Studies of young infants are critical to understand perceptual, motor, and cognitive processing in humans. However, brain mechanisms involved are poorly understood, because the use of brainimaging methods such as functional magnetic resonance imaging in awake infants is difficult. In the present study we show functional brain imaging of awake infants viewing visual stimuli by means of multichannel near-infrared spectroscopy, a technique that permits a measurement of cerebral hemoglobin oxygenation in response to brain activation through the intact skull without subject constraint. We found that event-related increases in oxyhemoglobin were evident in localized areas of the occipital cortex of infants aged 2-4 months in response to a brief presentation of a checkerboard pattern reversal while they maintained fixation to attention-grabbing stimuli. The dynamic change in cerebral blood oxygenation was qualitatively similar to that observed in the adult brain. This result introduces near-infrared optical topography as a method for investigating the functional development of the brain in early infancy.

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The complete nucleotide sequence of pETB, a 38.2-kb Staphylococcus aureus plasmid encoding the exfoliative toxin B (ETB), was determined. A total of 50 open reading frames were identified on the plasmid genome and, among these, 32 showed sequence similarity to known proteins. pETB contains three copies of IS257, which divide the pETB genome into three regions: (i) a cadmium resistance operon-containing region, (ii) a lantibiotic production gene-containing region, and (iii) the remaining part where genes for plasmid replication and/or maintenance are dispersed. In the third region, genes of various kinds of functions are present among the replication-and maintenance-related genes. They include two virulence-related genes, the etb gene and a gene encoding a novel ADP-ribosyltransferase closely related to EDIN, which belongs to the C3 family of ADPribosyltransferases modifying Rho GTPases. They also include genes for a cell wall-anchoring surface protein and a phage resistance protein. Based on the determined sequence of pETB, the genome structures of etb-bearing plasmids (ETB plasmids) from various clinical isolates were analyzed by the PCR scanning method. The data indicate that, although the ETB plasmids are highly heterogeneous in genome size, the fundamental genome organization is well conserved. The size variation of the plasmid is mainly attributed to defined regions which may be hot spots for gene shuffling.Exfoliative toxin (ET) is an exotoxin produced by staphylococcal species, causing blisters in human and animal skin (29). ET-producing Staphylococcus aureus is involved in staphylococcal scalded-skin syndrome (SSSS), or Ritter disease, and bullous impetigo in neonates (18,29,32). Serologically, ETs causing diseases in human have been divided into two major serotypes: ETA and ETB (5, 28). Both types cause intraepidermal cleavage in the granular layer, without epidermal necrolysis or inflammatory response of skin (5,16,28). The mechanism whereby ETs produce exfoliation of the skin has been unknown for a long time, but several lines of evidence have suggested that they are acting as a protease: (i) amino acid sequences of ETA and ETB show similarity with the S. aureus V8 serine protease (14), and the catalytic site of V8 protease is conserved in ETA (6); (ii) partially purified ETs preincubated with serine protease inhibitors exhibits delayed skin exfoliation (14); (iii) substitution of the serine residue with glycine in the putative catalytic site of ETA completely abolishes the exfoliative activity of the toxin (37, 38); and (iv) crystal structures of ETA (12, 56) and ETB (55) have recently been determined, and both types were shown to structurally belong to the chymotrypsin family of serine proteases. More recently, it has been shown that ETA digests desmoglein I, which is one of the major desmosome proteins present in the epidermal layer of human skin (4).The genes for ETs are detected only in some S. aureus clinical strains. This limited distribution of the ET genes suggested that certain S. aureus str...

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