GABA-B receptor function in healthy volunteers, a pharmacokinetic and pharmacodynamic study of two doses of baclofen compared to placebo

AIMS AND HYPOTHESIS To assess the subjective and objective effects of baclofen on brain function in healthy volunteers. BACKGROUND Recent evidence suggests baclofen, a γ-aminobutyric acid type B (GABA-B) receptor agonist, reduces alcohol consumption and craving and promotes abstinence in alcoholics. However, characterisation of the GABA-B receptor system in clinical addiction is limited, and it is unclear why some patients require, or tolerate, higher doses to treat alcoholism. This study assesses the effects of baclofen on brain function in healthy volunteers to inform future studies investigating the sensitivity of GABA-B receptors in alcohol addiction. METHODS Eight healthy male volunteers completed a double blind randomised 3-way cross over study, receiving oral placebo (vitamin C 100mg), 10mg and 60mg baclofen. Subjective and objective measurements were taken at baseline (before medication) and at +30mins, 1, 2, 3, 4 and 6 hours after dosing. Objective measures included blood plasma samples, heart rate and blood pressure. Subjective measures included; the Subjective High Assessment Questionnaire (SHAS), visual analogue scales for sleepy, relaxed, tense and alert and a motor coordination task (zig-zag task). Pharmacokinetic data was obtained using liquid chromatography mass-spectrometry (LC-MS) to measure plasma baclofen concentrations. RESULTS 60mg Baclofen showed changes in subjective measures peaking at 2 hours post dosing compared with placebo, including a significant increase (p<0.05) in total SHAS scores with individual items, including feeling ‘drunk or intoxicated’, effects of alcohol and ‘muddled or confused’ particular affected.. Systolic blood pressure was significantly increased (p<0.05) at the 2 hours post 60mg dose. For both 10mg and 60mg baclofen, peak plasma concentration was achieved 60 minutes post dose. Pharmacokinetic data will be presented. There were no significant changes in these measures between 10mg Baclofen and placebo. CONCLUSIONS The objective and subjective measures used in this study are able to differentiate between placebo and 60mg baclofen. These findings will inform further research investigating the sensitivity of GABA-B receptors in alcohol addiction

An Early Look at a Time-Lapse 3D VSP

In 2007 Australian Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) started a project to evaluate the available technology for monitoring the movement of CO2 in an underground reservoir. In stage one of this project CO2 and methane are being produced in a nearby well, then the CO2/CH4 is being injected back down a second well into a depleted gas sand. The movement of the CO2 up-dip needs to be remotely monitored. One of the technologies being evaluated to monitor the movement of the CO2 is 3D VSP. The CRC-1 injector well is instrumented with 10 3C downhole accelerometers. A baseline 3D VSP survey was shot around this well in late 2007 and was followed by a repeat survey in 2010. We hope to monitor the movement of CO2 around the CRC-1 well by observing changes in the time-lapse signature

M-CSF instructs myeloid lineage fate in single haematopoietic stem cells

Under stress conditions such as infection or inflammation the body rapidly needs to generate new blood cells that are adapted to the challenge. Haematopoietic cytokines are known to increase output of specific mature cells by affecting survival, expansion and differentiation of lineage-committed progenitors, but it has been debated whether long-term haematopoietic stem cells (HSCs) are susceptible to direct lineage-specifying effects of cytokines. Although genetic changes in transcription factor balance can sensitize HSCs to cytokine instruction, the initiation of HSC commitment is generally thought to be triggered by stochastic fluctuation in cell-intrinsic regulators such as lineage-specific transcription factors, leaving cytokines to ensure survival and proliferation of the progeny cells. Here we show that macrophage colony-stimulating factor (M-CSF, also called CSF1), a myeloid cytokine released during infection and inflammation, can directly induce the myeloid master regulator PU.1 and instruct myeloid cell-fate change in mouse HSCs, independently of selective survival or proliferation. Video imaging and single-cell gene expression analysis revealed that stimulation of highly purified HSCs with M-CSF in culture resulted in activation of the PU.1 promoter and an increased number of PU.1(+) cells with myeloid gene signature and differentiation potential. In vivo, high systemic levels of M-CSF directly stimulated M-CSF-receptor-dependent activation of endogenous PU.1 protein in single HSCs and induced a PU.1-dependent myeloid differentiation preference. Our data demonstrate that lineage-specific cytokines can act directly on HSCs in vitro and in vivo to instruct a change of cell identity. This fundamentally changes the current view of how HSCs respond to environmental challenge and implicates stress-induced cytokines as direct instructors of HSC fate

