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Biomedical subjects

Jae H Kim

Publications and source records attributed to Jae H Kim.

6 recordsLinked to original sources
PubMed2006

The characteristics of tropospheric ozone seasonality observed from ozone soundings at Pohang, Korea.

This paper presents the first analysis of vertical ozone sounding measurements over Pohang, Korea. The main focus is to analyze the seasonal variation of vertical ozone profiles and determine the mechanisms controlling ozone seasonality. The maxima ozone at the surface and in the free troposphere are observed in May and June, respectively. In comparison with the ozone seasonality at Oki (near sea level) and Happo (altitude of 1840 m) in Japan, which are located at the same latitude as of Pohang, we have found that the time of the ozone maximum at the Japanese sites is always a month earlier than at Pohang. Analysis of the wind flow at the surface shows that the wind shifts from westerly to southerly in May over Japan, but in June over Pohang. However, this wind shift above boundary layer occurs a month later. This wind shift results in significantly smaller amounts of ozone because the southerly wind brings clean wet tropical air. It has been suggested that the spring ozone maximum in the lower troposphere is due to polluted air transported from China. However, an enhanced ozone amount over the free troposphere in June appears to have a different origin. A tongue-like structure in the time-height cross-section of ozone concentrations, which starts from the stratosphere and extends to the middle troposphere, suggests that the ozone enhancement occurs due to a gradual migration of ozone from the stratosphere. The high frequency of dry air with elevated ozone concentrations in the upper troposphere in June suggests that the air is transported from the stratosphere. HYSPLIT trajectory analysis supports the hypothesis that enhanced ozone in the free troposphere is not likely due to transport from sources of anthropogenic activity.

Atmosphere↗
PubMed2005

Gli3 null mice display glandular overgrowth of the developing stomach.

The role of the Hedgehog signaling pathway in various aspects of gut development is still poorly understood. In the developing stomach, Sonic (Shh) and Indian (Ihh) hedgehog are expressed in both distinct and overlapping regions. Loss of Sonic hedgehog function in the stomach results in a glandular phenotype of intestinal transformation and overgrowth. These changes are reminiscent of the pre-malignant lesion, intestinal metaplasia. To determine the role of Hedgehog-related transcription factors, Gli2 and Gli3, in Shh signaling during stomach development, we conducted a mutant analysis of glandular stomach from Shh, Gli2, and Gli3 mutant mice. Although Gli2 principally mediates the activator function of Shh, surprisingly we observed minimal changes in glandular development in the Gli2 mutant stomach. Furthermore, Gli3, which typically functions as a repressor of Hedgehog signal, showed a striking phenocopy of the glandular expansion and intestinal transformation found in Shh mutant stomach. A reduction in apoptotic events was seen in all mutant stomachs with no appreciable changes in proliferation. Both Shh and Gli3 mutant stomachs displayed early changes of intestinal transformation but these did not impact on the overall differentiation of the gastric epithelium. Interestingly, the observation that Gli3 shares a similar glandular phenotype to Shh mutant stomach reveals a possible novel role of Gli3 activator in the developing stomach. The embryonic stomach is a unique model of the Hedgehog pathway function and one that may help to uncover some of the mechanisms underlying the development of intestinal metaplasia.

Animals↗
PubMed2005

Neonatal short bowel syndrome: a cohort study.

