Skip Navigation
Skip to contents

PHRP : Osong Public Health and Research Perspectives

OPEN ACCESS
SEARCH
Search

Search

Page Path
HOME > Search
7 "stability"
Filter
Filter
Article category
Keywords
Publication year
Authors
Original Articles
Instability of Plasma and Serum Progastrin-Releasing Peptide During Repeated Freezing and Thawing
Jae-Eun Lee, Jin-Hyun Lee, Maria Hong, Seul-Ki Park, Ji-In Yu, So-Youn Shin, Shine Young Kim
Osong Public Health Res Perspect. 2016;7(6):351-355.   Published online December 31, 2016
DOI: https://doi.org/10.1016/j.phrp.2016.11.004
  • 1,945 View
  • 19 Download
  • 2 Citations
AbstractAbstract PDF
Objectives
Progastrin-releasing peptide (proGRP) is a promising biomarker for small cell lung cancer. However, not much is known about how sample processing and storage conditions affect the stability of proGRP. Here, we examined the effects of repeated freeze–thaw cycles on the stability of proGRP in plasma and serum.
Methods
Concentrations of proGRP were measured in plasma and serum samples exposed to two, three, or four freeze–thaw cycles and these were compared with values of corresponding samples exposed to one cycle (baseline). We also performed the area under the receiver-operating-characteristic curve (AUC) analysis to determine whether the differences of proGRP concentrations between each paired plasma and serum sample (ΔproGRP) can be used for identifying the samples that have been exposed to multiple freeze–thaw cycles.
Results
Concentrations of proGRP gradually decreased in both plasma and serum samples with increasing numbers of freeze–thaw cycles. Reduction rates of proGRP concentrations were greater in serum than in plasma samples and serum proGRP levels declined with statistical significance (p < 0.001) up to 10.1% after four freeze–thaw cycles. The ΔproGRP measurement showed fair accuracy (AUC = 0.741) for identifying samples that had been through four freeze–thaw cycles. The sensitivity was 82.8% and specificity was 62.1% at an optimal cut-off point of > 4.9.
Conclusion
Our study shows that the stability of circulating proGRP is affected in both plasma and serum samples by repeated freezing and thawing. We also show that ΔproGRP could be used for identifying paired plasma and serum samples subjected to multiple freeze–thaw cycles.
Influence of Obesity on Postural Stability in Young Adults
Sung Min Son
Osong Public Health Res Perspect. 2016;7(6):378-381.   Published online December 31, 2016
DOI: https://doi.org/10.1016/j.phrp.2016.10.001
  • 1,722 View
  • 17 Download
  • 18 Citations
AbstractAbstract PDF
Objectives
The purpose of this study was to determine whether obesity is associated with less postural stability in young adults, and whether it is influenced by anterior pelvic tilt angle and sensory dysfunction.
Methods
Center of gravity (COG) velocity and total sway distance with eyes open or eyes closed on firm or foam floors were determined in 12 obese individuals and 12 individuals with normal weight.
Results
On firm and foam floors with eyes closed, center of gravity velocity and total sway distance were significantly greater in the obese group than in the normal-weight group. However, on firm and foam floors with eyes open, center of gravity velocity and total sway distance were not significantly different in the two groups.
Conclusion
The clinical implication of our findings is that obese young adults exhibit poor postural stability. Our findings also suggested that postural instability in obese individuals is associated with increased lordosis due to abdominal fat and poor integration of plantar somatosensory input.
Inorganic Phosphorus and Potassium Are Putative Indicators of Delayed Separation of Whole Blood
Jae-Eun Lee, Maria Hong, Seul-Ki Park, Ji-In Yu, Jin-Sook Wang, Haewon Shin, Jong-Wan Kim, Bok-Ghee Han, So-Youn Shin
Osong Public Health Res Perspect. 2016;7(2):90-95.   Published online April 30, 2016
DOI: https://doi.org/10.1016/j.phrp.2015.11.003
  • 1,643 View
  • 15 Download
  • 6 Citations
AbstractAbstract PDF
Objectives
