Maternal or neonatal infection: association with neonatal encephalopathy outcomes.

This corrects the article DOI: 10.1038/pr.2014.47.

Changes in overall ventricular myocardial architecture in the setting of a porcine animal model of right ventricular dilation.

BACKGROUND: Chronic pulmonary regurgitation often leads to myocardial dysfunction and heart failure. It is not fully known why secondary hypertrophy cannot fully protect against the increase in wall stress brought about by the increased end-diastolic volume in ventricular dilation. It has been assumed that mural architecture is not deranged in this situation, but we hypothesised that there might be a change in the pattern of orientation of the aggregations of cardiomyocytes, which would contribute to contractile impairment. METHODS: We created pulmonary valvular regurgitation by open chest, surgical suturing of its leaflets in seven piglets, performing sham operations in seven control animals. Using cardiovascular magnetic resonance imaging after 12 weeks of recovery, we demonstrated significantly increased right ventricular volumes in the test group. After sacrifice, diffusion tensor imaging of their hearts permitted measurement of the orientation of the cardiomyocytes. RESULTS: The helical angles in the right ventricle approached a more circumferential orientation in the setting of right ventricular RV dilation (p = 0.007), with an increased proportion of surface-parallel cardiomyocytes. In contrast, this proportion decreased in the left ventricle. Also in the left ventricle a higher proportion of E3 angles with a value around zero was found, and conversely a lower proportion of angles was found with a numerical higher value. In the dilated right ventricle the proportion of E3 angles around -90° is increased, while the proportion around 90° is decreased. CONCLUSION: Contrary to traditional views, there is a change in the orientation of both the left ventricular and right ventricular cardiomyocytes subsequent to right ventricular dilation. This will change their direction of contraction and hinder the achievement of normalisation of cardiomyocytic strain, affecting overall contractility. We suggest that the aetiology of the cardiac failure induced by right vetricular dilation may be partly explained by morphological changes in the myocardium itself.

Dopamine increases NMDA-stimulated calcium flux in striatopallidal neurons through a matrix metalloproteinase-dependent mechanism.

Dopamine (DA) is a potent neuromodulator known to influence glutamatergic transmission in striatal medium spiny neurons (MSNs). It acts on D1- and D2-like DA receptors that are expressed on two distinct subpopulations. MSNs projecting to the substantia nigra express D1 receptors (D1Rs), while those projecting to the lateral globus pallidus express D2 receptors (D2Rs). D1R signalling in particular can increase excitatory transmission through varied protein kinase A-dependent, cell-autonomous pathways. Mechanisms by which D1R signalling could increase excitatory transmission in D2R-bearing MSNs have been relatively less explored. Herein, the possibility is considered that D1R agonists increase levels of soluble factors that subsequently influence N-methyl-D-aspartate (NMDA)-stimulated calcium flux in D2R neurons. This study focuses on matrix metalloproteinases (MMPs) and MMP-generated integrin binding ligands, important soluble effectors of glutamatergic transmission that may be elevated in the setting of excess DA. It was observed that DA and a D1R agonist, SKF81297, increase MMP activity in extracts from striatal slices, as determined by cleavage of the substrate ß-dystroglycan. Using mice engineered to express the calcium indicator GCaMP3 in striatopallidal D2R-bearing neurons, it was also observed that SKF81297 pretreatment of slices (60 min) potentiates NMDA-stimulated calcium increases in this subpopulation. Effects are diminished by pretreatment with an antagonist of MMP activity or an inhibitor of integrin-dependent signalling. Together, results suggest that DA signalling can increase excitatory transmission in D2R neurons through an MMP-dependent mechanism. Future studies may be warranted to determine whether D1R-stimulated MMP-dependent processes contribute to behaviours in which increased activity in striatopallidal MSNs plays a role.

Antenatal Exposure to Magnesium Sulfate Is Associated with Reduced Cerebellar Hemorrhage in Preterm Newborns.

