Parvalbumin and Somatostatin Interneurons Contribute to the Generation of Hippocampal Gamma Oscillations.

γ-frequency oscillations (30-120 Hz) in cortical networks influence neuronal encoding and information transfer, and are disrupted in multiple brain disorders. While synaptic inhibition is important for synchronization across the γ-frequency range, the role of distinct interneuronal subtypes in slow (<60 Hz) and fast γ states remains unclear. Here, we used optogenetics to examine the involvement of parvalbumin-expressing (PV+) and somatostatin-expressing (SST+) interneurons in γ oscillations in the mouse hippocampal CA3 ex vivo, using animals of either sex. Disrupting either PV+ or SST+ interneuron activity, via either photoinhibition or photoexcitation, led to a decrease in the power of cholinergically induced slow γ oscillations. Furthermore, photoexcitation of SST+ interneurons induced fast γ oscillations, which depended on both synaptic excitation and inhibition. Our findings support a critical role for both PV+ and SST+ interneurons in slow hippocampal γ oscillations, and further suggest that intense activation of SST+ interneurons can enable the CA3 circuit to generate fast γ oscillations.SIGNIFICANCE STATEMENT The generation of hippocampal γ oscillations depends on synchronized inhibition provided by GABAergic interneurons. Parvalbumin-expressing (PV+) interneurons are thought to play the key role in coordinating the spike timing of excitatory pyramidal neurons, but the role distinct inhibitory circuits in network synchronization remains unresolved. Here, we show, for the first time, that causal disruption of either PV+ or somatostatin-expressing (SST+) interneuron activity impairs the generation of slow γ oscillations in the ventral hippocampus ex vivo We further show that SST+ interneuron activation along with general network excitation is sufficient to generate high-frequency γ oscillations in the same preparation. These results affirm a crucial role for both PV+ and SST+ interneurons in hippocampal γ oscillation generation.

A brain-wide functional map of the serotonergic responses to acute stress and fluoxetine.

Central serotonin (5-HT) orchestrates myriad cognitive processes and lies at the core of many stress-related psychiatric illnesses. However, the basic relationship between its brain-wide axonal projections and functional dynamics is not known. Here we combine optogenetics and fMRI to produce a brain-wide 5-HT evoked functional map. We find that DRN photostimulation leads to an increase in the hemodynamic response in the DRN itself, while projection areas predominately exhibit a reduction of cerebral blood volume mirrored by suppression of cortical delta oscillations. We find that the regional distribution of post-synaptically expressed 5-HT receptors better correlates with DRN 5-HT functional connectivity than anatomical projections. Our work suggests that neuroarchitecture is not the primary determinant of function for the DRN 5-HT. With respect to two 5-HT elevating stimuli, we find that acute stress leads to circuit-wide blunting of the DRN output, while the SSRI fluoxetine noticeably enhances DRN functional connectivity. These data provide fundamental insight into the brain-wide functional dynamics of the 5-HT projection system.

NMDA-receptor antibodies alter cortical microcircuit dynamics.

NMDA-receptor antibodies (NMDAR-Abs) cause an autoimmune encephalitis with a diverse range of EEG abnormalities. NMDAR-Abs are believed to disrupt receptor function, but how blocking this excitatory synaptic receptor can lead to paroxysmal EEG abnormalities-or even seizures-is poorly understood. Here we show that NMDAR-Abs change intrinsic cortical connections and neuronal population dynamics to alter the spectral composition of spontaneous EEG activity and predispose brain dynamics to paroxysmal abnormalities. Based on local field potential recordings in a mouse model, we first validate a dynamic causal model of NMDAR-Ab effects on cortical microcircuitry. Using this model, we then identify the key synaptic parameters that best explain EEG paroxysms in pediatric patients with NMDAR-Ab encephalitis. Finally, we use the mouse model to show that NMDAR-Ab-related changes render microcircuitry critically susceptible to overt EEG paroxysms when these key parameters are changed, even though the same parameter fluctuations are tolerated in the in silico model of the control condition. These findings offer mechanistic insights into circuit-level dysfunction induced by NMDAR-Ab.

