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Biomedical subjects

Kyoko Hirasawa

Publications and source records attributed to Kyoko Hirasawa.

9 recordsLinked to original sources
PubMed2006

Surveillance of group B streptococcal toxic shock-like syndrome in nonpregnant adults and characterization of the strains in Japan.

Nine group B streptococci (GBS) strains were isolated from five toxic shock-like syndrome cases of nonpregnant adults in Japan from 2001 to 2005. All of them were identified as Streptococcus agalactiae. The serotypes of these strains were Ib, III, V, and VII. Pulsed-field gel electrophoresis revealed that the patterns of the strains isolated from the different patients were variable. Antimicrobial susceptibility tests showed that all of the strains were susceptible to penicillin G, ampicillin, cefotaxime, clindamycin, and telithromycin. One strain showed intermediate resistance to erythromycin.

Aged↗
PubMed2005

Molecular mechanisms of high level tetracycline-resistance in group A streptococcal isolates, T serotypes 4 and 11.

The molecular mechanism of high level tetracycline resistance in T serotypes 4 and 11 group A streptococcal (GAS) isolates was examined in 61 tetracycline-resistant isolates in Japan. PCR and sequencing analyses revealed that the T serotype/emm genotype, T4/4 isolates carried tet(O) genes, which were genetically homogenous. The T11/11 and T11/89 isolates carried different subtypes of tet(M) genes, which were present on transposons Tn916 and Tn1545, respectively. In addition, these T11 isolates may have obtained the tet(M) gene after the 1990s, because resistance to tetracycline in T11 isolates was rarely found before then. These results strongly suggested that the T4 and T11 GAS isolates acquired tetracycline-resistance via different molecular mechanisms.

Bacterial Proteins↗
PubMed2005

Close correlation of streptococcal DNase B (sdaB) alleles with emm genotypes in Streptococcus pyogenes.

DNase B is a major nuclease and a possible virulence factor in Streptococcus pyogenes. The allelic diversity of streptococcal DNase B (sdaB) gene was investigated in 83 strains with 14 emm genotypes. Of the 15 alleles identified, 11 alleles carried only synonymous nucleotide substitutions. On the other hand, 4 alleles had a non-synonymous substitution other than synonymous substitutions, resulting in the substitution of a single amino acid. The distribution of each allele was generally emm genotype-specific. Only sdaB7 was found in both emm2 and emm4. The promoter region was highly conserved and DNase B protein was similarly expressed in all alleles.

Alleles↗
PubMed2005

Antimicrobial susceptibility survey of Streptococcus pyogenes isolated in Japan from patients with severe invasive group A streptococcal infections.

We assessed antimicrobial susceptibility against 211 Streptococcus pyogenes strains isolated from patients with severe invasive group A streptococcal infections. Overall, 3.8, 1.4, 1.4, and 0.5% of the isolates were resistant to erythromycin, clindamycin, telithromycin, and ciprofloxacin, respectively, and 10.4% had intermediate resistance to ciprofloxacin. All isolates were susceptible to ampicillin and cefotaxime.

Anti-Bacterial Agents↗
PubMed2003

Hemodynamic responses to visual stimulation in occipital and frontal cortex of newborn infants: a near-infrared optical topography study.

A near-infrared optical topography (OT) was used to reveal spatio-temporal changes in the cerebral oxygenation of newborn infants in response to brief visual stimulation. Newborn infants were presented 3-s stroboscopic light flashing at 14 Hz during spontaneous sleep. Event-related changes in oxy- and deoxyhemoglobin ([oxy-Hb] and [deoxy-Hb]) were observed over the occipital and frontal cortex. The visual stimulus produced statistically significant increases in oxyhemoglobin not only in the occipital cortex but also in the prefrontal cortex. These results suggest that the cerebrovascular coupling is already functioning in newborn's brain. The prefrontal activation implies that it may contribute to early processing of sensory signals.

Cerebrovascular Circulation↗
PubMed2002

Functional brain imaging using fMRI and optical topography in infancy.

We performed functional magnetic resonance imaging and optical topography over the visual cortex of subjects during sedation with pentobarbital, and 8-Hz flickering light was intermittently projected onto their eyelids. Two age groups were analyzed: infants <60 days old and those >60 days old (corrected for gestational age at birth). The stimulus-related signal change was positive in the lateral geniculate nucleus regardless of the infant's age, but it reversed in the primary visual cortex from positive in the infants less than 60 days old to negative in the infants more than 60 days old (Experiment 1). We also investigated spontaneous changes in the cerebral oxygenation state of neonates and infants aged 1 month during quiet sleeping by using a form of multi-channel near-infrared spectroscopy: non-invasive optical topography. Spatially synchronized oscillations of changes in the concentration of oxy-hemoglobin (oxy-Hb) and deoxy-Hb were observed throughout the occipital cortex in neonates but not in the infants aged 1 month. Time series analysis based on the theory of non-linear oscillations showed that the mean periods of the oscillation for each infant ranged from 11 to 18s. The phase lag of oxy-Hb relative to deoxy-Hb was stable at about 3 pi/4 in neonates but in the infant aged 1 month, time lag was unstable. These findings may be due to rapid synaptogenesis in early life.

Journal Article↗
PubMed2002

The relationship between mismatch negativity and arousal level. Can mismatch negativity be an index for evaluating the arousal level in infants?

BACKGROUND: Electrophysiological and behavioral studies have shown that stimulus relevance contributes to auditory processing in sleep and auditory stimuli changes the sleep stages. So we observed changes in auditory processing due to sleep stages by recording infant mismatch negativity (MMN) during different states and investigated the arousal mechanisms. METHODS: Auditory event-related potentials (ERPs) of 26 neonates were recorded using high-density EGI EEG system. Stimuli consisted of 1000 Hz tones with 90% probability as standard and 1200 Hz with 10% probability as deviant. Study 1 was designed for the confirmation of the recording of MMN from neonates and Study 2 for investigating whether an appropriate stimulus onset asynchrony (SOA) of the stimulus would induce a clear difference in the latency or amplitude. RESULTS: (Study 1) MMN were obtained from all subjects. No differences of the latencies, amplitudes and distribution due to arousal or sleep stage were observed. After the MMN response occurred, a prominent negativity like Nc was seen in response to deviant stimuli in active sleep and waking state. (Study 2) No distinct differences between the difference states were seen in any SOA. CONCLUSIONS: Only MMN did not characterize the arousal or sleep stage. But the modality of the auditory evoked potentials (AEPs) may differ according to the state, so further detailed investigation could enable the detection of the infants' state using the AEP.

Journal Article↗