. Response rates for the qd and bid treatment arms by baseline CD4 cell count were also similar (69.6 vs. 65.2% for <200 cells/µL; 72.2 vs. 74.8% for 200- <350 cells/µL; 77.0 vs. 74.3% for ≥ 350 cells/µL). CONCLUSIONS: DRV/r administered either qd or bid provided effective treatment for antiretroviral treatment-experienced patients with no DRV RAMs, with comparable response rates across all subgroups studied. Low patient numbers in specific subgroups may limit interpretation of these specific subgroup results.

Effects of once-daily darunavir/ritonavir versus lopinavir/ritonavir on metabolic parameters in treatment-naive HIV-1-infected patients at week 96: ARTEMIS.

In the ARTEMIS trial, 689 treatment-naïve, HIV-1-infected adults received darunavir/ritonavir (DRV/r) 800/100 mg every day or lopinavir/ritonavir (LPV/r) 800/200 mg total daily dose plus fixed-dose tenofovir/emtricitabine. Week 96 metabolic parameters are reported. Adverse events (AEs) classed as metabolism/nutrition disorders were observed in 14% of DRV/r and 22% of LPV/r patients. Lipid-related AEs were reported in fewer DRV/r (8%) than LPV/r (16%) patients. A small increase in glucose and insulin levels was observed at week 96 in both groups. Lipoma was the only lipodystrophy-related AE reported in >1% of patients (DRV/r, n = 1; LPV/r, n = 4) and no grade 3 or 4 lipodystrophy-related AEs were reported. No clinically relevant changes from baseline were seen in anthropometric measurements in either group. Median mid-waist/hip ratio at week 96 was comparable to baseline in both arms. Over 96 weeks, DRV/r had a similar effect on glucose and insulin levels but a more favourable lipid profile than LPV/r in treatment-naïve, HIV-infected patients.

Final 192-week efficacy and safety of once-daily darunavir/ritonavir compared with lopinavir/ritonavir in HIV-1-infected treatment-naïve patients in the ARTEMIS trial.

OBJECTIVE: This paper presents the final analysis of once-daily darunavir/ritonavir (DRV/r) vs. lopinavir/ritonavir (LPV/r) in treatment-naïve HIV-1-infected adults. METHODS: ARTEMIS (AntiRetroviral Therapy with TMC114 ExaMined In naïve Subjects; NCT00258557) was a randomized, open-label, phase-III, 192-week trial. Patients were stratified by baseline HIV-1 RNA and CD4 count, and randomized to once-daily DRV/r 800/100 mg or LPV/r 800/200 mg total daily dose (either once or twice daily) plus tenofovir/emtricitabine. RESULTS: Of 689 randomized patients receiving treatment (DRV/r: 343; LPV/r: 346), 85 and 114 patients in the DRV/r and LPV/r arms, respectively, had discontinued by week 192. Noninferiority was shown in the primary endpoint of virological response (HIV-1 RNA < 50 copies/mL) [DRV/r: 68.8%; LPV/r: 57.2%; P < 0.001; intent to treat (ITT)/time to loss of virological response; estimated difference in response 11.6% (95% confidence interval 4.4-18.8%)]. Statistical superiority in virological response of DRV/r over LPV/r was demonstrated for the primary endpoint (P = 0.002) and for the ITT non-virological-failure-censored analysis (87.4% vs. 80.8%, respectively; P = 0.040). No protease inhibitor (PI) primary mutations developed and only low levels of nucleoside reverse transcriptase inhibitor (NRTI) resistance developed in virological failures in both groups. Significantly fewer discontinuations because of adverse events were observed with DRV/r (4.7%) than with LPV/r (12.7%; P = 0.005). Grade 2-4 treatment-related diarrhoea was significantly less frequent with DRV/r than with LPV/r (5.0% vs. 11.3%, respectively; P = 0.003). DRV/r was associated with smaller median increases in total cholesterol and triglyceride levels than LPV/r. Changes in low- and high-density lipoprotein cholesterol were similar between groups. Similar increases in aspartate aminotransferase and alanine aminotransferase for DRV/r and LPV/r were observed. CONCLUSION: Over 192 weeks, once-daily DRV/r was noninferior and statistically superior in virological response to LPV/r, with a more favourable gastrointestinal profile, demonstrating its suitability for long-term use in treatment-naïve patients.

Antiviral and lung protective activity of a novel respiratory syncytial virus fusion inhibitor in a mouse model.

