Increased risk of breakthrough infection among cytomegalovirus donor-positive/recipient-negative kidney transplant recipients receiving lower-dose valganciclovir prophylaxis.

OBJECTIVE: We compared the effectiveness of lower-dose (LD) (450 mg/day for 6 months) to standard-dose (SD) (900 mg/day for 6 months) valganciclovir (VGCV) prophylaxis for prevention of cytomegalovirus (CMV) infection and disease in high-risk CMV donor-positive/recipient-negative (D+/R-) kidney recipients. METHODS: We performed a single-center, retrospective cohort study, in a 750-bed academic medical center, involving a total of 90 evaluable CMV high-risk kidney recipients. All patients were retrospectively followed from day of transplantation to November 1, 2012, or to the development of CMV infection or disease, death, or loss to follow-up. CMV screening was only done if suggestive symptoms or abnormal laboratory values were present. Our immunosuppressive protocol otherwise did not differ between periods. RESULTS: In total, 45 consecutive eligible patients initiated SD prophylaxis in the 22 months before the institutional protocol change regarding CMV prophylaxis. One patient developed CMV infection in the setting of non-adherence. In the 16 months after the protocol update, 45 consecutive eligible patients receiving LD prophylaxis were evaluated: 6 developed CMV infection while receiving prophylaxis (P = 0.11). Ganciclovir (GCV)-resistant infection was confirmed in 1 patient in the LD prophylaxis group. Late-onset CMV infection or disease occurred in 11 patients (24%) in the SD group and in 12 patients (27%) in the LD group (P = 0.86). More patients in the SD group developed leukopenia (75% vs. 44%, P < 0.01). During the study period, no significant differences were seen between the groups in mean mg/kg exposure to rabbit anti-thymocyte globulin induction courses, mean tacrolimus troughs, number of rejection episodes, mean estimated renal function, graft survival, or patient survival. Overall mean follow-up (± standard deviation) was 357 days (± 53) in the SD group and 320 days (± 103) in the LD group (P = 0.03). CONCLUSION: Breakthrough CMV infection while receiving VGCV prophylaxis occurred more often after the institutional protocol revision to LD VGCV prophylaxis. Given our concern for increased risk of breakthrough infection and GCV resistance when prophylaxis is under-dosed, our institutional protocols were revised back to SD prophylaxis for all CMV D+/R- kidney transplant recipients.

Review: A theoretical framework to define foraging behaviour syndromes in ruminants using wearable technologies.

Due to intensification processes that have had negative impacts on environmental externalities, pastoral farmers, worldwide, are facing increasing scrutiny and pressure from consumers, governments, and the public to reduce the environmental footprint of their operations. Developing tools and systems that farmers can use to maintain profitability and productivity while decreasing the negative externalities of their operations is important for the vitality of rural sectors. Capitalising on individual animal variation has been promoted as an opportunity to increase animal productivity and enhance welfare while decreasing the negative environmental impacts of pastoral farming. Of particular interest are behaviours that are associated with foraging, as these are the primary drivers of variation in animal performance in pastoral farming. Developing a methodology that can identify consistent foraging behavioural variations across individuals is a critical step in making this a practical solution for farmers and herders. As with all behavioural research, the fundamental challenge is selecting the appropriate behaviours to measure. Understanding the contextual drivers of behavioural expression is a major development in this process. Herd management and composition, environmental variables and many more contexts alter the expression of behaviours, so how do we capture behaviours of interest? We propose the use of a systematic methodology to capture behaviours of significance from large groups of foraging ruminants using wearable technology, namely Global Positioning System and accelerometers. This contrasts with traditional reductionist methodologies used in behaviour research and has the benefit of providing large objective datasets from undisturbed animals. Statistical analysis of the data will inform behaviours of interest that are clustered together to inform a three-factor foraging behaviour syndrome model adapted from the animal five-factor model (activity, aggression, boldness, exploration, sociability) of personality. Syndromes, unlike personalities, include correlated suites of behaviours that are expressed across spatial and temporal contexts. By capturing foraging behaviour syndromes, selection can be used to match appropriate syndromes to different pastoral farming landscapes, thereby potentially improving the system's productivity while reducing their negative environmental impact.

Temporal trends and predictors of phthalate, phthalate replacement, and phenol biomarkers in the LIFECODES Fetal Growth Study.

