Hippocampal LTP and contextual learning require surface diffusion of AMPA receptors.

Long-term potentiation (LTP) of excitatory synaptic transmission has long been considered a cellular correlate for learning and memory. Early LTP (less than 1 h) had initially been explained either by presynaptic increases in glutamate release or by direct modification of postsynaptic AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor function. Compelling models have more recently proposed that synaptic potentiation can occur by the recruitment of additional postsynaptic AMPA receptors (AMPARs), sourced either from an intracellular reserve pool by exocytosis or from nearby extra-synaptic receptors pre-existing on the neuronal surface. However, the exact mechanism through which synapses can rapidly recruit new AMPARs during early LTP remains unknown. In particular, direct evidence for a pivotal role of AMPAR surface diffusion as a trafficking mechanism in synaptic plasticity is still lacking. Here, using AMPAR immobilization approaches, we show that interfering with AMPAR surface diffusion markedly impairs synaptic potentiation of Schaffer collaterals and commissural inputs to the CA1 area of the mouse hippocampus in cultured slices, acute slices and in vivo. Our data also identify distinct contributions of various AMPAR trafficking routes to the temporal profile of synaptic potentiation. In addition, AMPAR immobilization in vivo in the dorsal hippocampus inhibited fear conditioning, indicating that AMPAR diffusion is important for the early phase of contextual learning. Therefore, our results provide a direct demonstration that the recruitment of new receptors to synapses by surface diffusion is a critical mechanism for the expression of LTP and hippocampal learning. Since AMPAR surface diffusion is dictated by weak Brownian forces that are readily perturbed by protein-protein interactions, we anticipate that this fundamental trafficking mechanism will be a key target for modulating synaptic potentiation and learning.

Charge Transfer and Built-in Electric Fields between a Crystalline Oxide and Silicon.

We report charge transfer and built-in electric fields across the epitaxial SrNb_{x}Ti_{1-x}O_{3-δ}/Si(001) interface. Electrical transport measurements indicate the formation of a hole gas in the Si and the presence of built-in fields. Hard x-ray photoelectron measurements reveal pronounced asymmetries in core-level spectra that arise from these built-in fields. Theoretical analysis of core-level spectra enables built-in fields and the resulting band bending to be spatially mapped across the heterojunction. The demonstration of tunable charge transfer, built-in fields, and the spatial mapping of the latter, lays the groundwork for the development of electrically coupled, functional heterojunctions.

Incomplete lung recovery following sub-acute inhalation of combustion-derived ultrafine particles in mice.

BACKGROUND: Particulate matter (PM) is one of the six criteria pollutant classes for which National Ambient Air Quality Standards have been set by the United States Environmental Protection Agency. Exposures to PM have been correlated with increased cardio-pulmonary morbidity and mortality. Butadiene soot (BDS), generated from the incomplete combustion of 1,3-butadiene (BD), is both a model PM mixture and a real-life example of a petrochemical product of incomplete combustion. There are numerous events, including wildfires, accidents at refineries and tank car explosions that result in sub-acute exposure to high levels of airborne particles, with the people exposed facing serious health problems. These real-life events highlight the need to investigate the health effects induced by short-term exposure to elevated levels of PM, as well as to assess whether, and if so, how well these adverse effects are resolved over time. In the present study, we investigated the extent of recovery of mouse lungs 10 days after inhalation exposures to environmentally-relevant levels of BDS aerosols had ended. METHODS: Female BALB/c mice exposed to either HEPA-filtered air or to BDS (5 mg/m(3) in HEPA filtered air, 4 h/day, 21 consecutive days) were sacrificed immediately, or 10 days after the final BDS exposure. Bronchoalveolar lavage fluid (BALF) was collected for cytology and cytokine analysis. Lung proteins and RNA were extracted for protein and gene expression analysis. Lung histopathology evaluation also was performed. RESULTS: Sub-acute exposures of mice to hydrocarbon-rich ultrafine particles induced: (1) BALF neutrophil elevation; (2) lung mucosal inflammation, and (3) increased BALF IL-1ß concentration; with all three outcomes returning to baseline levels 10 days post-exposure. In contrast, (4) lung connective tissue inflammation persisted 10 days post-exposure; (5) we detected time-dependent up-regulation of biotransformation and oxidative stress genes, with incomplete return to baseline levels; and (6) we observed persistent particle alveolar load following 10 days of recovery. CONCLUSION: These data show that 10 days after a 21-day exposure to 5 mg/m(3) of BDS has ended, incomplete lung recovery promotes a pro-biotransformation, pro-oxidant, and pro-inflammatory milieu, which may be a starting point for potential long-term cardio-pulmonary effects.