OBJECTIVE: To determine the association of antenatal magnesium sulfate with cerebellar hemorrhage in a prospective cohort of premature newborns evaluated by magnetic resonance imaging (MRI). STUDY DESIGN: Cross-sectional analysis of baseline characteristics from a prospective cohort of preterm newborns (<33 weeks gestation) evaluated with 3T-MRI shortly after birth. Exclusion criteria were clinical evidence of a congenital syndrome, congenital infection, or clinical status too unstable for transport to MRI. Antenatal magnesium sulfate exposure was abstracted from the medical records and the indication was classified as obstetric or neuroprotection. Two pediatric neuroradiologists, blinded to the clinical history, scored axial T2-weighted and iron susceptibility MRI sequences for cerebellar hemorrhage. The association of antenatal magnesium sulfate with cerebellar hemorrhage was evaluated using multivariable logistic regression, adjusting for postmenstrual age at MRI and known predictors of cerebellar hemorrhage. RESULTS: Cerebellar hemorrhage was present in 27 of 73 newborns (37%) imaged at a mean ± SD postmenstrual age of 32.4 ± 2 weeks. Antenatal magnesium sulfate exposure was associated with a significantly reduced risk of cerebellar hemorrhage. Adjusting for postmenstrual age at MRI, and predictors of cerebellar hemorrhage, antenatal magnesium sulfate was independently associated in our cohort with decreased cerebellar hemorrhage (OR, 0.18; 95% CI, 0.049-0.65; P = .009). CONCLUSION: Antenatal magnesium sulfate exposure is independently associated with a decreased risk of MRI-detected cerebellar hemorrhage in premature newborns, which could explain some of the reported neuroprotective effects of magnesium sulfate.

Insights from echocardiography, magnetic resonance imaging, and microcomputed tomography relative to the mid-myocardial left ventricular echogenic zone.

BACKGROUND: The anatomical substrate for the mid-mural ventricular hyperechogenic zone remains uncertain, but it may represent no more than ultrasound reflected from cardiomyocytes orientated orthogonally to the ultrasonic beam. We sought to ascertain the relationship between the echogenic zone and the orientation of the cardiomyocytes. METHODS: We used 3D echocardiography, diffusion tensor imaging, and microcomputed tomography to analyze the location and orientation of cardiomyocytes within the echogenic zone. RESULTS: We demonstrated that visualization of the echogenic zone is dependent on the position of the transducer and is most clearly seen from the apical window. Diffusion tensor imaging and microcomputed tomography show that the echogenic zone seen from the apical window corresponds to the position of the circumferentially orientated cardiomyocytes. An oblique band seen in the parasternal view relates to cardiomyocytes orientated orthogonally to the ultrasonic beam. CONCLUSIONS: The mid-mural ventricular hyperechogenic zone represents reflected ultrasound from cardiomyocytes aligned orthogonal to the ultrasonic beam. The echogenic zone does not represent a space, a connective tissue sheet, a boundary between ascending and descending limbs of a hypothetical helical ventricular myocardial band, nor an abrupt change in cardiomyocyte orientation.

Evidence for glycinergic GluN1/GluN3 NMDA receptors in hippocampal metaplasticity.

Hebbian, or associative, forms of synaptic plasticity are considered the molecular basis of learning and memory. However, associative synaptic modifications, including long-term potentiation (LTP) and depression (LTD), can form positive feedback loops which must be constrained for neural networks to remain stable. One proposed constraint mechanism is metaplasticity, a process whereby synaptic changes shift the threshold for subsequent plasticity. Metaplasticity has been functionally observed but the molecular basis is not well understood. Here, we report that stimulation which induces LTP recruits GluN2B-lacking GluN1/GluN3 NMDA receptors (NMDARs) to excitatory synapses of hippocampal pyramidal neurons. These unconventional receptors may compete against conventional GluN1/GluN2 NMDARs to favor synaptic depotentiation in response to subsequent "LTP-inducing" stimulation. These results implicate glycinergic GluN1/GluN3 NMDAR as molecular brakes on excessive synaptic strengthening, suggesting a role for these receptors in the brain that has previously been elusive.

Dopamine D2 receptors regulate collateral inhibition between striatal medium spiny neurons.