BACKGROUND: Exposure to many phthalates and phenols is declining as replacements are introduced. There is little information on temporal trends or predictors of exposure to these newer compounds, such as phthalate replacements, especially among pregnant populations. OBJECTIVE: Examine temporal trends and predictors of exposure to phthalates, phthalate replacements, and phenols using single- and multi-pollutant approaches. METHODS: We analyzed data from 900 singleton pregnancies in the LIFECODES Fetal Growth Study, a nested case-cohort with recruitment from 2007 to 2018. We measured and averaged concentrations of 12 phthalate metabolites, four phthalate replacement metabolites, and 12 phenols in urine at three timepoints during pregnancy. We visualized and analyzed temporal trends and predictors of biomarker concentrations. To examine chemical mixtures, we derived clusters of individuals with shared exposure profiles using a finite mixture model and examined temporal trends and predictors of cluster assignment. RESULTS: Exposure to phthalates and most phenols declined across the study period, while exposure to phthalate replacements (i.e., di(isononyl) cyclohexane-1,2-dicarboxylic acid, diisononyl ester [DINCH] and di-2-ethylhexyl terephthalate [DEHTP]) and bisphenol S (BPS) increased. For example, the sum of DEHTP biomarkers increased multiple orders of magnitude, with an average concentration of 0.92 ng/mL from 2007 to 2008 and 61.9 ng/mL in 2017-2018. Biomarkers of most chemical exposures varied across sociodemographic characteristics, with the highest concentrations observed in non-Hispanic Black or Hispanic participants relative to non-Hispanic White participants. We identified five clusters with shared exposure profiles and observed temporal trends in cluster membership. For example, at the end of the study period, a cluster characterized by high exposure to phthalate replacements was the most prevalent. SIGNIFICANCE: In a large and well-characterized pregnancy cohort, we observed exposure to phthalate replacements and BPS increased over time while exposure to phthalates and other phenols decreased. Our results highlight the changing nature of exposure to consumer product chemical mixtures.

Morphine-naloxone interactions: a role for nonspecific morphine excitatory effects in withdrawal.

The opiate antagonist naloxone precipitates withdrawal when given either 15 minutes after or 1 minute before a single injection of morphine in drug-naïve mice. We propose that withdrawal signs arise from a synergistic mixture of excitatory influences that are direct (agonistic action on nonspecific opiate receptors) and indirect (sensory and affective disorders, stress, hormonal and neurotransmitter dysfunction, and so forth). The predominant effects during precipitated withdrawal are assumed to be direct, whereas during abstinence in tolerant animals they are indirect.

Taking cell-matrix adhesions to the third dimension.

Adhesions between fibroblastic cells and extracellular matrix have been studied extensively in vitro, but little is known about their in vivo counterparts. Here, we characterized the composition and function of adhesions in three-dimensional (3D) matrices derived from tissues or cell culture. "3D-matrix adhesions" differ from focal and fibrillar adhesions characterized on 2D substrates in their content of alpha5beta1 and alphavbeta3 integrins, paxillin, other cytoskeletal components, and tyrosine phosphorylation of focal adhesion kinase (FAK). Relative to 2D substrates, 3D-matrix interactions also display enhanced cell biological activities and narrowed integrin usage. These distinctive in vivo 3D-matrix adhesions differ in structure, localization, and function from classically described in vitro adhesions, and as such they may be more biologically relevant to living organisms.

The physiology of brain histamine.

Histamine-releasing neurons are located exclusively in the TM of the hypothalamus, from where they project to practically all brain regions, with ventral areas (hypothalamus, basal forebrain, amygdala) receiving a particularly strong innervation. The intrinsic electrophysiological properties of TM neurons (slow spontaneous firing, broad action potentials, deep after hyperpolarisations, etc.) are extremely similar to other aminergic neurons. Their firing rate varies across the sleep-wake cycle, being highest during waking and lowest during rapid-eye movement sleep. In contrast to other aminergic neurons somatodendritic autoreceptors (H3) do not activate an inwardly rectifying potassium channel but instead control firing by inhibiting voltage-dependent calcium channels. Histamine release is enhanced under extreme conditions such as dehydration or hypoglycemia or by a variety of stressors. Histamine activates four types of receptors. H1 receptors are mainly postsynaptically located and are coupled positively to phospholipase C. High densities are found especially in the hypothalamus and other limbic regions. Activation of these receptors causes large depolarisations via blockade of a leak potassium conductance, activation of a non-specific cation channel or activation of a sodium-calcium exchanger. H2 receptors are also mainly postsynaptically located and are coupled positively to adenylyl cyclase. High densities are found in hippocampus, amygdala and basal ganglia. Activation of these receptors also leads to mainly excitatory effects through blockade of calcium-dependent potassium channels and modulation of the hyperpolarisation-activated cation channel. H3 receptors are exclusively presynaptically located and are negatively coupled to adenylyl cyclase. High densities are found in the basal ganglia. These receptors mediated presynaptic inhibition of histamine release and the release of other neurotransmitters, most likely via inhibition of presynaptic calcium channels. Finally, histamine modulates the glutamate NMDA receptor via an action at the polyamine binding site. The central histamine system is involved in many central nervous system functions: arousal; anxiety; activation of the sympathetic nervous system; the stress-related release of hormones from the pituitary and of central aminergic neurotransmitters; antinociception; water retention and suppression of eating. A role for the neuronal histamine system as a danger response system is proposed.