The delayed separation of whole blood can influence the concentrations of circulating blood components, including metabolites and cytokines. The aim of this study was to determine whether clinical-biochemistry analytes can be used to assess the delayed separation of whole blood.
Methods
We investigated the plasma and serum concentrations of five clinical-biochemistry analytes and free hemoglobin when the centrifugation of whole blood stored at 4°C or room temperature was delayed for 4 hours, 6 hours, 24 hours, or 48 hours, and compared the values with those of matched samples that had been centrifuged within 2 hours after whole-blood collection.
Results
The inorganic phosphorus (IP) levels in the plasma and serum samples were elevated ≥ 1.5-fold when whole-blood centrifugation was delayed at room temperature for 48 hours. Furthermore, the IP levels in the plasma samples showed excellent assessment accuracy [area under the receiver-operating-characteristic curve (AUC) > 0.9] after a 48-hour delay in whole-blood separation, and high sensitivity (100%) and specificity (95%) at an optimal cutoff point. The IP levels in the serum samples also exhibited good assessment accuracy (AUC > 0.8), and high sensitivity (81%) and specificity (100%). The potassium (K+) levels were elevated 1.4-fold in the serum samples following a 48-hour delay in whole-blood separation. The K+ levels showed excellent assessment accuracy (AUC > 0.9) following a 48-hour delay in whole-blood separation, and high sensitivity (95%) and specificity (91%) at an optimal cutoff point.
Conclusion
Our study showed that the IP and K+ levels in the plasma or serum samples could be considered as putative indicators to determine whether whole-blood separation had been delayed for extended periods.
Modeling the Spread of Ebola
Tae Sug Do, Young S. Lee
Osong Public Health Res Perspect. 2016;7(1):43-48.   Published online February 28, 2016
DOI: https://doi.org/10.1016/j.phrp.2015.12.012
  • 1,740 View
  • 17 Download
  • 12 Citations
AbstractAbstract PDF
Objectives
This study aims to create a mathematical model to better understand the spread of Ebola, the mathematical dynamics of the disease, and preventative behaviors.
Methods
An epidemiological model is created with a system of nonlinear differential equations, and the model examines the disease transmission dynamics with isolation through stability analysis. All parameters are approximated, and results are also exploited by simulations. Sensitivity analysis is used to discuss the effect of intervention strategies.
Results
The system has only one equilibrium point, which is the disease-free state (S,L,I,R,D) = (N,0,0,0,0). If traditional burials of Ebola victims are allowed, the possible end state is never stable. Provided that safe burial practices with no traditional rituals are followed, the endemic-free state is stable if the basic reproductive number, R0, is less than 1. Model behaviors correspond to empirical facts. The model simulation agrees with the data of the Nigeria outbreak in 2004: 12 recoveries, eight deaths, Ebola free in about 3 months, and an R0 value of about 2.6 initially, which signifies swift spread of the infection. The best way to reduce R0 is achieving the speedy net effect of intervention strategies. One day's delay in full compliance with building rings around the virus with isolation, close observation, and clear education may double the number of infected cases.
Conclusion
The model can predict the total number of infected cases, number of deaths, and duration of outbreaks among others. The model can be used to better understand the spread of Ebola, educate about prophylactic behaviors, and develop strategies that alter environment to achieve a disease-free state. A future work is to incorporate vaccination in the model when the vaccines are developed and the effects of vaccines are known better.
Effect of Repeated Freezing and Thawing on Biomarker Stability in Plasma and Serum Samples
Jae-Eun Lee, Shine Young Kim, So-Youn Shin
Osong Public Health Res Perspect. 2015;6(6):357-362.   Published online December 31, 2015
DOI: https://doi.org/10.1016/j.phrp.2015.11.005
  • 1,815 View
  • 16 Download
  • 37 Citations
