Image quality evaluation for a clinical organ-targeted PET camera

Introduction

A newly developed clinical organ-targeted Positron Emission Tomography (PET) system (also known as Radialis PET) is tested with a set of standardized and custom tests previously used to evaluate the performance of Positron Emission Mammography (PEM) systems.

Methods

Imaging characteristics impacting standardized uptake value (SUV) and detectability of small lesions, namely spatial resolution, linearity, uniformity, and recovery coefficients, are evaluated.

Results

In-plane spatial resolution was measured as 2.3 mm ± 0.1 mm, spatial accuracy was 0.1 mm, and uniformity measured with flood field and NEMA NU-4 phantom was 11.7% and 8.3% respectively. Selected clinical images are provided as reference to the imaging capabilities under different clinical conditions such as reduced activity of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG) and time-delayed acquisitions. SUV measurements were performed for selected clinical acquisitions to demonstrate a capability for quantitative image assessment of different types of cancer including for invasive lobular carcinoma with comparatively low metabolic activity. Quantitative imaging performance assessment with phantoms demonstrates improved contrast recovery and spill-over ratio for this PET technology when compared to other commercial organ-dedicated PET systems with similar spatial resolution. Recovery coefficients were measured to be 0.21 for the 1 mm hot rod and up to 0.89 for the 5 mm hot rod of NEMA NU-4 Image Quality phantom.

Discussion

Demonstrated ability to accurately reconstruct activity in tumors as small as 5 mm suggests that the Radialis PET technology may be well suited for emerging clinical applications such as image guided assessment of response to neoadjuvant systemic treatment (NST) in lesions smaller than 2 cm. Also, our results suggest that, while spatial resolution greatly influences the partial volume effect which degrades contrast recovery, optimized count rate performance and image reconstruction workflow may improve recovery coefficients for systems with comparable spatial resolution. We emphasize that recovery coefficient should be considered as a primary performance metric when a PET system is used for accurate lesion size or radiotracer uptake assessments.

Dispersal capacities of pollen, seeds and spores: insights from comparative analyses of spatial genetic structures in bryophytes and spermatophytes

Introduction

The dramatic fluctuations of climate conditions since the late Tertiary era have resulted in major species range shifts. These movements were conditioned by geographic barriers and species dispersal capacities. In land plants, gene flow occurs through the movement of male gametes (sperm cells, pollen grains), which carry nDNA, and diaspores (spores, seeds), which carry both cpDNA and nDNA, making them an ideal model to compare the imprints of past climate change on the spatial genetic structures of different genomic compartments. Based on a meta-analysis of cpDNA and nDNA sequence data in western Europe, we test the hypotheses that nDNA genetic structures are similar in bryophytes and spermatophytes due to the similar size of spores and pollen grains, whereas genetic structures derived from the analysis of cpDNA are significantly stronger in spermatophytes than in bryophytes due to the substantially larger size of seeds as compared to spores.

Methods

Sequence data at 1-4 loci were retrieved for 11 bryophyte and 17 spermatophyte species across their entire European range. Genetic structures between and within southern and northern populations were analyzed through F and N statistics and Mantel tests.

Results and discussion

Gst and Nst between southern and northern Europe derived from cpDNA were significantly higher, and the proportion of significant tests was higher in spermatophytes than in bryophytes. This suggests that in the latter, migrations across mountain ranges were sufficient to maintain a homogenous allelic structure across Europe, evidencing the minor role played by mountain ranges in bryophyte migrations. With nDNA, patterns of genetic structure did not significantly differ between bryophytes and spermatophytes, in line with the hypothesis that spores and pollen grains exhibit similar dispersal capacities due to their size similarity. Stronger levels of genetic differentiation between southern and northern Europe, and within southern Europe, in spermatophytes than in bryophytes, caused by higher long-distance dispersal capacities of spores as compared to seeds, may account for the strikingly higher levels of endemism in spermatophytes than in bryophytes in the Mediterranean biodiversity hotspot.