Opposite modulation of histaminergic neurons by nociceptin and morphine.

We have studied the effects of nociceptin/orphanin FQ on the histaminergic neurons in the tuberomammillary (TM) nucleus and compared them with the actions of opioid agonists. Intracellular recordings of the membrane potential were made with sharp electrodes from superfused rat hypothalamic slices. Nociceptin strongly inhibited the firing of the TM neurons. In the concentration range 10-300 nM, nociceptin hyperpolarized the neurons in a dose-dependent and reversible manner. Insensitivity to tetrodotoxin indicated a postsynaptic effect which was associated with decreased input resistance. Voltage-current plots suggested the involvement of a potassium conductance which was highly sensitive to Ba(2+) and decreased by Cs(+), in keeping with the activation of an inwardly rectifying potassium channel. Morphine (20-100 microM) depolarized the TM neurons and increased their firing, and this effect was blocked by tetrodotoxin. Dynorphin A(1-13) at 100-300 nM did not affect the TM neurons. Nociceptin and morphine modulate the activity of the TM neurons, and most likely histamine release, in opposite ways. Histamine has an antinociceptive effect in the brain and may be involved in opioid-induced analgesia. Nociceptin might therefore influence pain transmission by inhibiting opioid-induced histamine release from the TM nucleus and also modulate other physiological mechanisms which have been ascribed to the histaminergic system.

Serotonin excites tuberomammillary neurons by activation of Na(+)/Ca(2+)-exchange.

We have studied the effects of serotonin on the histaminergic neurons in the hypothalamic tuberomammillary nucleus. Intracellular recordings of the membrane potential were made with sharp electrodes from superfused rat hypothalamic slices. We found that serotonin increased the firing rate of the neurons to 224% of the control rate and depolarized them dose-dependently. Insensitivity to tetrodotoxin indicated a postsynaptic effect, which was unrelated to any conductance change. The involved receptor appeared to be a 5-HT2C receptor. The depolarization was strongly dependent on temperature and replacement of extracellular Na(+) with Li(+) or with N-methyl-D-glucamine suppressed the depolarization. Pretreatment with Ni(2+), 2',4'-dichlorobenzamil or KB-R7943 strongly attenuated the effect. These features indicate that the depolarization is the result of activation of an electrogenic Na(+)/Ca(2+)-exchanger which leads to an net inward current. These results support the view that the Na(+)/Ca(2+)-exchanger can play a role in determining the excitability of neurons. The results also provide a functional connection between two transmitter systems, the histaminergic and serotonergic, which modulate many physiological functions in the brain.

Histamine H(3) receptors depress synaptic transmission in the corticostriatal pathway.

The effect of histamine on the main input to the striatum - the corticostriatal pathway - was studied using electrophysiological techniques in brain slices from rats and mice. Field potentials (FPs) were recorded in the striatum following stimulation at the border of the striatum and the cortex. Bath application of histamine caused a pronounced and long-lasting depression of FPs in rat slices with an IC(50) of 1.6 microM and a maximal depression of around 40%. In mouse slices histamine also depressed FPs, but to a lesser extent and more transiently. Further experiments in rat slices showed that histamine H(3) receptors were responsible for this depression since the selective H(3) receptor agonist R-alpha-methylhistamine (1 microM) mimicked the action of histamine whilst the selective H(3) receptor antagonist, thioperamide (10 microM) blocked the depression caused by histamine application. The histaminergic depression was probably not mediated indirectly through interneurons since blockade of GABA(A), GABA(B), nicotinic and muscarinic receptors or nitric oxide synthase did not prevent the histamine effect. Intracellular recordings from medium spiny neurons in the striatum revealed that histamine did not affect postsynaptic membrane properties but increased paired-pulse facilitation of excitatory synaptic responses indicating a presynaptic locus of action.