The experience of mothers caring for a child with a brain tumour.

BACKGROUND: Brain tumours are the second most common form of childhood cancer, accounting for over 20% of all cases in European children. Understanding the impact of diagnosis and treatment of a brain tumour on the family is an essential pre-requisite to identifying ways to provide effective support. AIM: (1) To explore the impact of having a child with a brain tumour on the main caregiver in the family; (2) to describe mothers' experiences of coping with their child's illness, including personal barriers and strengths; and (3) to identify causes of stress and sources of support to inform improvements in care delivery. METHOD: Participants were drawn from a group of caregivers enrolled in a longitudinal study of outcome following diagnosis of a childhood brain tumour. Six caregivers took part, two from each of the high-, medium- and low-impact groups based on their Impact on Families Scale scores. Semi-structured interviews were used, with questions covering: (1) impact of the diagnosis on main caregiver and family; (2) personal barriers and strengths; and (3) causes of stress and sources of support. Interviews were transcribed verbatim and coded manually into five themes, which comprised 19 subthemes. FINDINGS: Coping methods and provision of help and support were major preoccupations for main caregivers from all impact groups. Caregivers in the high-impact group reported less conflict. High- and medium-impact group caregivers had experienced less 'hindrance and heartache', than those with low impact scores, suggesting that the stress associated with diagnosis and treatment of the tumour may have increased cohesion and acceptance within these families. CONCLUSION: Families of children diagnosed with a brain tumour experience considerable negative impact and may perceive themselves as struggling to cope. Provision of help and support, within and outside the extended family, including from health, education and other services, is perceived as helpful.

A microdeletion in cytochrome c oxidase (COX) subunit III associated with COX deficiency and recurrent myoglobinuria.

We have identified a 15-bp microdeletion in a highly conserved region of the mitochondrially encoded gene for cytochrome c oxidase (COX) subunit III in a patient with severe isolated COX deficiency and recurrent myoglobinuria. The mutant mitochondrial DNA (mtDNA) comprised 92% of the mtDNA in muscle and 0.7% in leukocytes. Immunoblots and immunocytochemistry suggested a lack of assembly or instability of the complex. Microdissected muscle fibres revealed significantly higher portions of mutant mtDNA in COX-negative than in COX-positive fibres. This represents the first case of isolated COX deficiency to be defined at the molecular level.

COVID-19 Vaccine Acceptance Among Latino/a Immigrants: The Role of Collective Responsibility and Confidence.

Research on COVID-19 vaccine hesitancy has been sparse among Latino/a immigrants, a population at high risk for infection. This exploratory study examines rates of vaccine acceptance and its association with psychological antecedents of vaccination among Latino/a immigrants. A cross-sectional telephone survey on perceptions of COVID-19 was administered between October 2020 to February 2021 in South Florida to 200 adult Latino/a immigrants. Descriptive statistics, bivariate analysis, and logistic regression were employed to determine the influence of independent variables on vaccine acceptance. Most participants indicated a willingness to get vaccinated. Participants with higher confidence (aOR = 10.2, 95% CI: 4.8-21.8) and collective responsibility scores were (aOR = 3.1, 95%CI:1.3-6.9) more likely to report vaccine acceptance than those with lower scores. No other psychological antecedents or demographic variables were significantly associated with vaccine acceptance. Study results provide insights into motivating factors for vaccination that can inform culturally tailored education campaigns to increase vaccine acceptability in this population.

Placental contribution to neonatal encephalopathy.

