Second language processing shows increased native-like neural responses after months of no exposure

Although learning a second language (L2) as an adult is notoriously difficult, research has shown that adults can indeed attain native language-like brain processing and high proficiency levels. However, it is important to then retain what has been attained, even in the absence of continued exposure to the L2--particularly since periods of minimal or no L2 exposure are common. This event-related potential (ERP) study of an artificial language tested performance and neural processing following a substantial period of no exposure. Adults learned to speak and comprehend the artificial language to high proficiency with either explicit, classroom-like, or implicit, immersion-like training, and then underwent several months of no exposure to the language. Surprisingly, proficiency did not decrease during this delay. Instead, it remained unchanged, and there was an increase in native-like neural processing of syntax, as evidenced by several ERP changes--including earlier, more reliable, and more left-lateralized anterior negativities, and more robust P600s, in response to word-order violations. Moreover, both the explicitly and implicitly trained groups showed increased native-like ERP patterns over the delay, indicating that such changes can hold independently of L2 training type. The results demonstrate that substantial periods with no L2 exposure are not necessarily detrimental. Rather, benefits may ensue from such periods of time even when there is no L2 exposure. Interestingly, both before and after the delay the implicitly trained group showed more native-like processing than the explicitly trained group, indicating that type of training also affects the attainment of native-like processing in the brain. Overall, the findings may be largely explained by a combination of forgetting and consolidation in declarative and procedural memory, on which L2 grammar learning appears to depend. The study has a range of implications, and suggests a research program with potentially important consequences for second language acquisition and related fields.     

Single particle characterization of iron-induced pore-forming alpha-synuclein oligomers

Aggregation of alpha-synuclein is a key event in several neurodegenerative diseases, including Parkinson disease. Recent findings suggest that oligomers represent the principal toxic aggregate species. Using confocal single-molecule fluorescence techniques, such as scanning for intensely fluorescent targets (SIFT) and atomic force microscopy, we monitored alpha-synuclein oligomer formation at the single particle level. Organic solvents were used to trigger aggregation, which resulted in small oligomers ("intermediate I"). Under these conditions, Fe(3+) at low micromolar concentrations dramatically increased aggregation and induced formation of larger oligomers ("intermediate II"). Both oligomer species were on-pathway to amyloid fibrils and could seed amyloid formation. Notably, only Fe(3+)-induced oligomers were SDS-resistant and could form ion-permeable pores in a planar lipid bilayer, which were inhibited by the oligomer-specific A11 antibody. Moreover, baicalein and N'-benzylidene-benzohydrazide derivatives inhibited oligomer formation. Baicalein also inhibited alpha-synuclein-dependent toxicity in neuronal cells. Our results may provide a potential disease mechanism regarding the role of ferric iron and of toxic oligomer species in Parkinson diseases. Moreover, scanning for intensely fluorescent targets allows high throughput screening for aggregation inhibitors and may provide new approaches for drug development and therapy.     

Sorting food from stones: the vagal taste system in Goldfish, Carassius auratus

The sense of taste, although a relatively undistinguished sensory modality in most mammals, is a highly developed sense in many fishes, e.g., catfish, gadids, and carps including goldfish. In these species, the amount of neural tissue devoted to this modality may approach 20% of the entire brain mass, reflecting an enormous number of taste buds scattered across the external surface of the animal as well as within the oral cavity. The primary sensory nuclei for taste form a longitudinal column of nuclei along the dorsomedial surface of the medulla. Within this column of gustatory nuclei, the sensory system is represented as a fine-grain somatotopic map, with external body parts being represented rostrally within the column, and oropharyngeal surfaces being represented caudally. Goldfish have a specialization of the oral cavity, the palatal organ, which enables them to sort food particles from particulate substrate material such as gravel. The palatal organ taste information reaches the large, vagal lobe with a complex laminar and columnar organization. This lobe also supports a radially-organized reflex system which activates the musculature of the palatal organ to effect the sorting operation. The stereotyped, laminated structure of this system in goldfish has facilitated studies of the circuitry and neurotransmitter systems underlying the goldfish’s ability to sort food from stones.     

Tracking global invasion pathways of the spongy moth (Lepidoptera: Erebidae) to the United States using stable isotopes as endogenous biomarkers

The spread of invasive insect species causes enormous ecological damage and economic losses worldwide. A reliable method that tracks back an invaded insect''s origin would be of great use to entomologists, phytopathologists, and pest managers. The spongy moth (Lymantria dispar, Linnaeus 1758) is a persistent invasive pest in the Northeastern United States and periodically causes major defoliations in temperate forests. We analyzed field‐captured (Europe, Asia, United States) and laboratory‐reared L. dispar specimens for their natal isotopic hydrogen and nitrogen signatures imprinted in their biological tissues (δ²H and δ¹⁵N) and compared these values to the long‐term mean δ²H of regional precipitation (Global Network of Isotopes in Precipitation) and δ¹⁵N of regional plants at the capture site. We established the percentage of hydrogen–deuterium exchange for L. dispar tissue (P_ex = 8.2%) using the comparative equilibration method and two‐source mixing models, which allowed the extraction of the moth''s natal δ²H value. We confirmed that the natal δ²H and δ¹⁵N values of our specimens are related to the environmental signatures at their geographic origins. With our regression models, we were able to isolate potentially invasive individuals and give estimations of their geographic origin. To enable the application of these methods on eggs, we established an egg‐to‐adult fraction factor for L. dispar (Δegg‐adult = 16.3 ± 4.3‰). Our models suggested that around 25% of the field‐captured spongy moths worldwide were not native in the investigated capture sites. East Asia was the most frequently identified location of probable origin. Furthermore, our data suggested that eggs found on cargo ships in the United States harbors in Alaska, California, and Louisiana most probably originated from Asian L. dispar in East Russia. These findings show that stable isotope biomarkers give a unique insight into invasive insect species pathways, and thus, can be an effective tool to monitor the spread of insect pest epidemics.     