Early Diagnosis and Classification of Fetal Health Status from a Fetal Cardiotocography Dataset Using Ensemble Learning

(1) Background: According to the World Health Organization (WHO), 6.3 million intrauterine fetal deaths occur every year. The most common method of diagnosing perinatal death and taking early precautions for maternal and fetal health is a nonstress test (NST). Data on the fetal heart rate and uterus contractions from an NST device are interpreted based on a trace printer's output, allowing for a diagnosis of fetal health to be made by an expert. (2) Methods: in this study, a predictive method based on ensemble learning is proposed for the classification of fetal health (normal, suspicious, pathology) using a cardiotocography dataset of fetal movements and fetal heart rate acceleration from NST tests. (3) Results: the proposed predictor achieved an accuracy level above 99.5% on the test dataset. (4) Conclusions: from the experimental results, it was observed that a fetal health diagnosis can be made during NST using machine learning.

Antenatal fetal surveillance of women with severe obesity

OBJECTIVE

To estimate the impact of body mass index (BMI) categories on duration of the nonstress test (NST), and the need for additional tests of fetal wellbeing or interventions.

METHODS

We conducted a retrospective cohort study of women with singleton pregnancies who had an NST for the indications of severe obesity (BMI ≥40 kg/m²), diabetes (pre-gestational or gestational), hypertensive disorders (chronic, gestational, and preeclampsia), and others between 1 January 2015 until 31 December 2016. NST durations (<30 and ≥30 min) were compared between groups first based on BMI (kg/m²) categories (<30, 30-39, 40-49, and ≥50) and then based on BMI and comorbidities: (1) severe obesity alone, (2) severe obesity and comorbidities, and (3) comorbidities alone. We compared the results of the NSTs, any subsequent fetal testing or interventions, and pregnancy outcomes among groups. Demographic information was compared using t-tests for continuous data and χ² analyses or Fisher's exact test, if the cells sizes were small, for categorical data. NST durations based on BMI groups, as well as BMI and comorbidities groups, were compared using linear mixed models and ANOVA.

RESULTS

Three hundred and fifty-one women underwent 1665 NSTs during the study period. After excluding women <18 and >50 years, gestational age <30 weeks, fetal anomalies, and NSTs lasting longer than 60 min, the study population included 313 women and 1471 NSTs. The mean NST duration in minutes of the BMI ≥50 (32.2 ± 9.6) category was significantly longer than the NST duration of the other BMI categories (BMI <30: 29.4 ± 8.3; BMI 30-39: 29.7 ± 8.9; BMI 40-49: 29.9 ± 8.3) (p=.05). Additionally, there was an increased percentage of NSTs lasting ≥30 min as the BMI category increased (p=.005). Women in the severe obesity and comorbidities group (n = 79) were less likely to have a reactive NST than women with severe obesity alone (n = 56) or comorbidities alone (n = 178) (92% vs. 97% vs. 98%, p<.0001). They were also more likely to need a biophysical profile (BPP) (8% vs. 3% vs. 2%, p<.0001). Of the 25 women that were sent to the labor and delivery unit for evaluation, 20 (80%) were admitted and delivered. The reasons for delivery were hypertension (n = 9, 45%), an abnormal NST (n = 5, 25%), oligohydramnios (n = 4, 20%), and labor (n = 2, 10%).

CONCLUSIONS

We found an increase in NST duration as the BMI increased. Women with severe obesity and a comorbidity were more likely to have a nonreactive NST and require a subsequent BPP. Of the 20 patients delivered due to NST surveillance, the most common indication for delivery was hypertension.

Target-specific projections of amygdala somatostatin-expressing neurons to the hypothalamus and brainstem

Somatostatin neurons in the central nucleus of the amygdala (CeA/Sst) can be parsed into subpopulations that project either to the nucleus of the solitary tract (NST) or parabrachial nucleus (PBN). We have shown recently that inhibition of CeA/Sst-to-NST neurons increased the ingestion of a normally aversive taste stimulus, quinine HCl (QHCl). Because the CeA innervates other forebrain areas such as the lateral hypothalamus (LH) that also sends axonal projections to the NST, the effects on QHCl intake could be, in part, the result of CeA modulation of LH-to-NST neurons. To address these issues, the present study investigated whether CeA/Sst-to-NST neurons are distinct from CeA/Sst-to-LH neurons. For comparison purposes, additional experiments assessed divergent innervation of the LH by CeA/Sst-to-PBN neurons. In Sst-cre mice, two different retrograde transported flox viruses were injected into the NST and the ipsilateral LH or PBN and ipsilateral LH. The results showed that 90% or more of retrograde-labeled CeA/Sst neurons project either to the LH, NST, or PBN. Separate populations of CeA/Sst neurons projecting to these different regions suggest a highly heterogeneous population in terms of synaptic target and likely function.

