Shinhae Lee

Insects as a model system for aging studies

As the human lifespan has increased dramatically in recent decades, the amount of aging research has correspondingly increased. To investigate mechanisms of aging, an efficient model system is required. Although mammalian animal models are essential for aging studies, they are sometimes inappropriate due to their long lifespans and high maintenance costs. In this regard, insects can be effective alternative model systems for aging studies, as insects have a relatively short lifespan and cost less to maintain. Many species of insects have been used as model systems for aging studies, especially fruit flies, silkworm moths and several social insects. Fruit flies are most commonly used for aging studies due to the wide availability of abundant resources such as mutant stocks, databases and genetic tools. Silkworm moths are also good tools for studying aging at the tissue level due to their relatively large size. Last, social insects such as ants and bees are good for investigating lifespan determinants, as their lifespans significantly differ according to caste despite a constant genotype among the population. In this review, we discuss the current status and future prospects of aging research using insect model systems.

Effects of Essential Oil from Hinoki Cypress, Chamaecyparis obtusa, on Physiology and Behavior of Flies

Phytoncides, which are volatile substances emitted from plants for protection against plant pathogens and insects, are known to have insecticidal, antimicrobial, and antifungal activities. In contrast to their negative effects on microorganisms and insects, phytoncides have been shown to have beneficial effects on human health. Essential oil from Hinoki cypress (Chamaecyparis obtusa) is mostly used in commercial products such as air purifiers. However, the physiological/behavioral impact of essential oil from C. obtusa on insects is not established. In this study, we tested the effects of essential oil extracted from C. obtusa on the physiologies and behaviors of Drosophila melanogaster and Musca domestica. Exposure to essential oil from C. obtusa decreased the lifespan, fecundity, locomotive activity, and developmental success rate of D. melanogaster. In addition, both fruit flies and house flies showed strong repellent behavioral responses to the essential oil, with duration times of about 5 hours at 70 μg/ml. These results suggest that essential oil from C. obtusa can be used as a ‘human-friendly’ alternative insect repellent.

Effects of carbon nanofiber on physiology of Drosophila

As nanomaterials are now widely utilized in a wide range of fields for both medical and industrial applications, concerns over their potential toxicity to human health and the environment have increased. To evaluate the toxicity of long-term exposure to carbon nanofibers (CNFs) in an in vivo system, we selected Drosophila melanogaster as a model organism. Oral administration of CNFs at a concentration of 1,000 μg/mL had adverse effects on fly physiology. Long-term administration of a high dose of CNFs (1,000 μg/mL) reduced larval viability based on the pupa:egg ratio, adult fly lifespan, reproductive activity, climbing activity, and survival rate in response to starvation stress. However, CNFs at a low concentration (100 μg/mL) did not show any significant deleterious effect on developmental rate or fecundity. Furthermore, long-term administration of a low dose of CNFs (100 μg/mL) increased lifespan and climbing ability, coincident with mild reactive oxygen species generation and stimulation of the antioxidant system. Taken together, our data suggest that a high dose of CNFs has obvious physiological toxicity, whereas low-dose chronic exposure to CNFs can actually have beneficial effects via stimulation of the antioxidant defense system.

Development of Resilience Index in Transport Systems

This paper demonstrates the quantification of the resilience index (RI) in transport systems. The transport infrastructure can be managed by using the concepts of resilience. Vugrin, Warren, Ehlen, & Camphouse (2010) emphasized the enhancement of resilience in infrastructure before disasters and the establishment of efficient measures for the recovery of systems in an emergency. The concept of resilience has a significant influence on transport planning and operations for disaster preparation. Lee, Kim, & Lee (2013) investigated the concepts of resilience and examined case studies using valuable asset-management techniques in order to maintain the resilience concepts which should be introduced in transport infrastructure planning and operations. Therefore, this paper presents the RI based on Vurgrin et al. (2010) and Lee et al. (2010). The first part of this paper focuses on the measurement of the RI using the recovery-dependent resilience (Vugrin et al., 2010) in transport infrastructures. For quantifying the RI, we have developed various variables that are used to target an achievable or a desired system performance in disaster recovery efforts. The second part of this paper focuses on the applications of the RI in case studies. The examined cases are road networks in flooded areas, heavy snowfall districts, and landslide occurrence zones. Each case is analyzed for transport costs both under normal and disaster conditions using the transport demand estimation models. Finally, we quantify the RI, which is important for establishing the provision of safety, recovery, and rehabilitation of transport infrastructures in flooding, snowfall, and landslide areas.