THM and HAA formation from NOM in raw and treated surface waters.

The disinfection by-product (DBP) formation potential (FP) of natural organic matter (NOM) in surface water sources has been studied with reference to the key water quality determinants (WQDs) of UV absorption (UV254), colour, and dissolved organic carbon (DOC) concentration. The data set used encompassed raw and treated water sampled over a 30-month period from 30 water treatment works (WTWs) across Scotland, all employing conventional clarification. Both trihalomethane (THM) and haloacetic acid (HAA) FPs were considered. In addition to the standard bulk WQDs, the DOC content was fractionated and analysed for the hydrophobic (HPO) and hydrophilic (HPI) fractions. Results were quantified in terms of the yield (dDBPFP/dWQD) and the linear regression coefficient R2 of the yield trend. The NOM in the raw waters was found to comprise 30-84% (average 66%) of the more reactive HPO material, with this proportion falling to 18-63% (average 50%) in the treated water. Results suggested UV254 to be as good an indicator of DBPFP as DOC or HPO for the raw waters, with R2 values ranging from 0.79 to 0.82 for THMs and from 0.71 to 0.73 for HAAs for these three determinants. For treated waters the corresponding values were significantly lower at 0.52-0.67 and 0.46-0.47 respectively, reflecting the lower HPO concentration and thus UV254 absorption and commensurately reduced precision due to the limit of detection of the analytical instrument. It is concluded that fractionation offers little benefit in attempting to discern or predict chlorinated carbonaceous DBP yield for the waters across the geographical region studied. UV254 offered an adequate estimate of DBPFP based on a mean yield of ∼2600 and ∼2800 µg per cm-1 absorbance for THMFP for the raw and treated waters respectively and ∼3800 and2900 µg cm-1 for HAAFP, albeit with reduced precision for the treated waters.

Epileptogenic effects of NMDAR antibodies in a passive transfer mouse model.

Most patients with N-methyl D-aspartate-receptor antibody encephalitis develop seizures but the epileptogenicity of the antibodies has not been investigated in vivo. Wireless electroencephalogram transmitters were implanted into 23 C57BL/6 mice before left lateral ventricle injection of antibody-positive (test) or healthy (control) immunoglobulin G. Mice were challenged 48 h later with a subthreshold dose (40 mg/kg) of the chemo-convulsant pentylenetetrazol and events recorded over 1 h. Seizures were assessed by video observation of each animal and the electroencephalogram by an automated seizure detection programme. No spontaneous seizures were seen with the antibody injections. However, after the pro-convulsant, the test mice (n = 9) had increased numbers of observed convulsive seizures (P = 0.004), a higher total seizure score (P = 0.003), and a higher number of epileptic 'spike' events (P = 0.023) than the control mice (n = 6). At post-mortem, surprisingly, the total number of N-methyl D-aspartate receptors did not differ between test and control mice, but in test mice the levels of immunoglobulin G bound to the left hippocampus were higher (P < 0.0001) and the level of bound immunoglobulin G correlated with the seizure scores (R(2) = 0.8, P = 0.04, n = 5). Our findings demonstrate the epileptogenicity of N-methyl D-aspartate receptor antibodies in vivo, and suggest that binding of immunoglobulin G either reduced synaptic localization of N-methyl D-aspartate receptors, or had a direct effect on receptor function, which could be responsible for seizure susceptibility in this acute short-term model.

In vitro and in vivo activities of the nitroimidazole TBA-354 against Mycobacterium tuberculosis.