Functional Analysis of Poplar Sombrero-Type NAC Transcription Factors Yields a Strategy to Modify Woody Cell Wall Properties

Woody cells generate lignocellulosic biomass, which is a promising sustainable bioresource for wide industrial applications. Woody cell differentiation in vascular plants, including the model plant poplar (Populus trichocarpa), is regulated by a set of NAC family transcription factors, the VASCULAR-RELATED NAC-DOMAIN (VND), NAC SECONDARY CELL WALL THICKENING PROMOTING FACTOR (NST)/SND, and SOMBRERO (SMB) (VNS)-related proteins, but the precise contributions of each VNS protein to wood quality are unknown. Here, we performed a detailed functional analysis of the poplar SMB-type VNS proteins PtVNS13-PtVNS16. PtVNS13-PtVNS16 were preferentially expressed in the roots of young poplar plantlets, similar to the Arabidopsis thalianaSMB gene. PtVNS13 and PtVNS14, as well as the NST-type PtVNS11, suppressed the abnormal root cap phenotype of the Arabidopsis sombrero-3 mutant, whereas the VND-type PtVNS07 gene did not, suggesting a functional gap between SMB- or NST-type VNS proteins and VND-type VNS proteins. Overexpressing PtVNS13-PtVNS16 in Arabidopsis seedlings and poplar leaves induced ectopic xylem-vessel-like cells with secondary wall deposition, and a transient expression assay showed that PtVNS13-16 transactivated woody-cell-related genes. Interestingly, although any VNS protein rescued the pendant stem phenotype of the Arabidopsis nst1-1 nst3-1 mutant, the resulting inflorescence stems exhibited distinct cell wall properties: poplar VNS genes generated woody cell walls with higher enzymatic saccharification efficiencies compared with Arabidopsis VNS genes. Together, our data reveal clear functional diversity among VNS proteins in woody cell differentiation and demonstrate a novel VNS-based strategy for modifying woody cell wall properties toward enhanced utilization of woody biomass.

BoSL FAL pump: A small, low-cost, easily constructed, 3D-printed peristaltic pump for sampling of waters

Water sampling is an essential undertaking for water utilities and agencies to protect and enhance our natural resources. The high variability in water quality, however, often necessitates a spatially distributed sampling program which is impeded by high-cost and large sampling devices. This paper presents the BoSL FAL Pump - a low-cost, easily constructed, 3D-printed peristaltic pump which can be made from commonly available components and is sized to suit even the most space constrained installations. The pump is 38 mm in height and 28 mm in diameter, its components cost $19 AUD and the construction time is just 12 min (excluding 3D printing times). The pump is driven by a direct current motor which is commonly available, cheap and allows for flexibility in the energy supply (5-12 V). Optionally, the pump has a Hall effect sensor and magnet to detect rotation rates and pumping volumes to improve the accuracy of pumping rates/volumes. The pump can be easily controlled by commonly available microcontrollers, as demonstrated by this paper which implements the ATmega328P on the Arduino Uno R3. This paper validates the pump for long-term deployments at flow rates of up to 13 mL per minute in 0.14 mL volume increments at accuracy levels of greater than 99%. The pump itself is scalable, allowing for a wider range of pumping rates when, for example, large volume samples are required for pathogen and micropollutant detection.