The principle neurons of the striatum are GABAergic medium spiny neurons (MSNs), whose collateral synapses onto neighboring neurons play critical roles in striatal function. MSNs can be divided by dopamine receptor expression into D1-class and D2-class MSNs, and alterations in D2 MSNs are associated with various pathological states. Despite overwhelming evidence for D2 receptors (D2Rs) in maintaining proper striatal function, it remains unclear how MSN collaterals are specifically altered by D2R activation. Here, we report that chronic D2R stimulation regulates MSN collaterals in vitro by presynaptic and postsynaptic mechanisms. We used corticostriatal cultures from mice in which MSN subtypes were distinguished by fluorophore expression. Quinpirole, an agonist for D2/3 receptors, was used to chronically activate D2Rs. Quinpirole increased the rate and strength of collateral formation onto D2R-containing MSNs as measured by dual whole-cell patch-clamp recordings. Additionally, these neurons were more sensitive to low concentrations of GABA and exhibited an increase in gephyrin puncta density, suggesting increased postsynaptic GABAA receptors. Last, quinpirole treatment increased presynaptic GABA release sites, as shown by increased frequency of sIPSCs and mIPSCs, correlating with increased VGAT (vesicular GABA transporter) puncta. Combined with the observation that there were no detectable differences in sensitivity to specific GABAA receptor modulators, we provide evidence that D2R activation powerfully transforms MSN collaterals via coordinated presynaptic and postsynaptic alterations. As the D2 class of MSNs is highly implicated in Parkinson's disease and other neurological disorders, our findings may contribute to understanding and treating the changes that occur in these pathological states.

Distinct roles for somatically and dendritically synthesized brain-derived neurotrophic factor in morphogenesis of dendritic spines.

Dendritic spines undergo the processes of formation, maturation, and pruning during development. Molecular mechanisms controlling spine maturation and pruning remain largely unknown. The gene for brain-derived neurotrophic factor (BDNF) produces two pools of mRNA, with either a short or long 3' untranslated region (3' UTR). Our previous results show that short 3' UTR Bdnf mRNA is restricted to cell bodies, whereas long 3' UTR Bdnf mRNA is also trafficked to dendrites for local translation. Mutant mice lacking long 3' UTR Bdnf mRNA display normal spines at 3 weeks of age, but thinner and denser spines in adults compared to wild-type littermates. These observations suggest that BDNF translated from long 3' UTR Bdnf mRNA, likely in dendrites, is required for spine maturation and pruning. In this study, using rat hippocampal neuronal cultures, we found that knocking down long 3' UTR Bdnf mRNA blocked spine head enlargement and spine elimination, whereas overexpressing long 3' UTR Bdnf mRNA had the opposite effect. The effect of long 3' UTR Bdnf mRNA on spine head enlargement and spine elimination was diminished by a human single-nucleotide polymorphism (SNP, rs712442) in its 3' UTR that inhibited dendritic localization of Bdnf mRNA. Furthermore, we found that overexpression of either Bdnf mRNA increased spine density at earlier time points. Spine morphological alterations were associated with corresponding changes in density, size, and function of synapses. These results indicate that somatically synthesized BDNF promotes spine formation, whereas dendritically synthesized BDNF is a key regulator of spine head growth and spine pruning.

Contrasting actions of group I metabotropic glutamate receptors in distinct mouse striatal neurones.

In mouse striatum, metabotropic glutamate receptor (mGluR) activation leads to several modulatory effects in synaptic transmission. These effects range from dampening of glutamate release from excitatory terminals to depolarization of divergent classes of interneurones. We compared the action of group I mGluR activation on several populations of striatal neurones using a combination of genetic identification, electrophysiology, and Ca(2+) imaging techniques. Patch-clamp recordings from spiny projection neurones (SPNs) and various interneurone populations demonstrated that the group I mGluR agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) robustly depolarizes several interneurone classes that form GABAergic synapses onto SPNs. We further utilized the genetic reporter mouse strain Ai38, which expresses the calcium indicator protein GCaMP3 in a Cre-dependent manner. Breeding Ai38 mice with various neurone selective, promoter-driven Cre recombinase mice resulted in GCaMP3 expression in defined cell populations in striatum. Consistent with our electrophysiological findings, group I agonist applications increased intracellular levels of calcium ([Ca(2+)]i) in all interneurone populations tested. We also found that acute DHPG application evoked a transient, rapid increase in [Ca(2+)]i from only a small percentage of identifiable SPNs. Surprisingly, this fast [Ca(2+)]i response exhibited a robust enhancement or sensitization, in a calcium-dependent fashion. Following several procedures to increase [Ca(2+)]i, the vast majority of SPNs responded with rapid changes in [Ca(2+)]i to mGluR agonists in a time-dependent fashion. These findings extend our understanding on group I mGluR influence of striatal output via powerful, local GABAergic connections in addition to [Ca(2+)]i dynamics that impact on activity or spike-timing-dependent forms of synaptic plasticity.