Nitroimidazoles are a promising new class of antitubercular agents. The nitroimidazo-oxazole delamanid (OPC-67683, Deltyba) is in phase III trials for the treatment of multidrug-resistant tuberculosis, while the nitroimidazo-oxazine PA-824 is entering phase III for drug-sensitive and drug-resistant tuberculosis. TBA-354 (SN31354[(S)-2-nitro-6-((6-(4-trifluoromethoxy)phenyl)pyridine-3-yl)methoxy)-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine]) is a pyridine-containing biaryl compound with exceptional efficacy against chronic murine tuberculosis and favorable bioavailability in preliminary rodent studies. It was selected as a potential next-generation antituberculosis nitroimidazole following an extensive medicinal chemistry effort. Here, we further evaluate the pharmacokinetic properties and activity of TBA-354 against Mycobacterium tuberculosis. TBA-354 is narrow spectrum and bactericidal in vitro against replicating and nonreplicating Mycobacterium tuberculosis, with potency similar to that of delamanid and greater than that of PA-824. The addition of serum protein or albumin does not significantly alter this activity. TBA-354 maintains activity against Mycobacterium tuberculosis H37Rv isogenic monoresistant strains and clinical drug-sensitive and drug-resistant isolates. Spontaneous resistant mutants appear at a frequency of 3 × 10(-7). In vitro studies and in vivo studies in mice confirm that TBA-354 has high bioavailability and a long elimination half-life. In vitro studies suggest a low risk of drug-drug interactions. Low-dose aerosol infection models of acute and chronic murine tuberculosis reveal time- and dose-dependent in vivo bactericidal activity that is at least as potent as that of delamanid and more potent than that of PA-824. Its superior potency and pharmacokinetic profile that predicts suitability for once-daily oral dosing suggest that TBA-354 be studied further for its potential as a next-generation nitroimidazole.

Epidemiology, disease burden and outcomes of cirrhosis in a large secondary care hospital in South Auckland, New Zealand.

BACKGROUND: Liver cirrhosis is an important cause of morbidity and mortality; however, little is known about its impact in New Zealand. AIMS: We aim to determine the disease burden, epidemiology and outcomes of cirrhotic patients. METHODS: This is a retrospective study of cirrhosis patients under secondary public hospital care in a geographically defined region, between the years 2000 and 2011. Cirrhosis complications and mortality was recorded. Poisson log-linear regression analysis was performed for incidence rate ratio (IRR) and Cox regression analysis was used to analyse time-related events. RESULTS: Seven hundred and forty-six cirrhotic patients were analysed; most were European/Other (39.9%), Pacific islanders (21.6%), Southeast Asian/Chinese (17.8%) and Maori (12.3%). 68.4% were male. The common primary aetiologies for cirrhosis were chronic hepatitis B (CHB) cirrhosis (37.3%), alcoholic liver disease (ALD) cirrhosis (24.1%), chronic hepatitis C (CHC) cirrhosis (22.3%) and non-alcoholic fatty liver disease (NAFLD) cirrhosis (16.4%). The hepatocellular carcinoma (HCC) mortality rates were highest in NAFLD and CHB cirrhosis groups (3.0 and 3.1 per 100 patient-year respectively), compared with ALD and CHC groups (2.2 and 1.4 per 100 patient-year, all P < 0.05 respectively). Patients with ALD and NAFLD cirrhosis had the highest all-cause and non-HCC mortality rate compared with viral hepatitis cirrhosis groups. The IRR for HCC incidence, liver-related mortality and HCC mortality were 1.087, 1.098 and 1.114, respectively (all P < 0.001), suggesting increasing incidence and disease burden over the study period. CONCLUSION: The number of cirrhotic patients in secondary care is increasing steadily. Cirrhosis complications and mortality rates are also rising, particularly the incidence and mortality of HCC.

Presynaptic self-depression at developing neocortical synapses.

A central tenet of most theories of synaptic modification during cortical development is that correlated activity drives plasticity in synaptically connected neurons. Unexpectedly, however, using sensory-evoked activity patterns recorded from the developing mouse cortex in vivo, the synaptic learning rule that we uncover here relies solely on the presynaptic neuron. A burst of three presynaptic spikes followed, within a restricted time window, by a single presynaptic spike induces robust long-term depression (LTD) at developing layer 4 to layer 2/3 synapses. This presynaptic spike pattern-dependent LTD (p-LTD) can be induced by individual presynaptic layer 4 cells, requires presynaptic NMDA receptors and calcineurin, and is expressed presynaptically. However, in contrast to spike timing-dependent LTD, p-LTD is independent of postsynaptic and astroglial signaling. This spike pattern-dependent learning rule complements timing-based rules and is likely to play a role in the pruning of synaptic input during cortical development.