Distinct Populations of Amygdala Somatostatin-Expressing Neurons Project to the Nucleus of the Solitary Tract and Parabrachial Nucleus

Rostral forebrain structures, such as the central nucleus of the amygdala (CeA), send projections to the nucleus of the solitary tract (NST) and the parabrachial nucleus (PBN) that modulate taste-elicited responses. However, the proportion of forebrain-induced excitatory and inhibitory effects often differs when taste cell recording changes from the NST to the PBN. The present study investigated whether this descending influence might originate from a shared or distinct population of neurons marked by expression of somatostatin (Sst). In Sst-reporter mice, the retrograde tracers' cholera toxin subunit B AlexaFluor-488 and -647 conjugates were injected into the taste-responsive regions of the NST and the ipsilateral PBN. In Sst-cre mice, the cre-dependent retrograde tracers' enhanced yellow fluorescent protein Herpes Simplex Virus (HSV) and mCherry fluorescent protein HSV were injected into the NST and the ipsilateral PBN. The results showed that ~40% of CeA-to-PBN neurons expressed Sst compared with ~ 23% of CeA-to-NST neurons. For both the CeA Sst-positive and -negative populations, the vast majority projected to the NST or PBN but not both nuclei. Thus, a subset of CeA-to-NST and CeA-to-PBN neurons are marked by Sst expression and are largely distinct from one another. Separate populations of CeA/Sst neurons projecting to the NST and PBN suggest that differential modulation of taste processing might, in part, rely on differences in local brainstem/forebrain synaptic connections.

Endocrinology of thermoregulation in birds in a changing climate

The ability to maintain a (relatively) stable body temperature in a wide range of thermal environments by use of endogenous heat production is a unique feature of endotherms such as birds. Endothermy is acquired and regulated via various endocrine and molecular pathways, and ultimately allows wide aerial, aquatic, and terrestrial distribution in variable environments. However, due to our changing climate, birds are faced with potential new challenges for thermoregulation, such as more frequent extreme weather events, lower predictability of climate, and increasing mean temperature. We provide an overview on thermoregulation in birds and its endocrine and molecular mechanisms, pinpointing gaps in current knowledge and recent developments, focusing especially on non-model species to understand the generality of, and variation in, mechanisms. We highlight plasticity of thermoregulation and underlying endocrine regulation, because thorough understanding of plasticity is key to predicting responses to changing environmental conditions. To this end, we discuss how changing climate is likely to affect avian thermoregulation and associated endocrine traits, and how the interplay between these physiological processes may play a role in facilitating or constraining adaptation to a changing climate. We conclude that while the general patterns of endocrine regulation of thermogenesis are quite well understood, at least in poultry, the molecular and endocrine mechanisms that regulate, e.g. mitochondrial function and plasticity of thermoregulation over different time scales (from transgenerational to daily variation), need to be unveiled. Plasticity may ameliorate climate change effects on thermoregulation to some extent, but the increased frequency of extreme weather events, and associated changes in resource availability, may be beyond the scope and/or speed for plastic responses. This could lead to selection for more tolerant phenotypes, if the underlying physiological traits harbour genetic and individual variation for selection to act on - a key question for future research.

Electrophysiological responses to sugars and amino acids in the nucleus of the solitary tract of type 1 taste receptor double-knockout mice

Strong evidence supports a major role for heterodimers of the type 1 taste receptor (T1R) family in the taste transduction of sugars (T1R2+T1R3) and amino acids (T1R1+T1R3), but there are also neural and behavioral data supporting T1R-independent mechanisms. Most neural evidence for alternate mechanisms comes from whole nerve recordings in mice with deletion of a single T1R family member, limiting conclusions about the functional significance and T1R independence of the remaining responses. To clarify these issues, we recorded single-unit taste responses from the nucleus of the solitary tract in T1R double-knockout (double-KO) mice lacking functional T1R1+T1R3 [KO1+3] or T1R2+T1R3 [KO2+3] receptors and their wild-type background strains [WT; C57BL/6J (B6), 129X1/SvJ (S129)]. In both double-KO strains, responses to sugars and a moderate concentration of an monosodium glutamate + amiloride + inosine 5'-monophosphate cocktail (0.1 M, i.e., umami) were profoundly depressed, whereas a panel of 0.6 M amino acids were mostly unaffected. Strikingly, in contrast to WT mice, no double-KO neurons responded selectively to sugars and umami, precluding segregation of this group of stimuli from those representing other taste qualities in a multidimensional scaling analysis. Nevertheless, residual sugar responses, mainly elicited by monosaccharides, persisted as small "sideband" responses in double-KOs. Thus other receptors may convey limited information about sugars to the central nervous system, but T1Rs appear critical for coding the distinct perceptual features of sugar and umami stimuli. The persistence of amino acid responses supports previous proposals of alternate receptors, but because these stimuli affected multiple neuron types, further investigations are necessary.NEW & NOTEWORTHY The type 1 taste receptor (T1R) family is crucial for transducing sugars and amino acids, but there is evidence for T1R-independent mechanisms. In this study, single-unit recordings from the nucleus of the solitary tract in T1R double-knockout mice lacking T1R1+T1R3 or T1R2+T1R3 receptors revealed greatly reduced umami synergism and sugar responses. Nevertheless, residual sugar responses persisted, mainly elicited by monosaccharides and evident as "sidebands" in neurons activated more vigorously by other qualities.

