Investigating the modulation of stimulus types on language switching costs: Do semantic and repetition priming effect matter?

Introduction: In the present study, I investigated the influence of stimulus types on bilingual control in the language switching process. The commonly employed stimuli in language switching studies - Arabic digits and objects - were compared to further investigate the way in which inhibitory control could be modulated by semantic and repetition priming effects. The digit stimuli have two unique characteristics in the language switching paradigm, for example, they are present repeatedly and are semantically related to each other, compared with pictural stimuli. Thus, these unique characteristics might influence the operation of inhibitory control in bilingual language production, modulating the size and asymmetry of switching costs. Methods: Two picture control sets were set up to match those characteristics: (1) a semantic control set, in which picture stimuli belong to the same category group, such as, animals, occupations or transportation and specific semantic categories were presented in a blocked condition; and (2) a repeated control set, in which nine different picture stimuli were repeatedly presented like the Arabic digits from 1 to 9. Results: When comparing the digit condition and the standard picture condition, analyses of naming latencies and accuracy rates revealed that switching costs were reliably smaller for digit naming than for picture naming and the L1 elicited more switching costs for picture naming than for digit naming. On the other hand, when comparing the digit condition and the two picture control sets, it was found that the magnitude of switching costs became identical and the asymmetry in switching costs became much smaller between the two languages.

Investigating the modulation of active preparation and passive dissipation on inhibitory control processes in the language switching paradigm.

Introduction: Previous language-switching studies have received scholastic attention and the observed switching cost patterns have provided empirical evidence for bilingual language control. However, results are inconsistent as the size of and (a)symmetry in switching costs differ across studies. In addition, there are various methodological differences that go beyond stimulus differences, such as the language proficiency of the participants (the participant-level factor) and the preparation time (a task-related level factor), which might be responsible for these inconsistent results. Methods: With a focus on task-related factors, the present study was designed to examine whether and how preparation time modulates the size and (a)symmetry in switching costs by using the language-switching paradigm with cue-to-stimulus and response-to-cue intervals manipulated. Results: Replicating previous literature on language switching and task switching, a clear preparation effect was observed in all trials (stay and switch trials) for both L1 and L2. The switching costs were modulated by the cue-to-stimulus intervals, and specifically, switching costs decreased when the preparation time increased. Another intriguing finding was that even when participants were offered enough time to fully prepare for selecting the target language at the cue window, the switching costs were not completely eliminated. In terms of the passive preparation at the response-to-cue interval, switching costs could be modulated by the response-to-cue interval - the time for passive dissipation of inhibitory control applied in previous trials. The size of switching costs was clearly modulated by manipulating response-to-cue intervals and switching costs decreased as the waiting time after a naming response increased. Discussion: This study provides empirical evidence for the modulation of preparation effects on switching costs and inhibitory control mechanisms in bilingual language production.

The forkhead transcription factor UNC-130/FOXD integrates both BMP and Notch signaling to regulate dorsoventral patterning of the C. elegans postembryonic mesoderm.

The proper development of a multicellular organism requires precise spatial and temporal coordination of cell intrinsic and cell extrinsic regulatory mechanisms. Both Notch signaling and bone morphogenetic protein (BMP) signaling function to regulate the proper development of the C. elegans postembryonic mesoderm. We have identified the C. elegans FOXD transcription factor UNC-130 as a major target functioning downstream of both BMP signaling and Notch signaling to regulate dorsoventral patterning of the postembryonic mesoderm. We showed that unc-130 expression in the postembryonic M lineage is asymmetric: its absence of expression in the dorsal side of the M lineage requires the antagonism of BMP signaling by the zinc finger transcription factor SMA-9, while its expression in the ventral side of the M lineage is activated by LIN-12/Notch signaling. We further showed that the regulation of UNC-130 expression by BMP signaling and Notch signaling is specific to the M lineage, as the ventral expression of UNC-130 in the embryonically-derived bodywall muscles was not affected in either BMP pathway or Notch pathway mutants. Finally, we showed that the function of UNC-130 in the M lineage is independent of UNC-129, a gene previously shown to function downstream of and be repressed by UNC-130 for axon guidance. Our studies uncovered a new function of UNC-130/FOXD in the C. elegans postembryonic mesoderm, and identify UNC-130 as a critical factor that integrates two independent spatial cues for the proper patterning and fate specification of the C. elegans postembryonic mesoderm.

The C. elegans Spalt-like protein SEM-4 functions through the SoxC transcription factor SEM-2 to promote a proliferative blast cell fate in the postembryonic mesoderm.