The effects of Korean mistletoe extract on endurance during exercise in mice

Many investigators have screened drugs and foods for the enhancement of endurance capacity and antifatigue. Mistletoe, a semiparasitic plant on various deciduous trees, has many known biological activities, including anticancer, anti-diabetes, antioxidant, and anti-cardiovascular disease effects. In a previous study, Korean mistletoe extract (KME) was reported to increase endurance capacity in mice. However, whether the administration of KME further enhances exercise performance, when combined with exercise training, was not investigated. In this study, we demonstrate that the administration of KME decreases the level of plasma lactate dehydrogenase, parameter of tissue damage and muscle fatigue when combined with exercise training. Exercise training increases the muscular glycogen and plasma free fatty acid (FFA) level, and KME administration in sedentary mouse group increases the plasma FFA level, indicating that KME administration alters the energy resources in muscle. In addition, KME administration enhances the exercise performance in sedentary mouse group, but did not further enhance exercise performance when combined with exercise training, suggesting that KME could be an excellent mimetic of exercise.

Transport Policy Directions Based on Travel Pattern Analysis in the Seoul Metropolitan Area

In the objective of this study is to analyze the travel patterns based on social changes between 1996 and 2002, and then to propose main directions in transport policies in the Seoul Metropolitan Area (SMA). This study examines the general travel pattern changes in the SMA and compares the travel patterns of regions invested in road construction (road-invested areas) with those of regions invested in transit (transit-invested areas). Study results show that while road investment had little effect on reducing congestion, the number of cars decreased in transit-invested areas due to the modal shift to transit modes. This study suggests that transit-oriented policies should be utilized as a solution to overcome severe traffic congestion.

CHAPTER 13:Lifespan-Extending Effect of Resveratrol and Other Phytochemicals

Phytochemicals are secondary metabolites synthesized by plants to provide assistance in survival and protection from environmental stress factors. Many phytochemicals have anti-oxidative and anti-inflammatory characteristics that improve health and prevent diseases, such as cancer, diabetes, cardiovascular disease, and neurodegenerative disorders, in animals. In addition to the health-improving and disease-preventing effects, phytochemicals also have been shown to retard the aging process and extend lifespans in various experimental animal studies using yeast, worms, flies, fishes, and rodents. In this chapter, we review the longevity benefits and putative underlying mechanisms of phytochemicals, including resveratrol, curcumin, quercetin, and catechin.

A Dynamic Shortest Path Algorithm Using Multi-Step Ahead Link Travel Time Prediction

Route guidance systems provide motorists with step-by-step instructions on how to get from any origin to any destination in a network. The systems calculate the best route from a user-supplied origin to destination, based on each link travel time on the network. Most studies on the route guidance development have been carried out based on only one-step ahead prediction of the link travel time in order to calculate a dynamic shortest path. However, the multi-step ahead prediction process should be considered in order to represent realistically the time-varying traffic conditions of the upstream links on the dynamic time interval basis. In this paper, a multi-step ahead prediction algorithm of link travel speeds has been developed using a Kalman filtering technique in order to calculate a dynamic shortest path. The one-step and the multi-step ahead link travel time prediction models for the calculation of the dynamic shortest path have been applied to the directed test network that is composed of 16 nodes: 3 entrance nodes, 2 exit nodes and 11 internal nodes. Time-varying traffic conditions such as flows and travel time data for the test network have been generated using the CORSIM model. The results show that the multi-step ahead algorithm is compared more favorably for searching the dynamic shortest time path than the other algorithm.

A Timetable-based Transit Assignment Model

In this paper, a transit assignment model has been developed on stochastic networks, with considering vehicle capacity and scheduled timetable. The stochastic network based transit assignment model is appropriate to apply for bus and metro networks altogether since it can distinguish between uncertain and reliable travel times characteristics by imposing stochastic parameters on links or lines. The vehicle capacity constraint based model is useful to evaluate some alternative operational plans and policies in transit networks. On the other hand, the scheduled timetable based model is necessary to evaluate detailed transit operations by calculating personal route choice based on the exact timetables of the transit operations. As a result of this we can assign the passengers in more realistic representation.