Evolutionary Genetics of Hypoxia and Cold Tolerance in Mammals

Low oxygen and fluctuant ambient temperature pose serious challenges to mammalian survival. Physiological adaptations in mammals to hypoxia and low temperatures have been intensively investigated, yet their underlying molecular mechanisms need further exploration. Independent invasions of high-altitude plateaus, subterranean burrows and marine environments by different mammals provide opportunities to conduct such analyses. Here, we focused on six genes in the hypoxia inducible factor (HIF) pathway and two non-shivering thermogenesis (NST)-related genes [PPAR co-activator 1 (PGC-1) and uncoupling protein 1 (UCP1)] in representative species of pikas and other mammals to understand whether these loci were targeted by natural selection during independent invasions to conditions characterized by hypoxia and temperature fluctuations by high-altitude, subterranean and marine mammals. Our analyses revealed pervasive positive selection signals in the HIF pathway genes of mammals occupying high-altitude, subterranean and aquatic ecosystems; however, the mechanisms underlying their independent adaptations to hypoxic environments varied by taxa, since different genes were positively selected in each taxon and expression levels of individual genes varied among species. Additionally, parallel amino acid substitutions were also detected in hypoxia-tolerant mammals, indicating that convergent evolution may play a role in their independent adaptations to hypoxic environments. However, divergent evolutionary histories of NST-related genes were noted, since significant evidence of positive selection was observed in PGC-1 and UCP1 in high-altitude species and subterranean rodents; however, UCP1 may have already lost its function in diving cetaceans, which may be related to the thick blubber layer of adipose and connective tissue in these mammals.

State-trait anxiety levels during pregnancy and foetal parameters following intervention with music therapy

BACKGROUND

Research indicates that anxiety during pregnancy may be a risk factor for the development of alterations in the mental health of the pregnant woman and of obstetric complications.

OBJECTIVE

to investigate the effect of music therapy on maternal anxiety, before and after a non-stress test (NST), and the effect of maternal anxiety on the birthing process and birth size.

METHODS

409 nulliparous women coming for routine prenatal care were randomized in the third trimester to receive either music therapy (n = 204) or no music therapy (n = 205) during an NST. Maternal anxiety was assessed using the Spielberger State-Trait Anxiety Inventory before and after the NST.

RESULTS

After the NST, the women from the music group showed significantly lower scores in state anxiety (OR = 0.87; p < 0.001) as well as trait anxiety (p < 0.001) than the control group. Furthermore, the pregnant women from the music group presented lower levels of state-trait anxiety than the control group in relation to the variables of birth process, and higher birth weight and chest circumference in the newborn (OR = 3.5 and OR = 0.81, respectively; p < 0.05).

LIMITATIONS

This study was limited by the fact that it was a single-centre study; the observers conducting the NST were not blinded to the allocation, although neither midwife had any knowledge of the maternal anxiety scores, and we could not apply the double-blind method due to the nature of the observation.

CONCLUSIONS

Our findings confirm that music therapy intervention during pregnancy could reduce elevated state-trait anxiety levels during the third trimester. Further research into the influence of music therapy as intervention on maternal anxiety and on the birthing process and birth size is required during pregnancy.

Effects of prenatal music stimulation on state/trait anxiety in full-term pregnancy and its influence on childbirth: a randomized controlled trial

BACKGROUND

Many researchers have pointed out the strong relationship between maternal psychological well-being and fetal welfare during pregnancy. The impact of music interventions during pregnancy should be examined in depth, as they could have an impact on stress reduction, not only during pregnancy but also during the course of delivery, and furthermore induce fetal awareness.