BACKGROUND: To date, our knowledge of morbidity and mortality in neonatal short bowel syndrome (SBS) is based on individual case series. Shortcomings of the published literature include long patient recruitment time, selection bias, variable SBS definitions, failure to account for gestational age, and incomplete follow-up. By applying more rigorous methodology, our aim was to determine outcomes of SBS neonates compared with a control group of neonates without SBS. METHODS: A cohort study of all neonates with abdominal pathology requiring laparotomy between January 1, 1997, and December 31, 1998, with observation through July 1, 2001. Short bowel syndrome was defined as patients requiring parenteral nutrition for more than 42 days or residual small bowel length of less than 25% predicted by gestational age. Student's t test, Mann-Whitney U test, and chi2 were used where appropriate. Kaplan-Meier curves were used to determine cumulative survival. Covariates important in the development of SBS were examined using forward step-wise logistic regression. RESULTS: There were 175 patients (with SBS = 40, without SBS = 135) with a mean gestational age of 30.7 +/- 4.6 weeks vs 35.9 +/- 4.8 weeks, respectively (P < .0005). The patients with SBS suffered significantly more morbidity than the group without SBS in all categories of investigation (surgical complications, septic events, central venous line complications, duration to adaptation and parenteral nutrition independence, cholestasis and liver failure, and duration of hospitalization). The case fatality rate was 37.5% in patients with SBS vs 13.3% in patients without SBS (P = .001). Most of the deaths were caused by liver failure or sepsis and occurred within 1 year from the date of surgery. Presence of an ileostomy (exp(B) = 12.29; P < .0005) and a residual small bowel length less than 50% of the original length (exp(B) = 26.84; P < .0005) were the only 2 variables in a logistic regression analysis found to be independently associated with the development of SBS. CONCLUSION: This cohort study clearly illustrates the tremendous morbidity experienced by infants with SBS relative to other surgical neonates. Accurate estimates of the morbidity associated with SBS enables clinicians to appropriately counsel parents, allocate resources and initiate therapeutic trials.

Cholestasis↗
PubMed2004

Salmonella gallinarum gyrA mutations associated with fluoroquinolone resistance.

Salmonella enterica subsp. enterica serovar Gallinarum (S. gallinarum) is the causative organism of fowl typhoid, and an outbreak of fowl typhoid in Korea was confirmed in 1992. The aim of this study was to investigate possible changes in fluoroquinolone susceptibility among S. gallinarum isolates from 1995 to 2001, and to analyse mutations of the gyrA gene in fluoroquinolone-resistant isolates. Among 258 S. gallinarum isolates tested by the disk diffusion method, isolates from 1995 (n=18) were susceptible to all fluoroquinolones tested, whereas a number of isolates from 2001 (n=46) showed reduced susceptibility to enrofloxacin (6.5%), ciprofloxacin (10.9%), norfloxacin (52.5%) and ofloxacin (82.6%). The minimum inhibitory concentration range of enrofloxacin, ciprofloxacin, norfloxacin, ofloxacin and danofloxacin increased from < or =0.06 approximately 0.25 microg/ml in 1995 to 2 approximately 8 microg/ml in 2001. When amino acid changes in the gyrA were analysed by DNA sequencing, 22.5% and 14.7% among 258 isolates had a mutation at the Ser-83 and Asp-87 codons, respectively, and the prevalence of these mutants increased from 5.6% in 1995 to 89.1% in 2001. These mutants contained a change from Ser to Phe or Tyr at codon 83, or a change from Asp to Gly, Tyr or Asn at codon 87, and showed a range of minimum inhibitory concentrations of enrofloxacin from 0.5 to 8 microg/ml, ciprofloxacin from 0.25 to 4 microg/ml, norfloxacin from 2 to 32 microg/ml, ofloxacin from 0.5 to 4 microg/ml, and danofloxacin from 0.5 to 4 microg/ml. These results suggested an important association between the gyrA mutations and fluoroquinolone resistance of S. gallinarum.

Amino Acid Sequence↗
PubMed2002

Dosimetric characteristics of Novalis shaped beam surgery unit.

The dosimetric characteristics of a new dedicated radiosurgical treatment unit are systematically measured in terms of its percent depth dose, beam profile, and relative scatter factor. High-resolution diode detector, mini-ion-chamber detector, and conventional Kodak XV films are used to measure dosimetric data for a range of field sizes from 6x6 mm to 100x100 mm. The effects of collimator size, micro-multileaf collimator shape, and detector type on the dosimetric data are investigated. Results indicate that, with careful design, accurate dosimetric data could be acquired using either a dedicated diode detector or a mini-ion-chamber detector, and film detector. Special attention is required when measuring dosimetric data for small field sizes such as 6x6 mm.

Equipment Failure Analysis↗