A persistent sodium current in acutely isolated histaminergic neurons from rat hypothalamus.

Histamine neurons acutely dissociated from the tuberomammillary nucleus of the rat hypothalamus were studied in whole-cell and cell-attached patch-clamp experiments. Electrophysiological properties of dissociated cells were found to be similar to those recorded in slice experiments using microelectrodes. Tuberomammillary neurons fired spontaneously and this activity persisted when Cs+ (1.5 mM) was added to, or when K+ was removed from the extracellular solution. In whole-cell experiments a persistent tetrodotoxin-sensitive inward current was recorded. In cell attached recordings voltage-gated sodium channels displayed either normal or non-inactivating behavior. These results provide a further analysis of the properties of histaminergic neurons and indicate that spontaneous activity is intrinsic to individual neurons. Evidence for a non-inactivating tetrodotoxin-sensitive sodium current is presented. Single channel recordings indicate that this current is the result of non-inactivating behavior of sodium channels. Such a current is well suited for biasing tuberomammillary neurons toward spontaneous activity.

Serotonin1 and serotonin2 receptors hyperpolarize and depolarize separate populations of medial pontine reticular formation neurons in vitro.

The action of serotonin on medial pontine reticular formation neurons was examined using intracellular electrophysiological methods in rat brainstem slices in vitro. A hyperpolarization associated with a decrease in input resistance was elicited by serotonin in 34% of the neurons, and a depolarization associated with an increase in input resistance was produced in 56% of the neurons. Both responses persisted in the presence of tetrodotoxin. The hyperpolarization resulted from a steady-state increase in outward current which varied with the external potassium concentration in a manner consistent with a conductance increase primarily to this ion. This response was mimicked by the serotonin1 agonist, 5-carboxamidotryptamine, as well as by the serotonin1a agonist, 8-hydroxy-dipropyl aminotetralin hydrobromide, and was blocked by spiperone, an antagonist of serotonin1 sites. The depolarization resulted from a steady-state decrease in outward current which varied with external potassium. The depolarization was mimicked by the serotonin2 agonist, alpha-methyl-5-hydroxytryptamine, and was blocked by the serotonin2 antagonist, ketanserin. Neither of these agents had any effect upon serotonin-induced hyperpolarizations. In conclusion, the excitability of medial pontine reticular formation neurons is influenced by serotonin acting to increase or decrease potassium conductance(s). These opposing effects reflect actions on distinct serotonin receptor subtypes that are segregated to distinct populations of medial pontine reticular formation neurons.

Glycine-mediated inhibitory postsynaptic potentials in the medial pontine reticular formation of the rat in vitro.

Glycinergic neurotransmission was examined in rat medial pontine reticular formation neurons in vitro. Intracellular recordings using glass microelectrodes were made in acutely prepared brainstem slices 400 microns thick. Spontaneous and electrically evoked synaptic activity was blocked by the glycine antagonist strychnine (1-5 microM) but not by the GABA antagonists bicuculline methiodide (40 microM) or picrotoxin (40 microM). Strychnine-sensitive spontaneous and evoked postsynaptic potentials persisted in the presence of the glutamate antagonist (kynurenate, 1 mM). Whole-cell voltage-clamp recordings were carried out in organotypic cultures of rat brainstem. The reversal potential of synaptic currents and responses to exogenously applied glycine were similar and were sensitive to manipulations of the chloride equilibrium potential. Synaptic activity but not responses to exogenous glycine were blocked by tetrodotoxin (0.3 microM). These results indicate the presence of robust, chloride ion-mediated glycinergic inhibition of medial pontine reticular formation neurons, and suggest that glycinergic neurons play an important role in controlling pontine premotor circuitry.

Nicotinic depolarizations of rat medial pontine reticular formation neurons studied in vitro.

Either muscarinic or nicotinic cholinergic activation of the medial pontine reticular formation evokes a behavioral state, indistinguishable in most respects from that of natural rapid eye movement sleep. However, the presence of physiologically relevant nicotonic receptors has not been described. Intracellular current and single electrode voltage clamp recordings were used to analyse the electrophysiological responses of rat medial pontine reticular formation neurons to nicotinic activation in vitro. In response to the nicotonic agonist, 1,1-dimethyl-4-phenylpiperazinium iodine, depolarization in association with an inward current was observed in 70% of the medial pontine reticular formation neurons. This effect was insensitive to the muscarinic antagonist atropine and the nicotinic ganglionic antagonists mecamylamine and hexamethonium. However, the neuromuscular nicotinic antagonist D-tubocurare and dihydro-beta-erythroidine were effective. This is consistent with a cholinergic activation of medial pontine reticular formation neurons evoking a rapid eye movement sleep-like behavioral state, at least in part, by nicotinic receptors on these neurons.