Maternal or neonatal infection: association with neonatal encephalopathy outcomes.

BACKGROUND: Perinatal infection may potentiate brain injury among children born preterm. The objective of this study was to examine whether maternal and/or neonatal infection are associated with adverse outcomes among term neonates with encephalopathy. METHODS: This study is a cohort study of 258 term newborns with encephalopathy whose clinical records were examined for signs of maternal infection (chorioamnionitis) and infant infection (sepsis). Multivariate regression was used to assess associations between infection, pattern, and severity of injury on neonatal magnetic resonance imaging, as well as neurodevelopment at 30 mo (neuromotor examination, or Bayley Scales of Infant Development, second edition mental development index <70 or Bayley Scales of Infant Development, third edition cognitive score <85). RESULTS: Chorioamnionitis was associated with lower risk of moderate-severe brain injury (adjusted odds ratio: 0.3; 95% confidence interval: 0.1-0.7; P = 0.004) and adverse cognitive outcome in children when compared with no chorioamnionitis. Children with signs of neonatal sepsis were more likely to exhibit watershed predominant injury than those without (P = 0.007). CONCLUSION: Among neonates with encephalopathy, chorioamnionitis was associated with a lower risk of brain injury and adverse outcomes, whereas signs of neonatal sepsis carried an elevated risk. The etiology of encephalopathy and timing of infection and its associated inflammatory response may influence whether infection potentiates or mitigates injury in term newborns.

Care practices and traditional beliefs related to neonatal jaundice in northern Vietnam: a population-based, cross-sectional descriptive study.

BACKGROUND: The National Hospital of Pediatrics in Vietnam performed >200 exchange transfusions annually (2006-08), often on infants presenting encephalopathic from lower-level hospitals. As factors delaying care-seeking are not known, we sought to study care practices and traditional beliefs relating to neonatal jaundice in northern Vietnam. METHODS: We conducted a prospective, cross-sectional, population-based, descriptive study from November 2008 through February 2010. We prospectively identified mothers of newborns through an on-going regional cohort study. Trained research assistants administered a 78-item questionnaire to mothers during home visits 14-28 days after birth except those we could not contact or whose babies remained hospitalized at 28 days. RESULTS: We enrolled 979 mothers; 99% delivered at a health facility. Infants were discharged at a median age of 1.35 days. Only 11% received jaundice education; only 27% thought jaundice could be harmful. During the first week, 77% of newborns were kept in dark rooms. Only 2.5% had routine follow-up before 14 days. Among 118 mothers who were worried by their infant's jaundice but did not seek care, 40% held non-medical beliefs about its cause or used traditional therapies instead of seeking care. Phototherapy was uncommon: 6 (0.6%) were treated before discharge and 3 (0.3%) on readmission. However, there were no exchange transfusions, kernicterus cases, or deaths. CONCLUSIONS: Early discharge without follow-up, low maternal knowledge, cultural practices, and use of traditional treatments may limit or delay detection or care-seeking for jaundice. However, in spite of the high prevalence of these practices and the low frequency of treatment, no bad outcomes were seen in this study of nearly 1,000 newborns.

Home-use icterometry in neonatal hyperbilirubinaemia: Cluster-randomised controlled trial in Vietnam.