Low Levels of Nucleotide Diversity in Crocodylus moreletii and Evidence of Hybridization with C. acutus

Examinations of both population genetic structure and the processes that lead to such structure in crocodilians have been initiated in several species in response to a call by the IUCN Crocodile Specialist Group. A recent study used microsatellite markers to characterize Morelet's crocodile (Crocodylus moreletii) populations in north-central Belize and presented evidence for isolation by distance. To further investigate this hypothesis, we sequenced a portion of the mitochondrial control region for representative animals after including samples from additional locales in Belize, Guatemala and Mexico. While there is limited evidence of subdivision involving other locales, we found that most of the differentiation among populations of C. moreletiican be attributed to animals collected from a single locale in Belize, Banana Bank Lagoon. Furthermore, mitochondrial DNA sequence analysis showed that animals from this and certain other locales display a haplotype characteristic of the American crocodile, C. acutus, rather than C. moreletii. We interpret this as evidence of hybridization between the two species and comment on how these new data have influenced our interpretation of previous findings. We also find very low levels of nucleotide diversity in C. moreletiihaplotypes and provide evidence for a low rate of substitution in the crocodilian mitochondrial control region. Finally, the conservation implications of these findings are discussed.     

Temporal variation in constitutive and inducible heat shock proteins in the Zebra Finch Taeniopygia guttata

Cellular stressors initiate the heat shock response mediated by heat shock proteins (HSPs). There are two main types of HSPs, constitutive (always expressed) and inducible (upon stress), but as many in vivo studies fail to distinguish between them and because temporal expression patterns often differ among various types of HSPs, it is unclear when to measure HSPs. In this study, 26 (13 per treatment) adult female Zebra Finches Taeniopygia guttata were heat‐stressed (39 °C) or placed in a control brooder (room temperature) for 3 h and were bled 1 week prior to and at 1, 2, 4, 6 and 20 h post‐treatment. Treatment had no effect on levels of either constitutive HSP70 or inducible HSP90, but both HSPs decreased with time relative to baseline, suggesting a possible effect of handling stress and/or circadian variation.     

Use of single nucleotide polymorphisms identifies backcrossing and species misidentifications among three San Francisco estuary osmerids

Two threatened osmerid species native to the San Francisco Estuary (SFE)—Delta Smelt (Hypomesus transpacificus) and Longfin Smelt (Spirinchus thaleichthys)—are subject to broad human influence, including significant habitat alteration and the presence of the introduced osmerid, Wakasagi (Hypomesus nipponensis). The identification of these closely related species and their hybrids is difficult in field collected specimens which are subject to damage through handling and may be difficult to identify morphologically, especially when young. In addition, it is known that these three species hybridize, but the extent and effect of hybridization is difficult to quantify and monitor. We developed assays for 24 species-specific single nucleotide polymorphisms (SNPs) that identify whether a sample is a pure species (Delta Smelt, Longfin Smelt, or Wakasagi), a first generation (F₁) hybrid, or a backcross. We used this SNP panel to genetically identify wild osmerids collected in Yolo Bypass from 2010 to 2016 and detected nine Delta Smelt × Wakasagi F₁ hybrids and two Wakasagi × (Delta Smelt × Wakasagi) backcross hybrids; all assayed hybrids had Wakasagi as the maternal parent. The backcrossing into Wakasagi suggests that hybridization may only occur in one direction and thus preclude introgression to Delta Smelt. We also found substantial morphological field misidentifications (32.7%) in the Yolo Bypass samples resulting in more Wakasagi and fewer Delta Smelt than previously recorded when based on morphology. The SNP panel described in this study constitutes a valuable resource for monitoring hybridization in the SFE and assigning species identifications with accuracy and efficiency.     

Influence of the cystic fibrosis transmembrane conductance regulator on expression of lipid metabolism-related genes in dendritic cells

Background

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Infections of the respiratory tract are a hallmark in CF. The host immune responses in CF are not adequate to eradicate pathogens, such as P. aeruginosa. Dendritic cells (DC) are crucial in initiation and regulation of immune responses. Changes in DC function could contribute to abnormal immune responses on multiple levels. The role of DC in CF lung disease remains unknown.

Methods

This study investigated the expression of CFTR gene in bone marrow-derived DC. We compared the differentiation and maturation profile of DC from CF and wild type (WT) mice. We analyzed the gene expression levels in DC from naive CF and WT mice or following P. aeruginosa infection.

Results

CFTR is expressed in DC with lower level compared to lung tissue. DC from CF mice showed a delayed in the early phase of differentiation. Gene expression analysis in DC generated from naive CF and WT mice revealed decreased expression of Caveolin-1 (Cav1), a membrane lipid raft protein, in the CF DC compared to WT DC. Consistently, protein and activity levels of the sterol regulatory element binding protein (SREBP), a negative regulator of Cav1 expression, were increased in CF DC. Following exposure to P. aeruginosa, expression of 3β-hydroxysterol-Δ7 reductase (Dhcr7) and stearoyl-CoA desaturase 2 (Scd2), two enzymes involved in the lipid metabolism that are also regulated by SREBP, was less decreased in the CF DC compared to WT DC.

Conclusion

These results suggest that CFTR dysfunction in DC affects factors involved in membrane structure and lipid-metabolism, which may contribute to the abnormal inflammatory and immune response characteristic of CF.