Effect of perinatal asphyxia on tuberomammillary nucleus neuronal density and object recognition memory: A possible role for histamine?

Perinatal asphyxia (PA) is associated with long-term neuronal damage and cognitive deficits in adulthood, such as learning and memory disabilities. After PA, specific brain regions are compromised, including neocortex, hippocampus, basal ganglia, and ascending neuromodulatory pathways, such as dopamine system, explaining some of the cognitive disabilities. We hypothesize that other neuromodulatory systems, such as histamine system from the tuberomammillary nucleus (TMN), which widely project to telencephalon, shown to be relevant for learning and memory, may be compromised by PA. We investigated here the effect of PA on (i) Density and neuronal activity of TMN neurons by double immunoreactivity for adenosine deaminase (ADA) and c-Fos, as marker for histaminergic neurons and neuronal activity respectively. (ii) Expression of the histamine-synthesizing enzyme, histidine decarboxylase (HDC) by western blot and (iii) thioperamide an H3 histamine receptor antagonist, on an object recognition memory task. Asphyxia-exposed rats showed a decrease of ADA density and c-Fos activity in TMN, and decrease of HDC expression in hypothalamus. Asphyxia-exposed rats also showed a low performance in object recognition memory compared to caesarean-delivered controls, which was reverted in a dose-dependent manner by the H3 antagonist thioperamide (5-10mg/kg, i.p.). The present results show that the histaminergic neuronal system of the TMN is involved in the long-term effects induced by PA, affecting learning and memory.

Total and unbound darunavir pharmacokinetics in pregnant women infected with HIV-1: results of a study of darunavir/ritonavir 600/100 mg administered twice daily

Objectives

Antiretroviral therapy during pregnancy is recommended to reduce the risk of mother-to-child transmission of HIV and for maternal care management. Physiological changes during pregnancy can affect pharmacokinetics, potentially altering pharmacological activity. We therefore evaluated the pharmacokinetics of twice-daily (bid) darunavir in HIV-1-infected pregnant women.

Methods

HIV-1-infected pregnant women receiving an antiretroviral regimen containing darunavir/ritonavir 600/100 mg bid were enrolled in this study. Total and unbound darunavir and total ritonavir plasma concentrations were obtained over 12 h during the second and third trimesters and postpartum. Total darunavir and ritonavir plasma concentrations were determined using a validated high-performance liquid chromatography tandem mass spectrometry assay and unbound darunavir was determined using ¹⁴C-darunavir-fortified plasma. Pharmacokinetic parameters were derived using noncompartmental analysis.

Results

Data were available for 14 women. The area under the plasma concentration–time curve from 0 to 12 h (AUC_12h) for total darunavir was 17–24% lower during pregnancy than postpartum. The AUC_12h for unbound darunavir was minimally reduced during pregnancy vs. postpartum. The minimum plasma concentration (C_min) of total and unbound darunavir was on average 43–86% and 10–14% higher, respectively, during pregnancy vs. postpartum. The antiviral response (< 50 HIV-1 RNA copies/mL) was 33% at baseline and increased to 73–90% during treatment; the percentage CD4 count increased over time. One serious adverse event was reported (increased transaminase). All 12 infants born to women remaining in the study at delivery were HIV-1-negative; four of these infants were premature.

Conclusions

Total darunavir exposure decreased during pregnancy. No clinically relevant change in unbound (active) darunavir occurred during pregnancy, suggesting that no dose adjustment is required for darunavir/ritonavir 600/100 mg bid in pregnant women.

Chronic fluoxetine treatment induces structural plasticity and selective changes in glutamate receptor subunits in the rat cerebral cortex

It has been postulated that chronic administration of antidepressant drugs induces delayed structural and molecular adaptations at glutamatergic forebrain synapses that might underlie mood improvement. To gain further insight into these changes in the cerebral cortex, rats were treated with fluoxetine (flx) for 4 weeks. These animals showed decreased anxiety and learned helplessness. N-methyl-d-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor subunit levels (NR1, NR2A, NR2B, GluR1 and GluR2) were analysed in the forebrain by both western blot of homogenates and immunohistochemistry. Both methods demonstrated an upregulation of NR2A, GluR1 and GluR2 that was especially significant in the retrosplenial granular b cortex (RSGb). However, when analysing subunit content in postsynaptic densities and synaptic membranes, we found increases of NR2A and GluR2 but not GluR1. Instead, GluR1 was augmented in a microsomal fraction containing intracellular membranes. NR1 and GluR2 were co-immunoprecipitated from postsynaptic densities and synaptic membranes. In the immunoprecipitates, NR2A was increased while GluR1 was decreased supporting a change in receptor stoichiometry. The changes of subunit levels were associated with an upregulation of dendritic spine density and of large, mushroom-type spines. These molecular and structural adaptations might be involved in neuronal network stabilization following long-term flx treatment.