AIM: To determine whether home-use icterometry improves parental recognition of neonatal jaundice, early care seeking and treatment to minimize risks of bilirubin encephalopathy. METHODS: Cluster-randomised controlled trial of community-level icterometry used at home by mothers in Chi Linh, Vietnam. Rural health-care workers identified and enrolled term newborns. Post-partum mothers received jaundice education and icterometry instructions and were cluster-randomised by commune. Cases received icterometers (icterometer group (IG)) and controls did not (control group (CG)). Subjects received mobile telephone calls from post-natal days 2-7 to determine maternal recognition by visual inspection and icterometer detection of jaundice (≥ 3.0 on five-point scale). Mothers without telephones, premature newborns (<35 weeks) or newborns hospitalised >5 days were excluded. RESULTS: Three hundred fifty-two subjects were enrolled (183 IG and 169 CG), of whom 11 (3.4%) were lost to telephone follow-up. Jaundice was recognised and/or detected in 94 (27%) of all newborns. Icterometry helped 11 mothers (6%) detect neonatal jaundice that was not visually recognised by IG mothers. Detection by IG mothers was not statistically greater than CG mothers (P = 0.09). Follow-up care seeking was 8% in both groups (P = 0.2), and 11% of jaundiced newborns received treatment (9% IG vs. 16% CG, P = 0.3). Newborns who received care had bilirubin measurements that averaged 257 µmol/L IG vs. 322 µmol/L CG (P = 0.3). There were no deaths. CONCLUSIONS: In this pilot study, home-use icterometry may help improve parental detection of jaundice in rural Vietnam. However, larger studies are necessary to determine the changes in recognition, care seeking and treatment.

Direct and GABA-mediated indirect effects of nicotinic ACh receptor agonists on striatal neurones.

Choline acetyltransferase-expressing interneurones (ChAT)(+) of the striatum influence the activity of medium spiny projecting neurones (MSNs) and striatal output via a disynaptic mechanism that involves GABAergic neurotransmission. Using transgenic mice that allow visual identification of MSNs and distinct populations of GABAergic interneurones expressing neuropeptide Y (NPY)(+), parvalbumin (PV)(+) and tyrosine hydroxylase (TH)(+), we further elucidate this mechanism by studying nicotinic ACh receptor (nAChR)-mediated responses. First, we determined whether striatal neurones exhibit pharmacologically induced nicotinic responses by performing patch-clamp recordings. With high [Cl(-)](i), our results showed increased spontaneous IPSC frequency and amplitude in MSNs as well as in the majority of interneurones. However, direct nAChR-mediated activity was observed in interneurones but not MSNs. In recordings with physiological [Cl(-)](i), these responses manifested as inward currents in the presence of tetrodotoxin and bicuculline methobromide. Nicotinic responses in MSNs were primarily mediated through GABA(A) receptors in feedforward inhibition. To identify the GABAergic interneurones that mediate the response, we performed dual recordings from GABAergic interneurones and MSNs. Both TH(+) and neurogliaform subtypes of NPY(+) (NPY(+) NGF) interneurones form synaptic connections with MSNs, although the strength of connectivity, response kinetics and pharmacology differ between and within the two populations. Importantly, both cell types appear to contribute to nAChR-mediated GABAergic responses in MSNs. Our data offer insight into the striatal network activity under cholinergic control, and suggest that subclasses of recently identified TH(+) and NPY(+) interneurones are key mediators of striatal nicotinic responses via GABAergic tonic and phasic currents.

Resuscitation of likely nonviable infants: a cost-utility analysis after the Born-Alive Infant Protection Act.

OBJECTIVE: The purpose of this study was to compare the effects of universal vs selective resuscitation on maternal utilities, perinatal costs, and outcomes of preterm delivery and termination of pregnancy at 20-23 weeks 6 days' gestation. STUDY DESIGN: We used studies on medical practices, prematurity outcomes, costs, and maternal utilities to construct decision-analytic models for a cohort of annual US deliveries after preterm delivery or induced termination. Outcome measures were (1) the numbers of infants who survived intact or with mild, moderate, or severe sequelae; (2) maternal quality-adjusted life years (QALYs); and (3) incremental cost-effectiveness ratios. RESULTS: Universal resuscitation of spontaneously delivered infants between 20-23 weeks 6 days' gestation increases costs by $313.1 million and decreases QALYs by 329.3 QALYs; after a termination, universal resuscitation increases costs by $15.6 million and decreases QALYs by 19.2 QALYs. With universal resuscitation, 153 more infants survive: 44 infants are intact or mildly affected; 36 infants are moderately impaired, and 73 infants are severely disabled. CONCLUSION: Selective intervention constitutes the highest utility and least costly treatment for infants at the margin of viability.