Placental assessment, although currently underused, can inform our understanding of the etiology and timing of Neonatal Encephalopathy (NE). We review our current understanding of the links between placental dysfunction and NE and how this information may inform clinical decisions, now and in the future, emphasizing the four major placental lesions associated with NE. In addition, we discuss maternal and fetal factors that are hypothesized to contribute to specific placental pathologies, especially innate or acquired thrombophilias. We outline the importance of assessing placenta across trimesters and after delivery. As this field continues to evolve, currently available placental histopathological examination methods may need to be combined with advanced prenatal molecular and imaging assessments of placenta and be applied in well-designed studies in large representative populations to better define the links between placental dysfunction and NE.

Exposure to bisphenol A differentially impacts neurodevelopment and behavior in Drosophila melanogaster from distinct genetic backgrounds.

Bisphenol A (BPA) is a ubiquitous environmental chemical that has been linked to behavioral differences in children and shown to impact critical neurodevelopmental processes in animal models. Though data is emerging, we still have an incomplete picture of how BPA disrupts neurodevelopment; in particular, how its impacts may vary across different genetic backgrounds. Given the genetic tractability of Drosophila melanogaster, they present a valuable model to address this question. Fruit flies are increasingly being used for assessment of neurotoxicants because of their relatively simple brain structure and variety of measurable behaviors. Here we investigated the neurodevelopmental impacts of BPA across two genetic strains of Drosophila-w1118 (control) and the Fragile X Syndrome (FXS) model-by examining both behavioral and neuronal phenotypes. We show that BPA induces hyperactivity in larvae, increases repetitive grooming behavior in adults, reduces courtship behavior, impairs axon guidance in the mushroom body, and disrupts neural stem cell development in the w1118 genetic strain. Remarkably, for every behavioral and neuronal phenotype examined, the impact of BPA in FXS flies was either insignificant or contrasted with the phenotypes observed in the w1118 strain. This data indicates that the neurodevelopmental impacts of BPA can vary widely depending on genetic background and suggests BPA may elicit a gene-environment interaction with Drosophila fragile X mental retardation 1 (dFmr1)-the ortholog of human FMR1, which causes Fragile X Syndrome and is associated with autism spectrum disorder.

Link between packing morphology and the distribution of contact forces and stresses in packings of highly nonconvex particles.

An external load on a particle packing is distributed internally through a heterogeneous network of particle contacts. This contact force distribution determines the stability of the particle packing and the resulting structure. Here, we investigate the homogeneity of the contact force distribution in packings of highly nonconvex particles both in two-dimensional (2D) and three-dimensional (3D) packings. A recently developed discrete element method is used to model packings of nonconvex particles of varying sphericity. Our results establish that in 3D packings the distribution of the contact forces in the normal direction becomes increasingly heterogeneous with decreasing particle sphericity. However, in 2D packings the contact force distribution is independent of particle sphericity, indicating that results obtained in 2D packings cannot be extrapolated readily to 3D packings. Radial distribution functions show that the crystallinity in 3D packings decreases with decreasing particle sphericity. We link the decreasing homogeneity of the contact force distributions to the decreasing crystallinity of 3D packings. These findings are complementary to the previously observed link between the heterogeneity of the contact force distribution and a decreasing packing crystallinity due to an increasing polydispersity of spherical particles.

Competition in retinogeniculate patterning driven by spontaneous activity.

When contacts are first forming in the developing nervous system, many neurons generate spontaneous activity that has been hypothesized to shape appropriately patterned connections. In Mustela putorius furo, monocular intraocular blockade of spontaneous retinal waves of action potentials by cholinergic agents altered the subsequent eye-specific lamination pattern of the lateral geniculate nucleus (LGN). The projection from the active retina was greatly expanded into territory normally belonging to the other eye, and the projection from the inactive retina was substantially reduced. Thus, interocular competition driven by endogenous retinal activity determines the pattern of eye-specific connections from retina to LGN, demonstrating that spontaneous activity can produce highly stereotyped patterns of connections before the onset of visual experience.

Thalamic relay of spontaneous retinal activity prior to vision.

