SUBJECTS AND METHODS: Participants were 99 normal, healthy, full-term newborn babies with chronological age between 11 and 128 hours of age (mean=46.73, standard deviation=26.36). A cross-sectional study design was used to measure WBA at 16 one-third octave frequency points from 99 neonates comprising of three ethnic groups: Malays (n=58), Chinese (n=13) and Indians (n=28). A total of 165 ears (83.3%) that passed a battery of tests involving distortion product otoacoustic emissions, 1 kHz tympanometry and acoustic stapedial reflex were further tested using WBA. Moreover, body size measurements were recorded from each participant.
RESULTS: The Malays and Indians neonates showed almost identical WBA response across the frequency range while the Chinese babies showed lower absorbance values between 1.25 kHz and 5 kHz. However, the differences observed in WBA between the three ethnic groups were not statistically significant (p=0.23). Additionally, there were no statistically significant difference in birth weight, height and head circumference among the three ethnic groups.
CONCLUSIONS: This study showed that Malays, Chinese and Indians neonates were not significantly different in their WBA responses. In conclusion, to apply for the ethnic-specific norms is not warranted when testing neonates from population constitute of these three ethnicities.
DESIGN: Forty-four full-term healthy neonates (17 males and 27 females) participated in a longitudinal study. The neonates were assessed at 1-month intervals from 0 to 6 months of age using high-frequency tympanometry, acoustic stapedial reflex, distortion product otoacoustic emissions, and pressurized WBA. The values of WBA at tympanometric peak pressure (TPP) and 0 daPa across the frequencies from 0.25 to 8 kHz were analyzed as a function of age.
RESULTS: A linear mixed model analysis, applied to the data, revealed significantly different WBA patterns among the age groups. In general, WBA measured at TPP and 0 daPa decreased at low frequencies (<0.4 kHz) and increased at high frequencies (2 to 5and 8 kHz) with age. Specifically, WBA measured at TPP and 0 daPa in 3- to 6-month-olds was significantly different from that of 0- to 2-month-olds at low (0.25 to 0.31 kHz) and high (2 to 5 and 8 kHz) frequencies. However, there were no significant differences between WBA measured at TPP and 0 daPa for infants from 3 to 6 months of age.
CONCLUSIONS: The present study provided clear evidence of maturation of the outer and middle ear system in healthy infants from birth to 6 months. Therefore, age-specific normative data of pressurized WBA are warranted.
Method: Participants of this cross-sectional study included 99 full-term neonates (165 ears) with mean chronological age of 46.7 hrs (SD = 26.3 hrs). Of the 99 neonates, 58 were Malay, 28 were Indian, and 13 were Chinese. The neonates who passed high-frequency (1 kHz) tympanometry, acoustic stapedial reflex, and distortion product otoacoustic emission screening tests were assessed using a pressurized WBA test (wideband tympanometry). To reduce the number of measurement points, the WBA responses were averaged to 16 one-third octave frequency bands from 0.25 to 8 kHz. A mixed-model analysis of variance was applied to the data to investigate the effects of frequency, ear, gender, and ethnicity on WBA. The analysis of variance was also used to compare between WBA measured at TPP and 0 daPa. An interclass correlation coefficient test was applied at each of the 16 frequency bands to measure the test-retest reliability of WBA at TPP and 0 daPa.
Results: Both WBA measurements at TPP and 0 daPa exhibited a multipeaked pattern with 2 maxima at 1.25-1.6 kHz and 6.3 kHz and 2 minima at 0.5 and 4 kHz. The mean WBA measured at TPP was significantly higher than that measured at 0 daPa at 0.25, 0.4, 0.5, 1.25, and 1.6 kHz only. A normative data set was developed for absorbance at TPP and at 0 daPa. There was no significant effect of ethnicity, gender, and ear on both measurements of WBA. The test-retest reliability of WBA at TPP and 0 daPa was high with the interclass correlation coefficient ranging from 0.77 to 0.97 across the frequencies.
Conclusions: Normative data of WBA measured at TPP and 0 daPa for neonates were provided in the present study. Although WBA at TPP was slightly higher than the WBA measured at 0 daPa at some frequencies below 2 kHz, the WBA patterns of the 2 measurements were nearly identical. Moreover, the test-retest reliability of both WBA measurements was high.
OBJECTIVES: In this study, the xylC gene from Rhodococcus ruber UKMP-5M was expressed in Escherichia coli, purified, and characterized.
MATERIALS AND METHODS: The xylC was amplified and cloned in E. coli. The recombinant plasmid pGEMT-xylC was digested by NdeI and HindIII to construct plasmid pET28b-xylC and transformed in E. coli BL21 (DE3). Expression of the recombinant protein was induced by 1 mM isopropyl β-D-thiogalactoside (IPTG) at 37°C. The BZDH was purified by ion exchange chromatography, in which the product was an NAD-dependent enzyme using benzaldehyde as a substrate for enzyme characterization. The end metabolite was identified via gas chromatography mass spectrometry (GC-MS).
RESULTS: The recombinant BZDH is 27 kDa, purified by ion exchange chromatography. The activity of BZDH was 9.4 U.μL-1 The optimum pH and temperature were 8.5 and 25ºC, respectively. The Michaelis constant (Km) and maximum velocity (Vmax) were 4.2 mM and 19.7 U.mL-1, respectively. The metabolite of BZDH was benzene carboxylic acid as determined by GC-MS analysis.
CONCLUSIONS: BZDH has the ability to degrade benzaldehyde to less toxic compounds. The BZDH is a critical enzyme for the degradation of aromatic hydrocarbons in Rhodococcus sp. The BZDH from R. ruber UKMP-5M is showed similar function with other aldehyde dehydrogenases.