Proper development of a multicellular organism relies on well-coordinated regulation of cell fate specification, cell proliferation and cell differentiation. The C. elegans postembryonic mesoderm provides a useful system for uncovering factors involved in these processes and for further dissecting their regulatory relationships. The single Spalt-like zinc finger containing protein SEM-4/SALL is known to be involved in specifying the proliferative sex myoblast (SM) fate. We have found that SEM-4/SALL is sufficient to promote the SM fate and that it does so in a cell autonomous manner. We further showed that SEM-4/SALL acts through the SoxC transcription factor SEM-2 to promote the SM fate. SEM-2 is known to promote the SM fate by inhibiting the expression of two BWM-specifying transcription factors. In light of recent findings in mammals showing that Sall4, one of the mammalian homologs of SEM-4, contributes to pluripotency regulation by inhibiting differentiation, our work suggests that the function of SEM-4/SALL proteins in regulating pluripotency versus differentiation appears to be evolutionarily conserved.

Membrane trafficking. Nucleoside diphosphate kinases fuel dynamin superfamily proteins with GTP for membrane remodeling.

Dynamin superfamily molecular motors use guanosine triphosphate (GTP) as a source of energy for membrane-remodeling events. We found that knockdown of nucleoside diphosphate kinases (NDPKs) NM23-H1/H2, which produce GTP through adenosine triphosphate (ATP)-driven conversion of guanosine diphosphate (GDP), inhibited dynamin-mediated endocytosis. NM23-H1/H2 localized at clathrin-coated pits and interacted with the proline-rich domain of dynamin. In vitro, NM23-H1/H2 were recruited to dynamin-induced tubules, stimulated GTP-loading on dynamin, and triggered fission in the presence of ATP and GDP. NM23-H4, a mitochondria-specific NDPK, colocalized with mitochondrial dynamin-like OPA1 involved in mitochondria inner membrane fusion and increased GTP-loading on OPA1. Like OPA1 loss of function, silencing of NM23-H4 but not NM23-H1/H2 resulted in mitochondrial fragmentation, reflecting fusion defects. Thus, NDPKs interact with and provide GTP to dynamins, allowing these motor proteins to work with high thermodynamic efficiency.

Mutations in Fis1 disrupt orderly disposal of defective mitochondria.

Mitochondrial fission is mediated by the dynamin-related protein Drp1 in metazoans. Drp1 is recruited from the cytosol to mitochondria by the mitochondrial outer membrane protein Mff. A second mitochondrial outer membrane protein, named Fis1, was previously proposed as recruitment factor, but Fis1(-/-) cells have mild or no mitochondrial fission defects. Here we show that Fis1 is nevertheless part of the mitochondrial fission complex in metazoan cells. During the fission cycle, Drp1 first binds to Mff on the surface of mitochondria, followed by entry into a complex that includes Fis1 and endoplasmic reticulum (ER) proteins at the ER-mitochondrial interface. Mutations in Fis1 do not normally affect fission, but they can disrupt downstream degradation events when specific mitochondrial toxins are used to induce fission. The disruptions caused by mutations in Fis1 lead to an accumulation of large LC3 aggregates. We conclude that Fis1 can act in sequence with Mff at the ER-mitochondrial interface to couple stress-induced mitochondrial fission with downstream degradation processes.

Construction and application of the vectors to identify genes encoding exported proteins of Escherichia coli.

In order to clone genes having signal sequences of Escherichia coli, four vectors with or without Lac or Ara promoter were constructed using a leaderless ß-lactamase as reporter. Fragments of tetracycline resistance gene (Tet) with or without promoter were used to confirm the vectors' ability to clone and report signal sequences. The minimum inhibitory concentration of ampicillin of the transformants was measured to detect the expression and secretion efficiency of the vectors. The results showed that the ß-lactamase could be co-expressed and secreted with Tet protein. The Lac or Ara promoter in the vectors could be regulated by different inducers, and the Ara promoter showed higher regulative efficiency than the Lac. The best induction dose of L-arabinose for the Ara promoter is 1.25 %. All the four vectors were stably maintained in host after being inoculated for 20 passages in antibiotics-free media. Genomic library of an avian pathogenic strain, E. coli O2, was constructed using the pMB-Ara-T vector we developed. 318 clones were obtained from the genomic library of E. coli strain O2, and the inserts in these clones represented 276 genes based on sequence analysis. Among the 276 cloned fragments, only 128 had complete promoter sequence. For the 128 fragments with promoter, only 27 could be expressed under LB culture condition without inducer, the other 101 were only expressed under induction. The results showed our constructed vectors could efficiently capture all kinds of exported protein genes in vitro, including the ones without promoter or with inactive promoter.

Mechanisms of mitochondrial fission and fusion.