Before vision, retinal ganglion cells produce spontaneous waves of action potentials. A crucial question is whether this spontaneous activity is transmitted to lateral geniculate nucleus (LGN) neurons. Using a novel in vitro preparation, we report that LGN neurons receive periodic barrages of postsynaptic currents from the retina that drive them to fire bursts of action potentials. Groups of LGN neurons are highly correlated in their firing. Experiments in wild-type and NMDAR1 knockout mice show that NMDA receptor activation is not necessary for firing. The transmission of the highly correlated retinal activity to the LGN supports the hypothesis that retinal waves drive retinogeniculate synaptic remodeling. Because LGN neurons are driven to fire action potentials, this spontaneous activity could also act more centrally to influence synaptic modification within the developing visual cortex.

Mechanisms in experimental venous valve failure and their modification by Daflon 500 mg.

OBJECTIVES: To characterize the acute response of the vein wall to venous hypertension and associated altered fluid shear stress and to test the effect of micronized purified flavonoid fraction (MPFF, Daflon 500), on this response. MATERIAL AND METHODS: A femoral arteriovenous fistula was created in Wistar rats (n=48). A cohort of 24 rats received oral treatment with MPFF (100 mg/kg/day body weight), 24 rats underwent the arteriovenous fistula procedure and received no treatment. At days 1, 7 and 21 the animals (n=8 at each time point) were killed. Experimental parameters measured included limb circumference, blood flow at the sapheno-femoral junction, leukocyte infiltration and gelatinase activity (matrix metalloproteinase, MMP). RESULTS: The acute rise in venous hypertension was accompanied by limb edema and venous reflux together with an eventual loss of valve leaflets in the saphenous vein. There was an increase in granulocyte and macrophage infiltration into the venous wall and the surrounding tissue, and a lesser increase in T- and B-lymphocyte infiltration. These changes were accompanied by a local increase in the proteolytic enzymes, MMP-2 and MMP-9. Administration of MPFF reduced the edema and lessened the venous reflux produced by the acute arteriovenous fistula. Decreased levels of granulocyte and macrophage infiltration into the valves were also observed compared with untreated animals. CONCLUSIONS: Venous hypertension caused by an arteriovenous fistula resulted in the development of venous reflux and an inflammatory reaction in venous valves culminating in their destruction. MPFF was able to delay the development of reflux and suppress damage to the valve structures in this rat model of venous hypertension.

Differential Proteomics for Distinguishing Ischemic Stroke from Controls: a Pilot Study of the SpecTRA Project.

A diagnostic blood test for stroke is desirable but will likely require multiple proteins rather than a single "troponin." Validating large protein panels requires large patient numbers. Mass spectrometry (MS) is a cost-effective tool for this task. We compared differences in the abundance of 147 protein markers to distinguish 20 acute cerebrovascular syndrome (ACVS) patients who presented to the Emergency Department of one urban hospital within < 24 h from onset) and from 20 control patients who were enrolled via an outpatient neurology clinic. We targeted proteins from the stroke literature plus cardiovascular markers previously studied in our lab. One hundred forty-one proteins were quantified using MS, 8 were quantified using antibody protein enrichment with MS, and 32 were measured using ELISA, with some proteins measured by multiple techniques. Thirty proteins (4 by ELISA and 26 by the MS techniques) were differentially abundant between mimic and stroke after adjusting for age in robust regression analyses (FDR < 0.20). A logistic regression model using the first two principal components of the proteins significantly improved discrimination between strokes and controls compared to a model based on age alone (p < 0.001, cross-validated AUC 0.93 vs. 0.78). Significant proteins included markers of inflammation (47%), coagulation (40%), atrial fibrillation (7%), neurovascular unit injury (3%), and other (3%). These results suggest the potential value of plasma proteins as biomarkers for ACVS diagnosis and the role of plasma-based MS in this area.

Impact of prenatal diagnosis of fetus-in-fetu.

Fetus in fetu (FIF) is an extremely rare condition (1/500,000 live births) in which a fetiform structure is incorporated into the body of its twin. FIF can be a diagnostic dilemma due to its similarity to a teratoma, but identification of FIF is important for subsequent medical and surgical management. We compare two cases of fetal masses diagnosed on prenatal imaging that were later identified as FIF through further radiological, surgical, and pathologic evaluation. We use these cases to illustrate key pre- and postnatal features of FIF and highlight the benefits of prenatal detection and follow-up for postnatal management.

Perspectives of recent trainees on career choices in neonatology.