In vitro and in vivo activity of clofazimine against Mycobacterium tuberculosis persisters.

OBJECTIVE: To assess the activity of clofazimine (CFZ) against Mycobacterium tuberculosis persisters using an oxygen depletion model and a low-dose aerosol mouse model of chronic tuberculosis (TB). DESIGN: In in vitro experiments, CFZ showed much better activity than isoniazid under anaerobic conditions. In a low-dose aerosol mouse model of TB, we evaluated the efficacy of CFZ and moxifloxacin at different doses following treatment durations of 30, 60 and 90 days. RESULTS: CFZ showed significant bactericidal activity in the mouse model over the wide dose range of 2-200 mg/kg. CFZ activity was dose-dependent. The bacilli were eradicated in the CFZ 200 mg/kg group after treatment for 60 days, and in the CFZ 20 mg/kg group after 90 days of treatment. CONCLUSION: CFZ exhibits dose-dependent, sustained bactericidal activity against M. tuberculosis persisters, and thus warrants further study to demonstrate its potential to contribute significantly in a novel treatment-shortening regimen.

Close temporal coupling of neuronal activity and tissue oxygen responses in rodent whisker barrel cortex.

Neuronal activity elicits metabolic and vascular responses, during which oxygen is first consumed and then supplied to the tissue via an increase in cerebral blood flow. Understanding the spatial and temporal dynamics of blood and tissue oxygen (To2) responses following neuronal activity is crucial for understanding the physiological basis of functional neuroimaging signals. However, our knowledge is limited because previous To2 measurements have been made at low temporal resolution (>100 ms). Here we recorded To2 at high temporal resolution (1 ms), simultaneously with co-localized field potentials, at several cortical depths from the whisker region of the somatosensory cortex in anaesthetized rats and mice. Stimulation of the whiskers produced rapid, laminar-specific changes in To2. Positive To2 responses (i.e. increases) were observed in the superficial layers within 50 ms of stimulus onset, faster than previously reported. Negative To2 responses (i.e. decreases) were observed in the deeper layers, with maximal amplitude in layer IV, within 40 ms of stimulus onset. The amplitude of the negative, but not the positive, To2 response correlated with local field potential amplitude. Disruption of neurovascular coupling, via nitric oxide synthase inhibition, abolished positive To2 responses to whisker stimulation in the superficial layers and increased negative To2 responses in all layers. Our data show that To2 responses occur rapidly following neuronal activity and are laminar dependent.

Self-administered, inhaled methoxyflurane improves patient comfort during nasoduodenal intubation for computed tomography enteroclysis for suspected small bowel disease: a randomized, double-blind, placebo-controlled trial.

AIM: To determine the efficacy and safety of self-administered, inhaled analgesic, methoxyflurane, used to improve patient comfort during computed tomography enteroclysis (CTE). MATERIALS AND METHODS: A randomized, double-blind, placebo-controlled trial was performed at two Australian hospitals (one tertiary referral public hospital and one private hospital). Patients were randomized to 3 ml methoxyflurane or saline (scented to maintain blindness) via hand-held inhaler. The main outcome measures were patient comfort during each stage of CTE and an overall rating as recorded by patients 1h post-procedure on a 10 cm visual analogue scale. Patient willingness to undergo repeat CTE, radiologist-rated ease of nasoduodenal intubation, and patient-rated ease of use of the inhaler were also assessed. RESULTS: Sixty patients (mean age 45 years; 41 women) were enrolled; 30 received methoxyflurane and were well matched to 30 receiving placebo. Procedural success was 98%. The mean dose of methoxyflurane consumed was 0.9 ml (SD 0.5). Patient comfort during nasoduodenal intubation was better with methoxyflurane {5.0 [95% confidence intervals (CI) 4.0-6.0]} than with placebo [2.7 (95% CI 1.8-3.7); p=0.002, t-test), but there were no significant differences for comfort levels at other times or overall. The inhaler was easy to use, was well tolerated, and there were no episodes of oxygen desaturation, aspiration, or anaphylaxis. CONCLUSIONS: Inhalational methoxyflurane safely improves patient comfort during nasoduodenal intubation, but does not improve overall procedure comfort.

