Modulation of olfactory bulb network activity by serotonin: synchronous inhibition of mitral cells mediated by spatially localized GABAergic microcircuits.

Although inhibition has often been proposed as a central mechanism for coordinating activity in the olfactory system, relatively little is known about how activation of different inhibitory local circuit pathways can generate coincident inhibition of principal cells. We used serotonin (5-HT) as a pharmacological tool to induce spiking in ensembles of mitral cells (MCs), a primary output neuron in the olfactory bulb, and recorded intracellularly from pairs of MCs to directly assay coincident inhibitory input. We find that 5-HT disynaptically depolarized granule cells (GCs) only slightly but robustly increased the frequency of inhibitory postsynaptic inhibitory currents in MCs. Serotonin also triggered more coincident IPSCs in pairs of nearby MCs than expected by chance, including in MCs with truncated apical dendrites that lack glomerular synapses. That serotonin-triggered coincident inhibition in the absence of elevated GC somatic firing rates suggested that synchronized MC inhibition arose from glutamate receptor-mediated depolarization of GC dendrites or other (non-GC) interneurons outside the glomerular layer. Tetanic stimulation of GCL afferents to GCs triggered robust GC spiking, coincident inhibition in pairs of MCs, and recruited large-amplitude IPSCs in MCs. Enhancing neurotransmission through NMDARs by lowering the external Mg2+ concentration also increased inhibitory tone onto MCs but failed to promote synchronized inhibition. These results demonstrate that coincident MC inhibition can occur through multiple circuit pathways and suggests that the functional coordination between different GABAergic synapses in individual GCs can be dynamically regulated.

Fitness costs limit influenza A virus hemagglutinin glycosylation as an immune evasion strategy.

Here, we address the question of why the influenza A virus hemagglutinin (HA) does not escape immunity by hyperglycosylation. Uniquely among dozens of monoclonal antibodies specific for A/Puerto Rico/8/34, escape from H28-A2 neutralization requires substitutions introducing N-linked glycosylation at residue 131 or 144 in the globular domain. This escape decreases viral binding to cellular receptors, which must be compensated for by additional substitutions in HA or neuraminidase that enable viral replication. Sequence analysis of circulating H1 influenza viruses confirms the in vivo relevance of our findings: natural occurrence of glycosylation at residue 131 is always accompanied by a compensatory mutation known to increase HA receptor avidity. In vaccinated mice challenged with WT vs. H28-A2 escape mutants, the selective advantage conferred by glycan-mediated global reduction in antigenicity is trumped by the costs of diminished receptor avidity. These findings show that, although N-linked glycosylation can broadly diminish HA antigenicity, fitness costs restrict its deployment in immune evasion.

Obstetrical and perinatal outcomes of patients with methamphetamine-positive drug screen on labor and delivery.

BACKGROUND: The incidence of methamphetamine use in reproductive-age women across the United States is increasing. The existing literature on methamphetamine use in pregnancy has indicated an elevated risk of adverse maternal and neonatal health outcomes. OBJECTIVE: This study aimed to investigate pregnancy outcomes in patients with recent methamphetamine use compared with patients who received negative test results for methamphetamine at the time of delivery. STUDY DESIGN: A single-site retrospective cohort study from January to December 2015 was performed. Patients with a documented urine drug screen during the delivery encounter were identified from the electronic medical records. The outcomes of patients with methamphetamine-positive urine drug screens were compared with controls with urine drug screens negative for methamphetamine. Maternal outcomes of interest included placental abruption, hypertensive disorders, premature preterm rupture of membranes, postpartum hemorrhage, and preterm birth. Utilization of prenatal care, social work consults, and child protective services referrals were also recorded. Neonatal outcomes included birthweight, neonatal intensive care unit length of stay, Apgar scores, and perinatal mortality. RESULTS: The 2 groups had similar demographic characteristics (age, multiparity, ethnicity), with the methamphetamine-positive group more likely to have no or limited prenatal care. Both groups engaged in polysubstance use. A methamphetamine-positive urine drug screen at the time of delivery carries an increased risk of abruption (odds ratio, 5.63; confidence interval, 1.21-26.21) but indicated no increased risk of maternal hypertensive disorders. Additional associated risks include preterm birth (odds ratio, 3.10; confidence interval, 1.44-6.68), lower Apgar scores at 1 and 5 minutes (P=.012 and P=.02, respectively), and increased perinatal mortality (odds ratio, 6.9; confidence interval, 1.01-47.4). CONCLUSION: Positive urine drug testing for methamphetamines during labor admission confers considerable maternal and perinatal morbidity and mortality including an increased risk of placental abruption, preterm birth, and perinatal demise. Given the limited treatments for methamphetamine addiction, further research is urgently needed.

An open-label controlled trial of theophylline for treatment of patients with hyposmia.

BACKGROUND: To test the hypothesis that theophylline is effective in correcting smell loss in patients with hyposmia. METHODS: Three hundred twelve patients with smell loss (hyposmia) were evaluated to determine characteristics of their loss by psychophysical measurements of detection and recognition thresholds, magnitude estimation and hedonic values for 4 odors (pyridine, nitrobenzene, thiophene, and amyl acetate) by use of a forced-choice 3-stimuli staircase design previously documented in a double-blind study. Patients were then treated in a fixed design open-label clinical trial with oral theophylline. Drug was given in equal divided doses from 200 to 800 mg daily for 2- to 8-month periods and subjective and psychophysical measurements of smell function and blood theophylline levels were measured; results were compared with those obtained before treatment. RESULTS: Subjective smell loss improved in 157 (50.3%) patients; smell function was considered normal by 34 (21.7%). Overall, 10.9% of patients in the study considered smell function returned to normal. However, measurements of mean detection and recognition thresholds improved significantly at each drug level; measurements of mean magnitude estimation and hedonic also improved. Improvement was greater at drug doses of 600 and 800 mg than at 200 or 400 mg. Once improvement occurred, as long as treatment was maintained, it persisted for as long as follow-up was measured. CONCLUSION: Theophylline was effective in improving smell function in patients with smell loss. Improvement persisted as long as treatment was continued, which extended from 6 to 72 months.