Respiratory syncytial virus (RSV) causes bronchiolitis in young children and common colds in adults. There is no licensed vaccine, and prophylactic treatment with palivizumab is very expensive and limited to high-risk infants. Ribavirin is used as an antiviral treatment in infants and immunosuppressed patients, and its use is limited due to side-effects, toxicity to the recipient and staff, and evidence of marginal clinical efficacy. Therefore, we studied the in vivo kinetics, and the antiviral and protective properties of a novel candidate for RSV disease treatment. The drug is a small molecule (TMC353121) discovered by screening for fusion inhibitory properties against RSV in a cellular infection model. The pharmacokinetics of TMC353121 was studied in BALB/c mice and antiviral effects determined by testing viral loads in lung tissue by quantitative RT-PCR and plaque assay after intranasal RSV infection. At doses of 0.25-10 mg · kg(-1), TMC353121 significantly reduced viral load, bronchoalveolar lavage cell accumulation and the severity of lung histopathological change after infection. Treatment remained effective if started within 48 h of infection, but was ineffective thereafter. Therefore, TMC353121 is a novel potent antiviral drug, in vivo reducing RSV replication and inhibiting consequential lung inflammation, with a great potential for further clinical development.

Natal dispersal and parental escorting predict relatedness between mates in a passerine bird.

Although relatedness between mates is of considerable evolutionary and ecological significance, the way in which the level of relatedness is determined by different behavioural processes remains largely unknown. We investigated the role of behaviour in predicting mate relatedness in great tits using genotypic markers and detailed observations. We studied how mate relatedness is influenced by natal dispersal, inbreeding/outbreeding avoidance after natal dispersal and a behaviour not previously considered that influences membership to social aggregations, namely family escorting behaviour by parents. Among locally born individuals, the level of mate relatedness decreased with natal dispersal distance for females, but not for males. In contrast, mate relatedness was negatively related to the extent of family movements for males, but not for females. However, family movements did not predict dispersal distance for either sex. Local recruits were more related to their mates than immigrants, but this was only significant for females. No evidence was found for inbreeding/outbreeding avoidance after dispersal. Our results suggest that, in highly mobile species, mating options are spatially and/or socially limited, and that parents influence mating options of their offspring before dispersal.

Do sibling tits (Parus major, P. caeruleus) disperse over similar distances and in similar directions?

We studied dispersal movements by sibling pairs of great tits, Parus major, and blue tits, P. caeruleus, in a patchy environment, in order to test whether siblings are more similar in dispersal than expected by chance. Because of possible common environmental effects due to the heterogeneity and finiteness of the study area, we compared the similarity among siblings with the similarity between each sibling and an unrelated bird that fledged in the same patch and year, as close to the siblings' nest as possible. Siblings of both species were not more similar in dispersal distance than they were to control birds. However, great tit siblings dispersed in similar directions compared to control birds, and this result was not affected by the degree of matching between sibling and control birds. As a consequence, siblings ended up breeding at closer distances from one another than control birds. Heritability values calculated from parent-offspring regressions were close to zero, suggesting that there is no additive genetic variance for dispersal distance or dispersal direction. We propose that similarity in dispersal direction originates from association of siblings during dispersal or during activities that influence the choice of direction, such as postfledging family movements. Our results show that non-independence in the choice of dispersal direction by siblings may influence small-scale kin structure in this population with high local recruitment.

A strong association between immune responsiveness and natal dispersal in a songbird.

Because parasite faunas typically show considerable spatio-temporal variation, and because parasites can have important fitness consequences, host defence mechanisms, including the immune system, can be expected to coevolve with natal dispersal, i.e. the movement of a newborn individual from its site of birth to its first site of reproduction. We demonstrate that immigrant individuals show a significantly higher humoral immune response towards a novel antigen than do local recruits in two independent populations of the great tit (Parus major). There was no effect of age, sex, tarsus length or body mass on immune responsiveness. Our results are consistent with the idea that phenotype-dependent dispersal and/or dispersal-by-phenotype-dependent selection establish a relation between immune responsiveness and natal dispersal.

A comparison of microsatellite-based pairwise relatedness estimators.

Studies of inbreeding depression or kin selection require knowledge of relatedness between individuals. If pedigree information is lacking, one has to rely on genotypic information to infer relatedness. In this study we investigated the performance (absolute and relative) of 10 marker-based relatedness estimators using allele frequencies at microsatellite loci obtained from natural populations of two bird species and one mammal species. Using Monte Carlo simulations we show that many factors affect the performance of estimators and that different sets of loci promote the use of different estimators: in general, there is no single best-performing estimator. The use of locus-specific weights turns out to greatly improve the performance of estimators when marker loci are used that differ strongly in allele frequency distribution. Microsatellite-based estimates are expected to explain between 25 and 79% of variation in true relatedness depending on the microsatellite dataset and on the population composition (i.e. the frequency distribution of relationship in the population). We recommend performing Monte Carlo simulations to decide which estimator to use in studies of pairwise relatedness.