• 한국세라믹학회지
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• 제27권8호
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• pp.971-978
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• 1990

The ifluence of transformability and stabilized effects in tetragonal phase on the isothermal phase transformation of Y-TZP at low temperature were investigated. The transformability of Y-TZP powders were gradually increased with calcination temeprature and reached maximum at critical temperature, but when the Y-TZP powders were calcined above critical temperature, transformability of Y-TZP were gradually decreased with increasing calcination temperature. It was concluded that maximum transformability was appeared because particle size effects decreased and constrain effects increased with calcined temperature. The isothermal phase transformation during aging at 25$0^{\circ}C$ only observed in Y-TZP stabilized by constrain effects and the amounts of transformation during aging at 25$0^{\circ}C$ only observed in Y-TZP stabilized by constrain effects and the amount of transformed monoclinic phase during aging decreased with increasing constrain effects. From these results, the mechanism of isothermal phase transformation and degradation behaviors at low temperature in Y-TZP was concluded that occurred by decreasing of constrain effects due to stress relaxation at grian boundary.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
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• pp.117-138
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• 2003

Reactive oxygen species are capable of damaging biomolecules such as lipids, proteins, and DNA, which can not only lead to various diseases, but also oxidative damage resulting aging. In our previous study, Cercis chinensis (Leguminosae) showed a potent antioxidant activity. Nineteen compounds were isolated through antioxidant activity-guided fractionation. The C. chinensis extract and some of the constituents exhibited a potent antioxidant activity on the free radicals and lipid peroxidation and a notable protective effect on the t-BuOOH induced oxidative damage. In vivo test of skin damage induced by UVB irradiation, the extract of C. chinensis and a constituent, piceatannol, exhibited a significant protective effect. The life-span of the HEK-N/F cells were extended by 1.21-2.12 fold as a result of the continuous administration of 3 $\mu\textrm{g}$/ml of the C. chinensis extract and the active constituents compared to that of the control. These observations were attributed to the inhibitory effect of the C. chinensis extract and its constituents on the age-dependent shortening of the telomere. Thus, C. chinensis was demonstrated to protect the skin cells against oxidative stress and inhibit thereby the cellular aging, followed by expectation as antiaging cosmetic ingredient.

• Elastomers and Composites
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• 제40권2호
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• pp.119-127
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• 2005

고무부품의 신뢰성을 확보하기 위해서 고무재료의 물성파악과 수명평가는 매우 중요하다 하겠다. 본 연구에서는 냉장고 콤프레샤 모터에서 발생되는 소음 및 진동 제어 목적으로 고무마운트에 사용되는 고무재료인 NBR과 EPDM에 대해 상온과 $70^{\circ}C,\;85^{\circ}C,\;100^{\circ}C$에서 75일 동안 노화시킨 상태에서 단축 인장과 이축 인장으로 물성시험을 수행하여 가교밀도, 100% 모듈러스 변화와 응력-변형률 관계를 파악하였다. 또한, 고무소재의 노화수명을 예측하기 위해 가속열 노화시험을 수행하여 시간-온도 환산식인 아레니우스 관계식을 구하였다.

• International Journal of Oral Biology
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• 제49권3호
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• pp.69-78
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• 2024

Sestrin 2 (SESN2) is a member of the sestrin family of stress-induced proteins that negatively regulate aging-associated biological processes. This study aims to investigate the role of SESN2 in regulating the differentiation potential and senescence of mesenchymal stem cells (MSCs) derived from young and elderly donors. Bulk RNA sequencing revealed a common decline in the SESN2 mRNA levels in MSCs from elderly individuals, which was confirmed via reverse transcription-polymerase chain reaction and western blot analyses. SESN2 knockdown in MSCs from young donors resulted in phenotypic changes similar to those in MSCs from elderly donors, including an enhanced expression of senescence and adipogenic markers and diminished expression of osteogenic markers. To confirm the effect of decreased SESN2 expression on osteogenic and adipogenic differentiation, we induced Sesn2 knockdown in mouse bone marrow-derived MSCs. Sesn2 knockdown suppressed the mRNA expression of osteogenic marker genes, alkaline phosphatase activity, and matrix mineralization. Furthermore, Sesn2 knockdown enhanced mRNA expression of the adipogenic marker genes and intracellular lipid accumulation. These results suggest that a decline in SESN2 expression during aging contributes to the shift of MSC differentiation from osteogenic to adipogenic lineage.

• Molecular Medicine Reports
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• 제20권5호
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• pp.4111-4118
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• 2019

The administration of D-galactose triggers brain aging by poorly understood mechanisms. It is generally recognized that D-galactose induces oxidative stress or affects protein modifications via receptors for advanced glycated end products in a variety of species. In the present study, we aimed to investigate the involvement of astrocytes in D-galactose-induced brain aging in vitro. We found that D-galactose treatment significantly suppressed cell viability and induced cellular senescence. In addition, as of the accumulation of senescent cells, we proposed that the senescence-associated secretory phenotype (SASP) can stimulate age-related pathologies and chemoresistance in brain. Consistently, senescent astrocytic CRT cells induced by D-galactose exhibited increases in the levels of IL-6 and IL-8 via NF-κB activation, which are major SASP components and inflammatory cytokines. Conditioned medium prepared from senescent astrocytic CRT cells significantly promoted the viability of brain tumor cells (U373-MG and N2a). Importantly, conditioned medium greatly suppressed the cytotoxicity of U373-MG cells induced by temozolomide, and reduced the protein expression levels of neuron marker neuron-specific class III β-tubulin, but markedly increased the levels of c-Myc in N2a cells. Thus, our findings demonstrated that D-galactose treatment might mimic brain aging, and that D-galactose could contribute to brain inflammation and tumor progression through inducing the accumulation of senescent-secretory astrocytes.