OBJECTIVE

This study aimed to investigate the effect of music on maternal anxiety, before and after a non-stress test (NST), and the effect of music on the birthing process.

MATERIAL AND METHOD

The four hundred and nine pregnant women coming for routine prenatal care were randomized in the third trimester to receive either music (n = 204) or no music (n = 205) stimulation during an NST. The primary outcome was considered as the maternal state anxiety score before and after the NST, and the secondary outcome was the birthing process.

RESULTS

Before their NST, full-term pregnant women who had received music intervention were found to have a similar state-trait anxiety score to those from the control group, with 38.10 ± 8.8 and 38.08 ± 8.2, respectively (p = .97). After the NST, the mean state-trait anxiety score of each group was recorded, with results of 30.58 ± 13.2 for those with music intervention, and 43.11 ± 15.0 for those without music intervention (p < .001). In the control group, the NST was followed by a statistically significant increase in the state-trait anxiety score (38.08 ± 8.2 versus 43.11 ± 15.0, p < .001). However, listening to music during the NST resulted in a statistically significant decrease in the state-trait anxiety score of the study group (38.10 ± 8.8 versus 30.58 ± 13.2, OR = 0.87, p < .001). Furthermore, the first stage of labor was shorter in women who received music stimulation (OR = 0.92, p < .004). They also presented a more natural delivery beginning (spontaneous) and less medication (stimulated and induced) than those who were not stimulated musically, with statistically significant differences (p < .01).

CONCLUSIONS

Prenatal music intervention could be a useful and effective tool to reduce anxiety in full-term pregnant women during an NST and improve the delivery process by reducing the first stage of labor in nulliparous women.

Disruption of re-intake after partial withdrawal of gastric food contents in rats lesioned in the gelatinous part of the nucleus of the solitary tract

Sensory information from the upper gastrointestinal tract is critical in food intake regulation. Signals from different levels of the digestive system are processed to the brain, among other systems, via the vagus nerve, which mainly projects towards the nucleus of the solitary tract (NST). The objective of this study was to analyze the participation of the gelatinous part (SolG) of the NST in short-term food intake. One-third of the stomach food content was withdrawn at 5 min after the end of a meal, and food was then available ad libitum for different time periods. SolG-lesioned and control animals ingested a similar amount of the initial liquid meal, but the former consumed significantly smaller amounts and failed to compensate for the food deficit, whereas the controls re-ingested virtually the same amount as extracted. These data suggest that the SolG, as in the case of related anatomical structures such as the vagus nerve or external lateral parabrachial subnucleus, may be relevant in particular circumstances that require the rapid processing of vagal-related food intake adjustment associated to the upper gastrointestinal tract.

Endoplasmic reticulum: Where nucleotide sugar transport meets cytokinin control mechanisms

The endoplasmic reticulum (ER) is a multifunctional eukaryotic organelle where the vast majority of secretory proteins are folded and assembled to achieve their correct tertiary structures. The lumen of the ER and Golgi apparatus also provides an environment for numerous glycosylation reactions essential for modifications of proteins and lipids, and for cell wall biosynthesis. These glycosylation reactions require a constant supply of cytosolically synthesized substrate precursors, nucleotide sugars, which are transported by a group of dedicated nucleotide sugar transporters (NST). Recently, we have reported on the identification of a novel ER-localized NST protein, ROCK1, which mediates the transport of UDP-linked acetylated hexosamines across the ER membrane in Arabidopsis. Interestingly, it has been demonstrated that the activity of ROCK1 is important for the regulation of cytokinin-degrading enzymes, cytokinin oxidases/dehydrogenases (CKX), in the ER and, thus, for cytokinin responses. In this addendum we will address the biochemical and cellular activity of the ROCK1 transporter and its phylogenetic relation to other NST proteins.