Nonspecific excitatory effects of morphine: reverse-order precipitated withdrawal and dose-dose interactions.

We recently reported that, in naive mice pretreated with naloxone, morphine can cause withdrawal-like signs that seemingly are not mediated by "opiate" receptors. Such results were confirmed and extended here with another mouse strain. Repetitive vertical jumping could occur respective of injection sequence and depended on dose and dose ratio of the two drugs.

The mechanism of spontaneous firing in histamine neurons.

Histaminergic neurons project to virtually the whole central nervous system and display regular firing related to behavioral state. Electrophysiological studies of histaminergic neurons show that these neurons fire in a beating pacemaker pattern, which is intrinsic to individual neurons. Onset of an action potential occurs as the result of a slow depolarizing potential, which consists of voltage dependent calcium current(s) and non-inactivating sodium current. The calcium component is a voltage-dependent current activated by the return to threshold following the afterhyperpolarization (AHP) while the sodium current appears to be persistent. The action potential is followed by an AHP, which limits firing rate. The AHP is due to two potassium currents, one voltage-, the other calcium-dependent; it determines the amount of voltage-dependent currents available for activation. We show original results indicating that calcium current can be activated during AHP-like ramps and that the amount of calcium current near threshold is strongly dependent on the membrane potential and on the size of the AHP. The amount of calcium entering during the action potential will determine the duration of the AHP and thus, the firing rate.

Excitatory amino acid antagonists depress transmission in hippocampal projections to the lateral septum.

Antagonists of excitatory amino acid neurotransmission were tested as antagonists of septal excitatory postsynaptic potentials (EPSPs) generated by stimulation of the fimbria. Septal EPSPs were depressed in a concentration-dependent manner by kynurenic acid and P-bromobenzoyl piperazine-2,3-dicarboxylic acid but not by L-2-amino-4-phosphonobutyric acid or D-2-amino-5-phosphonopentanoic acid. These results indicate that the hippocampal projection to the lateral septum is similar to the Schaffer collateral system and is mediated by an excitatory amino acid or a similar derivative.

Long-term potentiation of excitatory and slow inhibitory synaptic potentials in the hippocampal-septal projection of the rat.

The hippocampal projection to the lateral septum was examined for use-dependent plasticity in a brain slice preparation using intracellular recording. Paired-pulse facilitation and posttetanic potentiation were present. Long-term potentiation (LTP) following high-frequency stimulation was observed after treatment with the GABAA antagonist bicuculline. A slow inhibitory synaptic potential also exhibited long-lasting potentiation after high-frequency stimulation. LTP of both components of the response was sensitive to NMDA antagonists.

Adenosine A1 receptor-mediated depression of corticostriatal and thalamostriatal glutamatergic synaptic potentials in vitro.

Electrophysiological recordings in rat brain slices have been used to study the actions of adenosine on striatal neurons and striatal excitatory amino acid neurotransmission originating in the cortex or the thalamus. Adenosine had no effects on membrane properties of striatal neurons. Adenosine and the A1 agonist N6-Cyclopentyl adenosine reduced EPSPs of both cortical and thalamic origin by more than 50%. Depression of EPSPs was associated with an increase in paired-pulse facilitation, suggesting a presynaptic locus of action. EPSP depression was blocked by the A1 antagonist, 8-Cyclopentyl-1,3-dipropyl xanthine. The A2 agonist 5'-(N-cyclopropyl)-carboxamidoadenosine had no effect on excitatory amino acid neurotransmission. The A1 antagonist alone enhanced the synaptic component of the evoked field potential (23 +/- 12%). These results indicate that endogenous adenosine, acting via A1 receptors, limits striatal glutamatergic neurotransmission, serving a modulatory and neuroprotective role.

Further studies on the action of baclofen on neurons of the dorsolateral septal nucleus of the rat, in vitro.

Baclofen hyperpolarizes rat dorsolateral septal neurons in a concentration-dependent manner. The apparent dissociation constant for this action is 200 nM. The baclofen-induced hyperpolarization is due to an increase in potassium conductance with a reversal potential of -88 mV. Of the various potassium and calcium channel blockers we tested, only 4-aminopyridine blocked baclofen-induced hyperpolarizations. Our results suggest that baclofen does not activate a calcium-dependent potassium conductance.