A major goal for neonatology training programs is to produce neonatologists who will pursue careers that combine clinical and research responsibilities. However, there appears to be a continuing decline in the number of trainees who choose academic, as opposed to private sector, jobs. The reason for this decline is perhaps best addressed by the people making career choices now, the recent trainees. Although many factors influence any individual's career choice, information from recent fellows indicates that several major factors play a strong role: finances; time demands; adequacy of research training; and academic institutions' attitudes toward recent trainees. Whereas the first two factors have been addressed by prior studies, the latter two factors have been less explored. The responses of a few recent trainees to an informal survey will be used to guide a discussion that focuses on the factors of research training and academic status. Ways to improve the success of training programs in producing academic neonatologists will be suggested, including the proposal of a research training curriculum, changes in the structure of post-fellowship academic status and increased encouragement of collaborative research efforts. A future survey of a broad group of recent trainees about their career choices and about proposals for training changes, such as those considered here, is needed to evaluate programs aimed at increasing the number of neonatologists engaged in research. Journal of Perinatology (2006) 26, S53-S56. doi:10.1038/sj.jp.7211527.

Dose-dependent size increases of aortic lesions following chronic exposure to 7,12-dimethylbenz(a)anthracene.

The prevalence, size, and patterns of distribution of arterial lesions (plaques) were investigated in cockerels exposed chronically to 7,12-dimethylbenz(a)anthracene (DMBA). Animals, from 5 to 20 weeks of age, received weekly i.m. injections of 5, 10, or 20 mg of DMBA per kg, dissolved in dimethyl sulfoxide. Control animals received weekly injections of dimethyl sulfoxide. All animals were sacrificed at 21 weeks of age. The entire aorta from each animal was cut transversely into 5-mm segments starting at the iliac trifurcation. The cross-sectional area of plaques was determined by light microscopic analysis of sections taken from the face of each segment. Plaque frequency was similar in DMBA-treated and control groups. However, mean plaque cross-sectional area was 7- to 11-fold higher for the treatment groups than for the controls. The distribution of plaque areas in both treated animals and controls was consistent with a log normal distribution. Median cross-sectional area and plaque volume index each increased in a linear fashion with DMBA dose. Small plaques were present in all groups. Large plaques were present only in DMBA-treated animals. Labeling indices of plaques, although low, were 2.3- to 26-fold higher than for underlying medial smooth muscle cells. The data indicate that the primary response to chronic DMBA exposure is a dose-dependent size increase of spontaneous aortic lesions and not the induction of new lesions.

Zidovudine and dideoxynucleosides deplete wild-type mitochondrial DNA levels and increase deleted mitochondrial DNA levels in cultured Kearns-Sayre syndrome fibroblasts.

Kearns-Sayre syndrome is the most commonly diagnosed mitochondrial cytopathy and produces severe neuromuscular symptoms. The most frequent cause is a mitochondrial DNA deletion that removes a 4977-base pair segment of DNA that includes several genes encoding for respiratory chain subunits. Treatment of AIDS patients with nucleoside analogs has been reported to cause mtDNA depletion and myopathies. Here, we report that azidothymidine, dideoxyguanosine, and dideoxycytidine cause a depletion of wild-type mtDNA while increasing the levels of deleted mitochondria DNA in Kearns-Sayre syndrome fibroblasts. The result of these effects is a large increase in the relative amounts of delta mtDNA in comparison to wild type mtDNA. We found that Kearns-Sayre syndrome fibroblasts are a mixed population of cells with deleted mtDNA comprising from 0 to over 20% of the total mtDNA in individual cells. Treatment of cloned cell lines with dideoxycytidine did not result in increased levels of delta mtDNA. The results suggest that nucleoside analogs may act to increase the average delta mtDNA levels in a mixed population of cells by preferentially inhibiting the proliferation of cells with little or no delta mtDNA. This raises the possibility that modulation of deleted mtDNA levels may occur by similar mechanisms in vivo, in response to the influence of exogenous agents.

Low serum thiol levels predict shorter times-to-death among HIV-infected injecting drug users.