Barriers to neonatal care in developing countries: parents' and providers' perceptions.

AIM: Hospital care and advanced medical technologies for sick neonates are increasingly available, but not always readily accessible, in many countries. We characterised parents' and providers' perceptions of barriers to neonatal care in developing countries. METHODS: We interviewed parents whose infant was hospitalised within the first month of life in Cambodia, Malaysia, Laos and Vietnam, asking about perceived barriers to obtaining newborn care. We also surveyed health-care providers about perceived barriers to providing care. RESULTS: We interviewed 198 parents and 212 newborn care providers (physicians, nurses, midwives, paediatric and nursing trainees). Most families paid all costs of newborn care, which they reported as a hardship. Although newborn care is accessible, 39% reported that hospitals are too distant; almost 20% did not know where to obtain care. Parents cited lack of cleanliness (46%), poor availability of medications (42%) or services (36%), staff friendliness (42%), poor infant outcome (45%), poor communications with staff (44%) and costs of care (34%) as significant problems during prior newborn care. Providers cited lack of equipment (74%), lack of staff training (61%) and poor infrastructure (51%) as barriers to providing neonatal care. Providers identified distance to hospital, lack of transportation, care costs and low parental education as barriers for families. CONCLUSIONS: Improving cleanliness, staff friendliness and communication with parents may diminish some barriers to neonatal care in developing countries. Costs of newborn care, hospital infrastructure, distance to hospital, staffing shortages, limited staff training and limited access to medications pose more difficult barriers to remedy.

Total anomalous pulmonary venous connection: morphology and outcome from an international population-based study.

BACKGROUND: late mortality after repair of total anomalous pulmonary venous connection is frequently associated with pulmonary venous obstruction (PVO). We aimed to describe the morphological spectrum of total anomalous pulmonary venous connection and identify risk factors for death and postoperative PVO. METHODS AND RESULTS: we conducted a retrospective, international, collaborative, population-based study involving all 19 pediatric cardiac centers in the United Kingdom, Ireland, and Sweden. All infants with total anomalous pulmonary venous connection born between 1998 and 2004 were identified. Cases with functionally univentricular circulations or atrial isomerism were excluded. All available data and imaging were reviewed. Of 422 live-born cases, 205 (48.6%) had supracardiac, 110 (26.1%) had infracardiac, 67 (15.9%) had cardiac, and 37 (8.8%) had mixed connections. There were 2 cases (0.5%) of common pulmonary vein atresia. Some patients had extremely hypoplastic veins or, rarely, discrete stenosis of the individual veins. Sixty (14.2%) had associated cardiac anomalies. Sixteen died before intervention. Three-year survival for surgically treated patients was 85.2% (95% confidence interval 81.3% to 88.4%). Risk factors for death in multivariable analysis comprised earlier age at surgery, hypoplastic/stenotic pulmonary veins, associated complex cardiac lesions, postoperative pulmonary hypertension, and postoperative PVO. Sixty (14.8%) of the 406 patients undergoing total anomalous pulmonary venous connection repair had postoperative PVO that required reintervention. Three-year survival after initial surgery for patients with postoperative PVO was 58.7% (95% confidence interval 46.2% to 69.2%). Risk factors for postoperative PVO comprised preoperative hypoplastic/stenotic pulmonary veins and absence of a common confluence. CONCLUSIONS: preoperative clinical and morphological features are important risk factors for postoperative PVO and survival.

Valuation of Life With Disability: An International Comparison Study in Vietnam, Peru, and Haiti.