NMDA receptors control vagal afferent excitability in the nucleus of the solitary tract

Previous behavioral studies have demonstrated that presynaptic N-methyl-d-aspartate (NMDA) receptors expressed on vagal afferent terminals are involved in food intake and satiety. Therefore, using in vitro live cell calcium imaging of prelabeled rat hindbrain slices, we characterized which NMDA receptor GluN2 subunits may regulate vagal afferent activity. The nonselective NMDA receptor antagonist d,l-2-amino-5-phosphonopentanoic acid (d,l-AP5) significantly inhibited vagal terminal calcium influx, while the excitatory amino acid reuptake inhibitor d,l-threo-β-benzyloxyaspartic acid (TBOA), significantly increased terminal calcium levels following pharmacological stimulation with ATP. Subunit-specific NMDA receptor antagonists and potentiators were used to identify which GluN2 subunits mediate the NMDA receptor response on the vagal afferent terminals. The GluN2B-selective antagonist, ifenprodil, selectively reduced vagal calcium influx with stimulation compared to the time control. The GluN2A-selective antagonist, 3-chloro-4-fluoro-N-[4-[[2-(phenylcarbonyl)hydrazino]carbonyl] benzyl]benzenesulfonamide (TCN 201) produced smaller but not statistically significant effects. Furthermore, the GluN2A/B-selective potentiator (pregnenolone sulfate) and the GluN2C/D-selective potentiator [(3-chlorophenyl)(6,7-dimethoxy-1-((4-methoxyphenoxy)methyl)-3,4-dihydroisoquinolin-2(1H)-yl)methanone; (CIQ)] enhanced vagal afferent calcium influx during stimulation. These data suggest that presynaptic NMDA receptors with GluN2B, GluN2C, and GluN2D subunits may predominantly control vagal afferent excitability in the nucleus of the solitary tract.

Artemisia santolinifolia enhances glutamatergic neurotransmission in the nucleus of the solitary tract

Artemisia extracts have been used as remedies for a variety of maladies related to metabolic and gastrointestinal control. Because the vagal afferent-nucleus of the solitary tract (NST) synapse regulates the same homeostatic functions affected by Artemisia, it is possible that these extracts may have activity at the synaptic level in the NST. Therefore, we evaluated how extracts of three common medicinal Artemisia species, Artemisia santolinifolia (SANT), Artemisia scoparia (SCO), and Artemisia dracunculus L (PMI-5011), modulate the excitability of the glutamatergic vagal afferent-NST synapse. Our in vitro live cell calcium imaging data from prelabeled vagal afferent terminals show that SANT extract is a positive modulator of vagal afferent calcium levels, as the extract significantly increased the calcium signal relative to the time control. Neither SCO nor PMI-5011 extract altered the vagal calcium signals compared to the time control. Furthermore, whole cell voltage-clamp recordings from NST neurons corroborated the vagal terminal calcium data in that SANT extract also significantly increased miniature excitatory postsynaptic current (mEPSC) frequency in NST neurons. These data suggest that SANT extract could be a pharmacologically significant mediator of glutamatergic neurotransmission within the CNS.

St. John's Wort enhances the synaptic activity of the nucleus of the solitary tract

OBJECTIVE

St. John's Wort (SJW) extract, which is commonly used to treat depression, inhibits the reuptake of several neurotransmitters, including glutamate, serotonin, norepinephrine, and dopamine. Glutamatergic visceral vagal afferents synapse upon neurons of the solitary tract (NST); thus, the aim of this study was to evaluate whether SJW extract modulates glutamatergic neurotransmission within the NST.

METHODS

We used live cell calcium imaging to evaluate whether SJW and its isolated components hypericin and hyperforin increase the excitability of prelabeled vagal afferent terminals synapsing upon the NST. We used voltage-clamp recordings of spontaneous miniature excitatory postsynaptic currents (mEPSCs) to evaluate whether SJW alters glutamate release from vagal afferents onto NST neurons.

RESULTS

Our imaging data show that SJW (50 μg/mL) increased the intracellular calcium levels of stimulated vagal afferent terminals compared with the bath control. This increase in presynaptic vagal afferent calcium by the extract coincides with an increase in neurotransmitter release within the nucleus of the solitary tract, as the frequency of mEPSCs is significantly higher in the presence of the extract compared with the control. Finally, our imaging data show that hyperforin, a known component of SJW extract, also significantly increases terminal calcium levels.

CONCLUSION

These data suggest that SJW extract can significantly increase the probability of glutamate release from vagal afferents onto the NST by increasing presynaptic calcium. The in vitro vagal afferent synapse with NST neurons is an ideal model system to examine the mechanism of action of botanical agents on glutamatergic neurotransmission.