OBJECTIVES: To investigate whether serum thiol levels are altered by HIV disease, and whether low serum thiols predict time to death among HIV-infected injecting drug users (IDU). DESIGN: A cross-sectional study of serum thiol levels among 13 HIV-seronegative IDU, 116 HIV-seropositive IDU, and 17 HIV-seropositive IDU with a history of AIDS, and a cohort study of the 133 HIV-infected IDU who took part in the cross-sectional study. METHODS: Subjects were recruited from a methadone-maintenance treatment program during 1990-1991. Total serum thiols were determined spectrophotometrically at enrolment; low serum thiols were defined as those with an absorbance at 412 nm < or = 0.46. Deaths through 31 December 1993 were determined from the National Death Index (NDI). Twenty-six HIV-seropositive subjects died during follow up; death certificates, which were obtained for 23 subjects, indicated AIDS or HIV infection for 20. Product-limit estimation was used to calculate survival. Multivariate analyses employed Cox proportional-hazards regression. RESULTS: Analysis of cross-sectional data showed that serum thiols did not differ significantly among HIV-free subjects, HIV-infected subjects, and HIV-infected subjects with a history of AIDS. Cohort analysis, adjusted for age, revealed that persons with those with high serum thiols (relative hazard = 2.83; 95% confidence interval (CI), 1.15, 6.97); a significant interaction between low serum thiols and a history of AIDS was associated with a relative hazard of 5.65 (95% CI, 1.22-2.61). CONCLUSIONS: Among HIV-infected persons, low serum thiols, especially in concert with a history of AIDS, predict mortality risk. These findings support the hypothesis that oxidative stress is critical to the pathogenesis of HIV infection.

Adenovirus-mediated factor VIII gene expression results in attenuated anti-factor VIII-specific immunity in hemophilia A mice compared with factor VIII protein infusion.

Hemophilia A patients are typically treated by factor VIII (FVIII) protein replacement, an expensive therapy that induces FVIII-specific inhibitors in approximately 30% of patients with severe hemophilia. FVIII gene therapy has the potential to improve the current treatment protocols. In this report, we used a hemophilia A mouse model to compare the humoral and cellular immune responses between an E1/E2a/E3-deficient adenovirus expressing human FVIII directed by a liver-specific albumin promoter and purified recombinant FVIII protein infusion. Adenovirus-mediated FVIII expression did not elicit detectable CD4+ or CD8+ T cell responses and induced a weak antibody immune response to FVIII. In contrast, FVIII protein administration resulted in a potent anti-FVIII antibody response and moderate CD4+ T cell response. Furthermore, hemophiliac mice preimmunized with FVIII protein infusion to induce anti-FVIII immunity, and subsequently treated by adenovirus-mediated FVIII gene therapy, expressed therapeutic levels of FVIII despite the presence of low levels of anti-FVIII antibodies. No FVIII was detected in the plasma of mice with intermediate or high antibody levels, although anti-FVIII antibody levels in some vector-treated animals declined. The data support the hypothesis that liver-specific gene therapy-mediated expression of FVIII may be less immunogenic than traditional protein replacement therapy.

In vivo evaluation of an adenoviral vector encoding canine factor VIII: high-level, sustained expression in hemophiliac mice.

Hemophilia A is the most common severe hereditary coagulation disorder and is caused by a deficiency in blood clotting factor VIII (FVIII). Canine hemophilia A represents an excellent large animal model that closely mimicks the human disease. In previous studies, treatment of hemophiliac dogs with an adenoviral vector encoding human FVIII resulted in complete correction of the coagulation defect and high-level FVIII expression [Connelly et al. (1996). Blood 88, 3846]. However, FVIII expression was short term, limited by a strong antibody response directed against the human protein. Human FVIII is highly immunogenic in dogs, whereas the canine protein is significantly less immunogenic. Therefore, sustained phenotypic correction of canine hemophilia A may require the expression of the canine protein. In this work, we have isolated the canine FVIII cDNA and generated an adenoviral vector encoding canine FVIII. We demonstrate expression of canine FVIII in hemophiliac mice at levels 10-fold higher than those of the human protein expressed from an analogous vector. Canine FVIII expression was sustained above human therapeutic levels (50 mU/ml) for at least 1 year in hemophiliac mice.