Interleukin 6 in hyposmia.

IMPORTANCE: Olfaction is a complex sensory process that has not been fully studied. Elevated plasma levels of interleukin 6 (IL-6) have been found in patients with several acute and chronic diseases but have not been reported in patients with smell loss (hyposmia). OBJECTIVE: To determine IL-6 levels in patients with hyposmia. DESIGN: Retrospective study. All measurements were made without reference to the origin of any collected sample. SETTING An ambulatory private practice at The Taste and Smell Clinic in Washington, DC. PARTICIPANTS: Fifty-nine consecutive patients who presented to the clinic between 2005 and 2008 for evaluation and treatment of various degrees of hyposmia were studied. Nine volunteers with normal sensory function served as controls. MAIN OUTCOMES AND MEASURES: Levels of IL-6 were measured in samples of plasma, urine, saliva, and nasal mucus. RESULTS: All biological fluid samples studied contained IL-6. Mean (SEM) levels in plasma, saliva, and nasal mucus in patients were significantly higher than in controls (0.95 [0.10] vs 0.12 [0.03] pg/mL, 0.57 [0.05] vs 0.30 [0.01] pg/mL, and 29.7 [3.8] vs 11.6 [0.5] pg/mL, respectively; all P < .001). The concentration of IL-6 in nasal mucus in patients was significantly higher than in controls and was more than 30 times higher than in any other biological fluid. Mean (SEM) levels in urine were not significantly different: 0.92 (0.17) pg/mL for patients and 1.26 (0.41) pg/mL for controls (P > .50). CONCLUSIONS AND RELEVANCE: Compared with controls, IL-6 in patients was significantly elevated in plasma, saliva, and nasal mucus. Because IL-6 is a proinflammatory cytokine, these changes can relate to local or systemic inflammatory processes, which can be a cause or a result of pathological processes associated with hyposmia. These results support the concept that hyposmia has a biochemical basis and IL-6 may play a role in biochemical pathological processes underlying hyposmia and its treatment.

Relative resistance to oral theophylline treatment in patients with hyposmia manifested by decreased secretion of nasal mucus cyclic nucleotides.

INTRODUCTION: Oral treatment with the phosphodiesterase inhibitor theophylline in an open-label fixed-design clinical trial in 312 patients with hyposmia improved smell function in >50%. Before treatment, all patients had lower than normal levels of nasal mucus cAMP and cGMP. The purpose of this study was to study relationships among changes in smell function, theophylline levels and nasal mucus cAMP and cGMP among patients whose smell function improved (responders) and those who did not improve (nonresponders) on oral theophylline treatment. METHODS: After all data analysis from the clinical trial was completed, data from each of the 31 of the 312 patients in whom nasal mucus cAMP and cGMP and theophylline levels were available before and after theophylline treatment at several drug doses were evaluated. At initiation and at termination of each treatment, dose smell function, nasal mucus cAMP and cGMP and plasma theophylline were analyzed. RESULTS: On the same theophylline dose, although serum theophylline increased among both responders and nonresponders, serum levels were consistently higher among responders. Nasal mucus cAMP and cGMP were also higher among responders than nonresponders. At higher theophylline doses, cGMP reached normal levels among responders, whereas it did not change significantly among nonresponders. CONCLUSIONS: Some patients with hyposmia with initially low nasal mucus cAMP and cGMP levels may be relatively resistant to oral theophylline treatment. This result may offer a mechanism of response lack among some patients whose smell function did not improve after oral theophylline treatment although other factors may influence their response lack.

Influenza A virus hemagglutinin antibody escape promotes neuraminidase antigenic variation and drug resistance.

Drugs inhibiting the influenza A virus (IAV) neuraminidase (NA) are the cornerstone of anti-IAV chemotherapy and prophylaxis in man. Drug-resistant mutations in NA arise frequently in human isolates, limiting the therapeutic application of NA inhibitors. Here, we show that antibody-driven antigenic variation in one domain of the H1 hemagglutinin Sa site leads to compensatory mutations in NA, resulting in NA antigenic variation and acquisition of drug resistance. These findings indicate that influenza A virus resistance to NA inhibitors can potentially arise from antibody driven HA escape, confounding analysis of influenza NA evolution in nature.

Hemagglutinin receptor binding avidity drives influenza A virus antigenic drift.

Rapid antigenic evolution in the influenza A virus hemagglutinin precludes effective vaccination with existing vaccines. To understand this phenomenon, we passaged virus in mice immunized with influenza vaccine. Neutralizing antibodies selected mutants with single-amino acid hemagglutinin substitutions that increased virus binding to cell surface glycan receptors. Passaging these high-avidity binding mutants in naïve mice, but not immune mice, selected for additional hemagglutinin substitutions that decreased cellular receptor binding avidity. Analyzing a panel of monoclonal antibody hemagglutinin escape mutants revealed a positive correlation between receptor binding avidity and escape from polyclonal antibodies. We propose that in response to variation in neutralizing antibody pressure between individuals, influenza A virus evolves by adjusting receptor binding avidity via amino acid substitutions throughout the hemagglutinin globular domain, many of which simultaneously alter antigenicity.