AbstractAbstract PDF
Objectives
The stability of circulating proteins can be affected by repeated freezing and thawing. The aim of our study was to identify the effect of repeated freezing and thawing on the plasma and serum concentrations of eight proteins [interferon-γ, interleukin (IL)-8, IL-15, IL-17A, matrix metalloproteinase (MMP)-7, tumor necrosis factor-α, vascular endothelial growth factor (VEGF), and VEGF receptor 2 (VEGF-R2)].
Methods
We assessed the concentration changes of these proteins in 30 plasma and serum samples subjected to three, four, or five freeze–thaw cycles, and compared these with the concentration changes in the samples that were subjected to two freeze–thaw cycles before analysis.
Results
Repeated freezing and thawing by up to five cycles did not modify the plasma and serum concentrations of interferon-γ, IL-8, and VEGF-R2, while levels of MMP-7, tumor necrosis factor-α, and VEGF were significantly changed in both plasma and serum samples. Moreover, MMP-7 and VEGF concentrations tended to increase with freeze–thaw cycles. They were more elevated in plasma samples (up to about 15%) than in serum samples (up to about 7%), suggesting that serum is the preferred sample type for the analysis of circulating proteins.
Conclusion
This is the first report on the effect of repeated freezing and thawing on plasma concentrations of MMP-7 and VEGF-R2. Our findings propose that researchers should consider the number of freeze–thaw cycles to select plasma or serum samples, depending on the type of analyte.
A Differential Equation Model for the Dynamics of Youth Gambling
Tae Sug Do, Young S. Lee
Osong Public Health Res Perspect. 2014;5(4):233-241.   Published online August 31, 2014
DOI: https://doi.org/10.1016/j.phrp.2014.06.008
  • 1,838 View
  • 12 Download
  • 6 Citations
AbstractAbstract PDF
Objectives
We examine the dynamics of gambling among young people aged 16–24 years, how prevalence rates of at-risk gambling and problem gambling change as adolescents enter young adulthood, and prevention and control strategies.
Methods
A simple epidemiological model is created using ordinary nonlinear differential equations, and a threshold condition that spreads gambling is identified through stability analysis. We estimate all the model parameters using a longitudinal prevalence study by Winters, Stinchfield, and Botzet to run numerical simulations. Parameters to which the system is most sensitive are isolated using sensitivity analysis.
Results
Problem gambling is endemic among young people, with a steady prevalence of approximately 4–5%. The prevalence of problem gambling is lower in young adults aged 18–24 years than in adolescents aged 16–18 years. At-risk gambling among young adults has increased. The parameters to which the system is most sensitive correspond to primary prevention.
Conclusion
Prevention and control strategies for gambling should involve school education. A mathematical model that includes the effect of early exposure to gambling would be helpful if a longitudinal study can provide data in the future.
A Note on Obesity as Epidemic in Korea
Mun Seok Kim, Chaeshin Chu, Yongkuk Kim
Osong Public Health Res Perspect. 2011;2(2):135-140.   Published online June 30, 2011
DOI: https://doi.org/10.1016/j.phrp.2011.08.004
  • 1,681 View
  • 13 Download
  • 9 Citations
AbstractAbstract PDF
Objective To analyze the incidence of obesity in adults aged 19–59 years in Korea and predict its trend in the future.
Methods
We considered a two-compartmental deterministic mathematical model Susceptible-Infected-Susceptible (SIS), a system of difference equations, to predict the evolution of obesity in the population and to propose strategies to reduce its incidence.
Results
The prevention strategy on normal-weight individuals produced a greater improvement than that produced by treatment strategies.
Conclusions
Mathematical model sensitivity analysis suggests that obesity prevention strategies are more effective than obesity treatment strategies in controlling the increase of adult obesity in Korea.

PHRP : Osong Public Health and Research Perspectives