In a randomized, double-blinded, placebo-controlled trial, the single oral dose typhoid vaccine, M01ZH09, is safe and immunogenic at doses up to 1.7 x 10(10) colony-forming units.

M01ZH09, S. Typhi (Ty2 Delta aroC Delta ssaV) ZH9, is a single oral dose typhoid vaccine with independently attenuating deletions. A phase II randomized, double-blind, placebo-controlled, dose-escalating trial evaluated the safety and immunogenicity of M01ZH09 to 1.7 x 10(10) colony-forming units (CFU). 187 Healthy adults received vaccine or placebo in four cohorts. Serologic responses and IgA ELISPOT were measured. At all doses, the vaccine was well tolerated and without bacteremias. One subject had a transient low-grade fever. 62.2-86.1% of subjects seroconverted S. Typhi-specific LPS IgG and 83.3-97.4% IgA; 92.1% had a positive S. Typhi LPS ELISPOT. M01ZH09 is safe and immunogenic up to 1.7 x 10(10)CFU. Efficacy testing of this single-dose oral typhoid vaccine is needed.

Clinical characteristics and outcomes of patients with vancomycin-susceptible Enterococcus faecalis and Enterococcus faecium bacteraemia--a five-year retrospective review.

The purpose of this study was to assess the epidemiology and outcomes of enterococcal bacteraemia. A retrospective review of demographic, microbiological and clinical data in patients 16 years of age and over with Enterococcus faecalis or E. faecium bacteraemia at Auckland City Hospital, New Zealand, from June 2002 to May 2007 was carried out. A total of 212 patients fulfilled the inclusion criteria, with 205 being included in the analysis. E. faecalis accounted for 86% (176/205) and E. faecium 14% (29/205) of the patients. Amoxycillin resistance occurred in 69% (20/29) of E. faecium isolates. High-level gentamicin resistance was present in 38% (65/171) of E. faecalis isolates and 25% (7/28) of E. faecium isolates (P = NS). No vancomycin-resistant enterococci were isolated. Healthcare association was present in 73% (149/205) of patients. Co-morbidities were present in 86% (176/205) of patients. The 7-day mortality was 13% (27/205) and the 30-day mortality 25% (52/205). On multivariate analysis, the 7-day mortality was statistically significantly associated with cirrhosis and shorter intravenous amoxycillin therapy. The 30-day mortality was statistically significantly associated with cirrhosis, malignancy, E. faecium bacteraemia and not receiving active antimicrobial therapy. No statistically significant association between high-level gentamicin resistance and mortality was demonstrated on multivariate analysis. Enterococcal bacteraemia occurs in a co-morbid, healthcare-exposed population. Associated mortality is high, and is associated with severe underlying disease, E. faecium bacteraemia and treatment factors.

Diagnostic and therapeutic approach to persistent or recurrent fevers of unknown origin in adult stem cell transplantation and haematological malignancy.

Persistent or recurrent fevers of unknown origin (PFUO) in neutropenic patients on broad-spectrum antibiotics have traditionally been treated with empirical antifungal therapy (EAFT). The lack of survival benefit seen with the use of amphotericin B deoxycholate (AmB-D) as EAFT has been attributed to its toxicities. More recently, newer, less toxic and more expensive antifungal agents such as the lipid formulations of AmB, the newer azoles (fluconazole, itraconazole and voriconazole) and caspofungin have been analysed in a number of EAFT trials. Compared with AmB-D the newer agents have superior safety but are of equivalent efficacy. This lack of survival advantage is related to the fact that the trigger for commencement of EAFT is late and non-specific. Thus, alternative approaches are required. New sensitive serological and molecular tests for the detection of Aspergillus antigens and genomic DNA have been developed and evaluated in accuracy studies. These tests have been incorporated into management strategies (i.e. pre-emptive strategies) to direct antifungal therapy. The pre-emptive approach has been shown to be safe and feasible but its impact on clinically important patient outcomes such as survival is less clear. Other advances include the introduction of effective, non-toxic mould-active antifungal prophylaxis and patient risk-group stratification. In this paper we provide new evidence-based algorithms for the diagnosis and treatment of PFUO in adult patients undergoing stem cell transplantation and chemotherapy for haematological malignancy which incorporate these newer diagnostic tests and are directed by the risk category of the patient and type of antifungal prophylaxis the patient is receiving.