The authors measured perceived quality of life for 4 disabilities among 450 adults in 3 resource-limited countries, measuring mean utilities using time trade-off, and surveying participants on 35 sociocultural characteristics to compare utilities for disabilities by country and examine associated sociocultural characteristics. Mean utilities were >0 for mild and moderate, but <0 for severe and profound. Utilities differed across countries (P = .007, .000, .017, .000 for mild, moderate, severe, profound, respectively). Vietnamese utilities correlated with residence (P = .03, moderate), education (P = .03, severe), and number of children (P = .03, moderate). Peruvian utilities correlated with education (P = .05, mild; P = .05, severe), experience with disability (P = .001, mild), gender (P = .04, moderate; P = .03, profound), number of hospitalizations (P = .04, severe). In Haiti, the only correlate was rejection (P = .02, moderate). Culture-specific variables differentially shape perceptions of disability in developing countries, thereby affecting cost-effectiveness calculations. Given substantially negative perceptions, reducing major disability would improve cost-effectiveness of health-policy decisions more than reducing mortality.

High-frequency head impact causes chronic synaptic adaptation and long-term cognitive impairment in mice.

Repeated head impact exposure can cause memory and behavioral impairments. Here, we report that exposure to non-damaging, but high frequency, head impacts can alter brain function in mice through synaptic adaptation. High frequency head impact mice develop chronic cognitive impairments in the absence of traditional brain trauma pathology, and transcriptomic profiling of mouse and human chronic traumatic encephalopathy brain reveal that synapses are strongly affected by head impact. Electrophysiological analysis shows that high frequency head impacts cause chronic modification of the AMPA/NMDA ratio in neurons that underlie the changes to cognition. To demonstrate that synaptic adaptation is caused by head impact-induced glutamate release, we pretreated mice with memantine prior to head impact. Memantine prevents the development of the key transcriptomic and electrophysiological signatures of high frequency head impact, and averts cognitive dysfunction. These data reveal synapses as a target of high frequency head impact in human and mouse brain, and that this physiological adaptation in response to head impact is sufficient to induce chronic cognitive impairment in mice.

Excitatory and inhibitory synapses in neuropeptide Y-expressing striatal interneurons.

Although rare, interneurons are pivotal in governing striatal output by extensive axonal arborizations synapsing on medium spiny neurons. Using a genetically modified mouse strain in which a green fluorescent protein (GFP) is driven to be expressed under control of the neuropeptide Y (NPY) promoter, we identified NPY interneurons and compared them with striatal principal neurons. We found that the bacteria artificial chromosome (BAC)-npy mouse expresses GFP with high fidelity in the striatum to the endogenous expression of NPY. Patch-clamp analysis from NPY neurons showed a heterogeneous population of striatal interneurons. In the majority of cells, we observed spontaneous firing of action potentials in extracellular recordings. On membrane rupture, most NPY interneurons could be classified as low-threshold spiking interneurons and had high-input resistance. Voltage-clamp recordings showed that both GABA and glutamate gated ion channels mediate synaptic inputs onto these striatal interneurons. AMPA receptor-mediated spontaneous excitatory postsynaptic currents (sEPSCs) were small in amplitude and infrequent in NPY neurons. Evoked EPSCs did not show short-term plasticity but some rectification. Evoked N-methyl-d-aspartate (NMDA) EPSCs had fast decay kinetics and were poorly sensitive to an NR2B subunit containing NMDA receptor blocker. Spontaneous inhibitory postsynaptic currents (sIPSCs) were mediated by GABA(A) receptors and were quite similar among all striatal neurons studied. On the contrary, evoked IPSCs decayed faster in NPY neurons than in other striatal neurons. These data report for the first time specific properties of synaptic transmission to NPY striatal interneurons.

Left ventricular anatomy: its nomenclature, segmentation, and planes of imaging.

The American Heart Association recommends a model of the left ventricular myocardium based on 17 segments. The model is accepted and used by imagers in nuclear medicine, echocardiography, magnetic resonance imaging, and, more recently, in computed tomography. Some problems persist with the orientation and presentation of the planar imaging views between the modalities and with their registration with the segmental model. These problems would be eased if the "anterior" wall were to be called the superior wall, which is attitudinally correct. It would follow that the "anterior descending" and "posterior descending" arteries would be known as the superior and inferior interventricular arteries. This is also more correct anatomically, as is the need to describe the papillary muscles of the mitral valve as being positioned superiorly and inferiorly. In this review, we discuss these currently existing problems and make a plea for more stringent description and display of the planes used in imaging.