Antagonistic effects of TrkB and p75NTRon NMDA receptor currents in post-synaptic densities transplanted into Xenopus oocytes

Brain-derived neurotrophic factor (BDNF) and its receptor TrkB are essential regulators of synaptic function in the adult CNS. A TrkB-mediated effect at excitatory synapses is enhancement of NMDA receptor (NMDA-R)-mediated currents. Recently, opposing effects of TrkB and the pan-neurotrophin receptor p75(NTR) on long-term synaptic depression and long-term potentiation have been reported in the hippocampus. To further study the regulation of NMDA-Rs by neurotrophin receptors in their native protein environment, we micro-transplanted rat forebrain post-synaptic densities (PSDs) into Xenopus oocytes. One-minute incubations of oocytes with BDNF led to dual effects on NMDA-R currents: either TrkB-dependent potentiation or TrkB-independent inhibition were observed. Pro-nerve growth factor, a ligand for p75(NTR) but not for TrkB, produced a reversible, dose-dependent, TrkB-independent and p75(NTR)-dependent inhibition of NMDA-Rs. Fractionation experiments showed that p75(NTR) is highly enriched in the PSD protein fraction. Immunoprecipitation and pull-down experiments further revealed that p75(NTR) is a core component of the PSD, where it interacts with the PDZ3 domain of the scaffolding protein SAP90/PSD-95. Our data provide striking evidence for a rapid inhibitory effect of p75(NTR) on NMDA-R currents that antagonizes TrkB-mediated NMDA-R potentiation. These opposing mechanisms might be present in a large proportion of forebrain synapses and may contribute importantly to synaptic plasticity.

Clinically relevant doses of fluoxetine and reboxetine induce changes in the TrkB content of central excitatory synapses

We have studied the effect of low doses of two widely used antidepressants, fluoxetine (Flx) and reboxetine (Rbx), on excitatory synapses of rat brain cortex and hippocampus. After 15 days of Flx treatment (0.67 mg/kg/day), its plasma level was 20.7+/-5.6 ng/ml. Analysis of postsynaptic densities (PSDs) by immunoblotting revealed no changes in the glutamate receptor subunits GluR1, NR1, NR2A/B, mGluR1alpha nor in the neurotrophin receptor p75(NTR). However, the brain-derived neurotrophic factor (BDNF) receptor TrkB decreased by 42.8+/-6%, and remained decreased after 6 weeks of treatment. The BDNF and TrkB content in homogenates of cortex and hippocampus began to rise at 9 and 15 days, respectively, and remained high for up to 6 weeks. Similar results were obtained following chronic Rbx administration at 0.128 mg/kg/day. We propose that BDNF, whose synthesis is increased by antidepressants, and which is in part released at synaptic sites, binds to TrkB in PSDs, leading to the internalization of the BDNF-TrkB complex and, thus, to a decrease of TrkB in the PSDs. This was paralleled by greater levels of phosphorylated (ie activated) TrkB in the light membrane fraction, that contains signaling endosomes. The retrograde transport of endocyted BDNF/TrkB complexes from spines to cell bodies, where it activates the synthesis of more BDNF, is a protracted process, potentially requiring several cycles of TrkB/BDNF complex endocytosis and transport. This positive feedback mechanism may help explain the time-lag between drug administration and its therapeutic effect, that is, the antidepressant drug paradox.

Laryngeal pseudosulcus as a predictor of laryngopharyngeal reflux

OBJECTIVES/HYPOTHESIS

Laryngeal pseudosulcus is an accurate prognostic indicator of laryngopharyngeal reflux (LPR) disease.

STUDY DESIGN

Prospective study of 20 consecutive patients with laryngeal pseudosulcus. Pseudosulcus is infraglottic laryngeal edema that is thought to be secondary to LPR. All patients were evaluated with dual-channel pH probe 24-hour monitoring to evaluate for the presence of laryngopharyngeal reflux.

METHODS

Twenty patients identified with laryngeal pseudosulcus on routine physical examination were included in the study. Each patient underwent a 24-hour dual-channel pH probe. The data were analyzed and compared with previously published normative data. The data included the total number of reflux episodes and the percentage of time the pH dropped below 4 at the proximal probe.

RESULTS

Eighteen of the 20 patients with laryngeal pseudosulcus were found to have LPR. The mean number of reflux episodes at the proximal probe was 29.4 (range, 3-82). The mean percentage of time the pH dropped below 4 was 1.15%. In the upright position the mean value was 1.59% and in the supine position it was 0.19%. This gives pseudosulcus a positive predictive value for LPR of 90%.

CONCLUSION

This study shows laryngeal pseudosulcus to be an accurate predictor of laryngopharyngeal reflux disease.

Mosquitoes (Diptera: Culicidae) captured in the Iquitos area of Peru

A mosquito capture program was initiated to study mosquito species and their potential for arboviral transmission in the Peruvian Amazon. More than 35,000 mosquitoes of 13 different genera and at least 25 species were captured in urban and sylvan sites in the Iquitos area. These findings represent the first published list of Peruvian mosquitoes since 1971 and the first such list from the Peruvian Amazon.

Plasmodium vivax VK247 and VK210 circumsporozoite proteins in Anopheles mosquitoes from Andoas, Peru

Anopheles mosquitoes captured in Andoas, Peru, a Plasmodium vivax-endemic area in the Peruvian Amazon region, contained both VK210 and VK247 P. vivax circumsporozoite (CS) proteins. Approximately 0.9% of the 4,403 mosquitoes tested by enzyme-linked immunosorbent assay were positive; 28% and 72% of the positive mosquitoes contained VK210 and VK247 CS proteins, respectively. These findings correlate strongly with a recent report of the presence of antibodies in residents of this area that recognize the VK210 and VK247 repeats, clearly indicating that both P. vivax CS protein polymorphs are common in the region.