Using baclofen to explore GABA-B receptor function in alcohol dependence: insights from pharmacokinetic and pharmacodynamic measures

Background: The role of GABA-B neurotransmission in addiction has recently received increased attention, with clinical trials indicating that baclofen, a GABA-B receptor agonist, may reduce alcohol consumption, craving and promote abstinence. However, the optimal dose to treat alcohol dependence is unclear with patients requesting and tolerating much higher doses of baclofen, compared with other clinical uses. We assessed the pharmacokinetics and pharmacodynamics (PK/PD) of baclofen to provide insight into GABA-B sensitivity in this patient group, relative to controls. Methods: Male healthy volunteers (controls, n = 12) and abstinent alcohol dependent individuals (AD, n = 8) received single oral doses of baclofen or placebo in a 3-way crossover design. Controls received placebo/10 mg/60 mg baclofen in a randomized, double-blind design, AD received placebo/60 mg/90 mg baclofen in a single-blind design. PK/PD measures were recorded at baseline and multiple time-points up to 6 h post-dosing, including plasma baclofen, plasma growth hormone (GH), Subjective High Assessment Scale (SHAS) and biphasic alcohol effects scale (BAES). Repeated measures ANOVA analysis explored “change from baseline” dose, time, group, and interaction effects, t-tests compared peak effects. Results: Dose-dependent effects of baclofen on PK and PD measures were observed in both control and AD groups. Whilst there were no significant group differences in any baclofen PK parameters (t1/2, tmax, Cmax, AUC), marked differences in PD effects were clearly evident. In controls, 60 mg baclofen significantly increased total SHAS and BAES scores, and significantly increased plasma GH levels compared with placebo, with peak effects at 60–120 min, in line with its PK profile. In AD, 60 mg baclofen had limited effects on these parameters; SHAS scores, BAES scores and plasma GH levels were significantly blunted compared with controls (significant group*time interactions P = 0.0014, 0.0015 and P < 0.0001, respectively). Conclusions: Our study shows blunted sensitivity to baclofen in AD relative to controls, with no difference in PK suggesting a lower GABA-B receptor sensitivity. This may explain why higher baclofen doses are requested and tolerated in the treatment of alcohol dependence. Our data has implications for choice of dose in future clinical trials in AD and possibly other substances of dependence

Bayesian hierarchical clustering for studying cancer gene expression data with unknown statistics

Clustering analysis is an important tool in studying gene expression data. The Bayesian hierarchical clustering (BHC) algorithm can automatically infer the number of clusters and uses Bayesian model selection to improve clustering quality. In this paper, we present an extension of the BHC algorithm. Our Gaussian BHC (GBHC) algorithm represents data as a mixture of Gaussian distributions. It uses normal-gamma distribution as a conjugate prior on the mean and precision of each of the Gaussian components. We tested GBHC over 11 cancer and 3 synthetic datasets. The results on cancer datasets show that in sample clustering, GBHC on average produces a clustering partition that is more concordant with the ground truth than those obtained from other commonly used algorithms. Furthermore, GBHC frequently infers the number of clusters that is often close to the ground truth. In gene clustering, GBHC also produces a clustering partition that is more biologically plausible than several other state-of-the-art methods. This suggests GBHC as an alternative tool for studying gene expression data. The implementation of GBHC is available at https://sites. google.com/site/gaussianbhc

Apaf-1 and caspase-9 do not act as tumor suppressors in myc-induced lymphomagenesis or mouse embryo fibroblast transformation

Based on experiments with cultured fibroblasts, the apoptosis regulators caspase-9 and Apaf-1 are hypothesized to function as tumor suppressors. To investigate their in vivo role in lymphomagenesis, an IgH enhancer-driven c-myc transgene was crossed onto Apaf-1−/− and caspase-9−/− mice. Due to perinatal lethality, Eμ-myc transgenic Apaf-1−/− or caspase-9−/− fetal liver cells were used to reconstitute lethally irradiated recipient mice. Surprisingly, no differences were seen in rate, incidence, or severity of lymphoma with loss of Apaf-1 or caspase-9, and Apaf-1 was not a critical determinant of anticancer drug sensitivity of c-myc–induced lymphomas. Moreover, loss of Apaf-1 did not promote oncogene-induced transformation of mouse embryo fibroblasts. Thus, Apaf-1 and caspase-9 do not suppress c-myc–induced lymphomagenesis and embryo fibroblast transformation