Mitochondria continually change shape through the combined actions of fission, fusion, and movement along cytoskeletal tracks. The lengths of mitochondria and the degree to which they form closed networks are determined by the balance between fission and fusion rates. These rates are influenced by metabolic and pathogenic conditions inside mitochondria and by their cellular environment. Fission and fusion are important for growth, for mitochondrial redistribution, and for maintenance of a healthy mitochondrial network. In addition, mitochondrial fission and fusion play prominent roles in disease-related processes such as apoptosis and mitophagy. Three members of the Dynamin family are key components of the fission and fusion machineries. Their functions are controlled by different sets of adaptor proteins on the surface of mitochondria and by a range of regulatory processes. Here, we review what is known about these proteins and the processes that regulate their actions.

Caenorhabditis elegans protein arginine methyltransferase PRMT-5 negatively regulates DNA damage-induced apoptosis.

Arginine methylation of histone and non-histone proteins is involved in transcription regulation and many other cellular processes. Nevertheless, whether such protein modification plays a regulatory role during apoptosis remains largely unknown. Here we report that the Caenorhabditis elegans homolog of mammalian type II arginine methyltransferase PRMT5 negatively regulates DNA damage-induced apoptosis. We show that inactivation of C. elegans prmt-5 leads to excessive apoptosis in germline following ionizing irradiation, which is due to a CEP-1/p53-dependent up-regulation of the cell death initiator EGL-1. Moreover, we provide evidence that CBP-1, the worm ortholog of human p300/CBP, functions as a cofactor of CEP-1. PRMT-5 forms a complex with both CEP-1 and CBP-1 and can methylate the latter. Importantly, down-regulation of cbp-1 significantly suppresses DNA damage-induced egl-1 expression and apoptosis in prmt-5 mutant worms. These findings suggest that PRMT-5 likely represses CEP-1 transcriptional activity through CBP-1, which represents a novel regulatory mechanism of p53-dependent apoptosis.

Adenine nucleotide translocator cooperates with core cell death machinery to promote apoptosis in Caenorhabditis elegans.

In Caenorhabditis elegans, the central cell-killing process is essentially controlled by the interplay of four apoptotic factors: EGL-1/BH3-only protein, CED-9/Bcl2, CED-4/Apaf1, and CED-3/caspase. In cells destined to die, EGL-1 binds to CED-9 and results in the release of CED-4 from the mitochondrion-tethered CED-9-CED-4 complex to the perinucleus, which facilitates processing of the CED-3 caspase to cause apoptosis. However, whether additional factors exist to regulate the cell-killing process remains largely unknown. We have identified here WAN-1, the C. elegans ortholog of mammalian adenine nucleotide translocator, as an important cell death regulator. Genetic inactivation of wan-1 significantly suppressed both somatic and germ line cell deaths in C. elegans. Consistently, chemical inhibition of WAN-1 activity also caused strong reduction of germ line apoptosis. WAN-1 localizes to mitochondria and can form complex with both CED-4 and CED-9. Importantly, the cell death initiator EGL-1 can disrupt the interaction between CED-9 and WAN-1. In addition, overexpression of WAN-1 induced ectopic cell killing dependently on the core cell death pathway. These findings suggest that WAN-1 is involved in the central cell-killing process and cooperates with the core cell death machinery to promote programmed cell death in C. elegans.

[Cloning and analysis of the complete genome of a Goose circovirus from Yongkang Zhejiang].

To investigate the mechanism of avian influenza outbreak wildly in water fowls, the co-pathogens, especially that caused immuno-depression were studied. A pair of degenerated primers, which amplified a fragment of 552bp in length, was designed and synthesized based on the published goose and other Circovirus sequences. The specific PCR product was amplified from the goose sample of Yongkang avian influenza case of Zhejiang Province. The fragment was then sequenced and the result showed the existence of the GoCV. The opposite part of the genome was further amplified using inverse primers designed based on the 552bp sequence obtained and the 1821bp full length genomic sequence of GoCV-yk01 was compiled using Seqman program of DNAStar. Sequence analysis showed that the GoCV-yk01 possessed common features of circovirus included potential replication associated stem-loop structure and the Rep protein motifs. Homology analysis showed that the sequence of GoCV-yk01 had 91% approximately 93% similarity to that of Taiwan and Germany strains. Phylogenetic analysis with ClustalW, however, showed that the GoCV-yk01 was on a different branch away from Taiwan and Germany strains. Circovirus usually causes immuno-depression and results in secondary infection, as it infects rapid growing cells as lymphocyte. It is speculated that the infection of GoCV may be a part of the reason of the avian influenza outbreak of the Yongkang case. The GoCV-yk01 is the first GoCV strain reported in mainland of China.