People living in multicultural environments often encounter situations which require them to acquire different cultural schemas and to switch between these cultural schemas depending on their immediate sociocultural context. Prior behavioral studies show that priming cultural schemas reliably impacts mental processes and behavior underlying self-concept. However, less well understood is whether or not cultural priming affects neurobiological mechanisms underlying the self. Here we examined whether priming cultural values of individualism and collectivism in bicultural individuals affects neural activity in cortical midline structures underlying self-relevant processes using functional magnetic resonance imaging. Biculturals primed with individualistic values showed increased activation within medial prefrontal cortex (MPFC) and posterior cingulate cortex (PCC) during general relative to contextual self-judgments, whereas biculturals primed with collectivistic values showed increased response within MPFC and PCC during contextual relative to general self-judgments. Moreover, degree of cultural priming was positively correlated with degree of MPFC and PCC activity during culturally congruent self-judgments. These findings illustrate the dynamic influence of culture on neural representations underlying the self and, more broadly, suggest a neurobiological basis by which people acculturate to novel environments.

Individualism and collectivism refer to cultural values that influence how people construe themselves and their relation to the world. Individualists perceive themselves as stable entities, autonomous from other people and their environment, while collectivists view themselves as dynamic entities, continually defined by their social context and relationships. Despite rich understanding of how individualism and collectivism influence social cognition at a behavioral level, little is known about how these cultural values modulate neural representations underlying social cognition. Using cross-cultural functional magnetic resonance imaging (fMRI), we examined whether the cultural values of individualism and collectivism modulate neural activity within medial prefrontal cortex (MPFC) during processing of general and contextual self judgments. Here, we show that neural activity within the anterior rostral portion of the MPFC during processing of general and contextual self judgments positively predicts how individualistic or collectivistic a person is across cultures. These results reveal two kinds of neural representations of self (eg, a general self and a contextual self) within MPFC and demonstrate how cultural values of individualism and collectivism shape these neural representations.

Eye contact provides a communicative link between humans, prompting joint attention. As spontaneous brain activity might have an important role in the coordination of neuronal processing within the brain, their inter-subject synchronization might occur during eye contact. To test this, we conducted simultaneous functional MRI in pairs of adults. Eye contact was maintained at baseline while the subjects engaged in real-time gaze exchange in a joint attention task. Averted gaze activated the bilateral occipital pole extending to the right posterior superior temporal sulcus, the dorso-medial prefrontal cortex, and the bilateral inferior frontal gyrus. Following a partner's gaze toward an object activated the left intraparietal sulcus. After all the task-related effects were modeled out, inter-individual correlation analysis of residual time-courses was performed. Paired subjects showed more prominent correlations than non-paired subjects in the right inferior frontal gyrus, suggesting that this region is involved in sharing intention during eye contact that provides the context for joint attention.

Mainly based on various inhibitor studies previously performed, amidases came to be regarded as sulfhydryl enzymes. Not completely satisfied with this generally accepted interpretation, we performed a series of sitedirected mutagenesis studies on one particular amidase of Rhodococcus rhodochrous J1 that was involved in its nitrile metabolism. For these experiments, the recombinant amidase was produced as the inclusion body in Escherichia coli to greatly facilitate its recovery and subsequent purification. With regard to the presumptive active site residue Cys203, a Cys203 3 Ala mutant enzyme still retained 11.5% of the original specific activity. In sharp contrast, substitutions in certain other positions in the neighborhood of Cys203 had a far more dramatic effect on the amidase. Glutamic acid substitution of Asp191 reduced the specific activity of the mutant enzyme to 1.33% of the wild-type activity. Furthermore, Asp191 3 Asn substitution as well as Ser195 3 Ala substitution completely abolished the specific activity. It would thus appear that, among various conserved residues residing within the so-called signature sequence common to all amidases, the real active site residues are Asp191 and Ser195 rather than Cys203. Inasmuch as an amide bond (CO-NH 2 ) in the amide substrate is not too far structurally removed from a peptide bond (CO-NH-), the signature sequences of various amidases were compared with the active site sequences of various types of proteases. It was found that aspartic acid and serine residues corresponding to Asp191 and Ser195 of the Rhodococcus amidase are present within the active site sequences of aspartic proteinases, thus suggesting the evolutionary relationship between the two.

An enzyme "alkylaldoxime dehydratase (OxdRG)" was purified and characterized from Rhodococcus globerulus A-4, in which nitrile hydratase (NHase) and amidase coexisted with the enzyme. The enzyme contains heme b as a prosthetic group, requires reducing reagents for the reaction, and is most active at a neutral pH and at around 30°C, similar to the phenylacetaldoxime dehydratase from Bacillus sp. OxB-1 (OxdB). However, some differences were seen in subunit structure, substrate specificity, and effects of activators and inhibitors. The corresponding gene, oxd, encoding a 1059-base pair ORF consisting of 353 codons, was cloned, sequenced, and overexpressed in Escherichia coli. The predicted polypeptide showed 30.3% identity to OxdB. The gene is mapped just upstream of the gene cluster encoding the enzymes involved in the metabolism of aliphatic nitriles, i.e., NHase and amidase, and their regulatory and activator proteins. We report here the existence of an aldoxime dehydratase genetically linked with NHase and amidase, and responsible for the metabolism of alkylaldoxime in R. globerulus.Aldoximes derived from amino acids are considered to be intermediates in the biosynthesis of cyanogenic glucosides and glucosinolates in plants (1). However, information on aldoxime metabolism is quite limited and the genetics and enzymology have not been well characterized. One oximemetabolizing enzyme (cytochrome P450 CYP71E1) has been reported to catalyze the conversion of aldoxime to R-hydroxynitrile in the pathway for biosynthesis of cyanogenic glucoside dhurrin in Sorghum bicolor (2-4). Other cytochrome P450s, namely, CYP83 homologues (A1 and B1), have also been identified as oxime-metabolizing enzymes, which catalyze the conversion of indoleacetaldoxime to the corresponding aci-nitro compound, the first step in the biosynthesis of indole glucosinolates in Arabidopsis thaliana. However, the level of activity is quite low, and the mechanisms involved have not been studied. Indoleacetaldoxime is known to be a metabolic branch point between the production of indoleacetic acid and indole glucosinolates in A. thaliana (5-7), but the enzymes responsible for the metabolism have yet to be purified and characterized.Asano et al. have isolated various nitrile-degrading microorganisms, e.g., Rhodococcus rhodochrous (formerly Arthrobacter sp.) strains J-1 and I-9 (K22, AKU 629) (8) and Pseudomonas chlororaphis B23 (9). They first purified, characterized, and named nitrile hydratase (NHase, EC. 4.2.1.84) from R. rhodochrous J-1 (10-12). They also found that P. chlororaphis B23 accumulates large quantities of amides from nitriles and is suitable for the industrial production of acrylamide from acrylonitrile (9, 12). Moreover, nicotinamide and 5-cyanovaleramide are also industrially produced by NHase (13,14). Despite its important uses, the physiological function of NHase in nature remains unclear.We have studied the metabolism of aldoximes from a physiological as well as an applicative perspective, and have isolated Bacillus sp. O...