Cerebral blood flow predicts differential neurotransmitter activity

Application of metabolic magnetic resonance imaging measures such as cerebral blood flow in translational medicine is limited by the unknown link of observed alterations to specific neurophysiological processes. In particular, the sensitivity of cerebral blood flow to activity changes in specific neurotransmitter systems remains unclear. We address this question by probing cerebral blood flow in healthy volunteers using seven established drugs with known dopaminergic, serotonergic, glutamatergic and GABAergic mechanisms of action. We use a novel framework aimed at disentangling the observed effects to contribution from underlying neurotransmitter systems. We find for all evaluated compounds a reliable spatial link of respective cerebral blood flow changes with underlying neurotransmitter receptor densities corresponding to their primary mechanisms of action. The strength of these associations with receptor density is mediated by respective drug affinities. These findings suggest that cerebral blood flow is a sensitive brain-wide in-vivo assay of metabolic demands across a variety of neurotransmitter systems in humans

Genetic diversity affects seedling survival but not growth or seed germination in the Bornean endemic dipterocarp Parashorea tomentella

Background: Logging and habitat fragmentation of tropical rain forests may disrupt patterns of gene flow and genetic diversity. Consequently, inbreeding in tree populations may reduce fitness and increase extinction risks, especially among species that are predominantly outcrossing, dependent on biotic pollination and/or display limited seed dispersal such as species of the Dipterocarpaceae. Aims: To test the hypothesis that heterozygosity of individual progeny affects their likelihood of germination and the growth and survival of seedlings. Methods: Standardised measure of multilocus heterozygosity (sMLH) was estimated from seven microsatellite loci for individual progeny collected from 18 mother trees of the large dipterocarp Parashorea tomentella. The relationships among sMLH, germination and seedling growth and survival were determined for the progeny. Results: Seedling survival over 18 months increased with greater sMLH and fresh fruit weight. This result was expressed under all experimentally controlled combinations of light and nutrient availability in the nursery and in the shaded understorey of primary forest where survival overall was much lower than in the nursery. sMLH did not affect the probability of germination or seedling growth rate in any experimental treatment. Conclusions: These results provide evidence that reduced heterozygosity is associated with reduced seedling survival in a tropical forest tree species

Defining Substance Use Disorders: Do We Really Need More Than Heavy Use?

Aims: The aim of the study was to explore whether the concept of heavy substance use over time can be used as definition of substance use disorder. Methods: Narrative review. Results: Heavy use over time clearly underlies the neurobiological changes associated with current thinking of substance use disorders. In addition, there is evidence that heavy use over time can explain the majority of social problems and of burden of disease (morbidity and mortality). A definition of substance use disorders via heavy use over time would avoid some of the problems of current conceptualizations, for instance the cultural specificity of concepts such as loss of control. Finally, stressing the continuum of use may avoid the high level of stigmatization currently associated with substance use disorders. Conclusion: ‘Heavy substance use over time' seems to be a definition of substance use disorders in line with results of basic research and epidemiology. Additionally, it reduces stigmatization. This approach should thus be further explore

Pax5 loss imposes a reversible differentiation block in B-progenitor acute lymphoblastic leukemia

Loss-of-function mutations in hematopoietic transcription factors including PAX5 occur in most cases of B-progenitor acute lymphoblastic leukemia (B-ALL), a disease characterized by the accumulation of undifferentiated lymphoblasts. Although PAX5 mutation is a critical driver of B-ALL development in mice and humans, it remains unclear how its loss contributes to leukemogenesis and whether ongoing PAX5 deficiency is required for B-ALL maintenance. Here we used transgenic RNAi to reversibly suppress endogenous Pax5 expression in the hematopoietic compartment of mice, which cooperates with activated signal transducer and activator of transcription 5 (STAT5) to induce B-ALL. In this model, restoring endogenous Pax5 expression in established B-ALL triggers immunophenotypic maturation and durable disease remission by engaging a transcriptional program reminiscent of normal B-cell differentiation. Notably, even brief Pax5 restoration in B-ALL cells causes rapid cell cycle exit and disables their leukemia-initiating capacity. These and similar findings in human B-ALL cell lines establish that Pax5 hypomorphism promotes B-ALL self-renewal by impairing a differentiation program that can be re-engaged despite the presence of additional oncogenic lesions. Our results establish a causal relationship between the hallmark genetic and phenotypic features of B-ALL and suggest that engaging the latent differentiation potential of B-ALL cells may provide new therapeutic entry points.Grace J. Liu, Luisa Cimmino, Julian G. Jude, Yifang Hu, Matthew T. Witkowski, Mark D. McKenzie, Mutlu Kartal-Kaess, Sarah A. Best, Laura Tuohey, Yang Liao, Wei Shi, Charles G. Mullighan, Michael A. Farrar, Stephen L. Nutt, Gordon K. Smyth, Johannes Zuber, and Ross A. Dickin