An experimentally induced duplication of retinotopic mapping within the hamster primary visual cortex.

Primary cortical areas normally have a single mapping of the receptor array arising from a 'point-to-point' projection from the thalamus. We show that, for the visual cortex, this simple mapping rule breaks down when retinal input to the thalamus is altered. We utilize the monocular enucleation paradigm, which alters subcortical mappings ipsilateral to the remaining eye. We show that this manipulation produces an altered visuotopic map in area 17 with two separated, mirror-imaged representations of the central visual field. Furthermore, thalamic point-to-point connectivity is dramatically changed. There are now two overlapping geniculocortical projections: the predominant projection maps with apparently normal topography, and a second projection maps with the opposite polarity. The plane of symmetry of the duplicated anatomical projection coincides precisely with the functional map reversal and, notably, geniculocortical magnification factors are identical in the two projections. We suggest that the duplicated, abnormal geniculocortical projection is retinotopically matched to the normal projection. We speculate that aberrant geniculocortical terminals are stabilized because they have coherent activity patterns with topographically normal terminals.

Emergence of topography in the developing hamster retinocollicular projection: axial differences and the role of cell death.

The precise ordering of the hamster retinocollicular projection is established over the first two postnatal weeks, coincident with developmental cell death. We have used quantitative retrograde labelling to define topographic precision in the early postnatal projection, to describe its refinement and to assess the contribution played by selective retinal ganglion cell death. The hamster's short gestation period allows the investigation of events occurring prenatally in other rodents. Discrete injections of fluorescent beads in the superior colliculus followed by isodensity contour analysis of labelled retinal cells reveals a dramatic decrease in the extent of retina labelled between postnatal days 2, 6 and 12 (P2, P6, P12): the 20% contour encloses 38.3%, 8.3% and 1.8% of the retina at these ages. Paired injections of two different tracers at variable rostrocaudal (R-C) separations at P2 produced complete overlap of label even when injections were separated by over 1 mm. This was not true for paired mediolateral injections at P2 that were separated by more than 500 microm. Analysis of the segregation of the two tracers ('nearest-neighbour analysis') shows topography improving with age so that by P12 injections separated rostrocaudally by more than 500 microm produced no overlap in the retina. To examine the contribution of selective ganglion cell death to topographic refinement, animals given paired R-C injections at P2 were allowed to survive until P12. Nearest-neighbour analysis reveals significantly more order in the P2-P12 retinae than after overnight survival. Thus, selective cell death plays a small but appreciable role in correction of topographical errors.

Work beliefs and work status in epilepsy.

PURPOSE: The goal of this study was to determine differences in work beliefs between people with epilepsy who work and those who do not work. METHODS: One hundred thirteen subjects (58 females, 55 males) 41.56+/-11.42 years of age and with a seizure duration of 22.88+/-12.96 years (means+/-SD) were assessed. RESULTS: Forty percent worked full-time, 10% worked part-time, and 50% did not work. Twelve of the fifty-six who worked had more than one seizure per month, compared with 29 of 57 who did not work. There were significant differences between the working and nonworking groups: The nonworking group believed that (1) they had to work to be "normal," (2) they did not have enough education, (3) not having a job was the only barrier to independent living, (4) their families feared work injuries, (5) working represented a risk of injury, (6) they would hurt others if they had a seizure at work, (7) their families did not want them to work, and (8) seizures would negatively affect job performance. CONCLUSION: Work beliefs are important factors contributing to work status.