• 생명과학회지
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• 제34권8호
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• pp.594-607
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• 2024

다양한 종류의 플라스틱 제품이 오랫동안 산업 및 생활 제품 분야에서 널리 사용되고 있다. 플라스틱 제품에서 파생된 크기가 작은 플라스틱 입자인 MPs와 NPs는 흡입, 섭취 또는 피부 접촉을 통해 인체 내로 유입될 수 있다. 세포 내 이입을 통해 세포 안으로 들어온 MNPs는 세포의 자가 포식을 활성화할 수 있지만, 리소좀 기능 장애로 인해 자가포식 플럭스가 차단될 수 있다. 나아가 세포질에 축적된 그들은 ROS 생성으로 인한 산화적 스트레스, 미토콘드리아 기능 장애, 염증 반응 증가 등과 같은 다양한 스트레스를 유발할 수 있다. 한편 많은 질병과 연관된 세포 노화는 노화의 특징으로, 세포 손상과 스트레스에 반응하여 세포 주기가 안정적으로 종료되는 것으로 정의된다. 특히 세포 노화 유도의 핵심 인자인 산화적 스트레스의 축적은 주요 노화 표지 인자들이 발현을 유도하고, 노화 세포는 염증성 cytokine과 chemokine을 포함한 SASP의 분비를 증가시킨다. 최근 MNPs에 의한 세포 노화 유도에 대한 관심이 높아지고 있지만, 이들에 의한 세포 노화 개시의 기전 및 치료 표적에 대한 연구는 여전히 부족한 실정이다. 따라서 이 총설에서는 MNPs로 인한 다양한 인체 기관계를 구성하는 주요 세포의 세포 노화 유도에 대한 최근 연구 동향을 파악하는데 중점을 두었으며, 아울러 이를 극복하기 위한 방향을 제시하였다.

• 열처리공학회지
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• 제30권6호
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• pp.279-284
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• 2017

Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

• 한국보건간호학회지
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• 제26권3호
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• pp.440-452
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• 2012

Purpose: The purpose of this study was to provide basic data for use in development of strategy for healthy aging preparation and successful transfer to old age by identifying factors influencing quality of life of the baby boom generation. Methods: The data were collected from a total of 205 members of the baby boom generation(aged 48 to 56), and analysis was performed using descriptive statistics, t-test, ANOVA, Pearson's correlation coefficient, and stepwise multiple regression using the SPSS(Version19.0) program. Results: Burden for taking care of children, aging anxiety, preparations for old age, and quality of life according to the general characteristics and health-related characteristics commonly showed a significant difference in education level and presence of stress. The greater the more burden for taking care of children and the deeper the aging anxiety, the lower the quality of life, and the better prepared for aging, the higher the quality of life. Factors affecting quality of life in the baby boom generation included preparations for old age, burden for taking care of children, monthly household income, and quality of sleep. Explanatory power was 32%. Conclusion: For successful transition to old age and for improvement of quality of life in the baby boom generation, a comprehensive approach in micro and macro dimensions will be sought.

• 대한한의진단학회지
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• 제9권1호
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• pp.59-68
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• 2005

Background and purpose: Cardiovascular disease will undoubtedly rise along with the aging of the 'baby-boom' generation. The purpose of this study is to find the new index of the cardiovascular aging. Methods: The effects of aging on the heart and the arterial system are surveyed in the point of structure and function. Results: Arterial stiffening is due to the fatiguing effects of periodic stress on the arterial wall and is the main reason for increasing pulse wave velocity. The systolic hypertension is caused by the early return of wave reflection. The increased after-load by the arterial change leads to the development of left ventricular hypertrophy. The reduction in left ventricular compliance cause the impairments of the diastolic function. In contrast to the lower limb, aging effect in the upper limb are almost due to the ascending aortic pressure wave and the reflected wave from the lower limb. Conclusion: We have the following points. (1) The change of physiological pulse pattern by age can be explained by the early returning of reflected wave. (2) The atrial pulse in old age are generated by the left ventricular hypertrophy.

• Preventive Nutrition and Food Science
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• 제19권3호
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• pp.178-186
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• 2014

Many recent studies have focused on maintaining a healthy life by preventing and/or postponing the aging process. Numerous studies have reported that continuous exposure to reactive oxygen species can stimulate skin aging and that excessive accumulation of fat can cause an impaired skin barrier and tissue structure alterations. Thus, the maintenance of antioxidant homeostasis and the suppression of adipose accumulation are important strategies for skin anti-aging. Here, we prepared three types of extracts [whole juice, acetone-perchloric acid (PCA), and ethanol] from 20 fruits and medicinal herbs native to the Gyeongnam area of Korea. The total phenolic content of each extract was analyzed, and we observed higher total phenolic contents in the medicinal herbs. Consistent with this, the results of the oxygen radical absorbance activity capacity assay indicated that the in vitro antioxidant activities of the medicinal herb extracts were stronger than those of the fruit extracts. The fruits and medicinal herbs had strong effects on cell-based systems, including $H_2O_2$-induced oxidative stress in human keratinocytes and 3T3-L1 lipid accumulation. Nishimura Wase persimmon, Taishu persimmon, wrinkled giant hyssop, sweet wormwood, Chinese cedar, red perilla, tan shen, hiyodori-jogo, and cramp bark may be natural anti-aging materials with effective antioxidant and anti-adipogenic activities. Taken together, our findings may provide scientific evidence supporting the development of functional foods and nutraceuticals from fruits and medicinal herbs.