• Environmental Analysis Health and Toxicology
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• v.23 no.2
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• pp.67-77
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• 2008

It has been observed that the linear relationship between the logarithm of bioconcentration factor (log BCF) of highly hydrophobic chemicals and their log $K_{ow}$ breaks when log $K_{ow}$ becomes greater than 6.0. Consequently, super hydrophobic chemicals were not thought to cause baseline toxicity as a single compound. Researchers often call this phenomenon as "hydrophobicity cutoff" meaning that bioconcentration or corresponding baseline toxicity has a certain cutoff at high log $K_{ow}$ value of hydrophobic organic pollutants. The underlying assumption is that the increased molecular size with increasing hydrophobicity prohibits highly hydrophobic compounds from crossing biological membranes. However, there are debates among scientists about mechanisms and at which log $K_{ow}$ this phenomenon occurs. This paper reviews three hypotheses to explain observed "cutoff": steric effects, kinetic or physiological limitations, and chemical activity cutoff. Although the critical molecular size that makes biological membranes not permeable to hydrophobic organic chemicals is uncertain, size effects in combination with kinetic limitation would explain observed non-linearity between log BCF and log $K_{ow}$. Chemical activity of hydrophobic chemicals generally decreases with increasing melting point at their aqueous solubility. Thus, there may be a chemical activity cutoff of baseline toxicity if there is a critical chemical activity over which baseline effects can be observed.

• BMB Reports
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• v.57 no.8
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• pp.352-362
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• 2024

Hematopoietic stem cell transplantation (HSCT) remains an indispensable therapeutic strategy for various hematological diseases. This review discusses the pivotal role of bone marrow (BM) niches in influencing the efficacy of HSCT and evaluates the current animal models, emphasizing their limitations and the need for alternative models. Traditional animal models, mainly murine xenograft, have provided significant insights, but due to species-specific differences, are often constrained from accurately mimicking human physiological responses. These limitations highlight the importance of developing alternative models that can more realistically replicate human hematopoiesis. Emerging models that include BM organoids and BM-on-a-chip microfluidic systems promise enhanced understanding of HSCT dynamics. These models aim to provide more accurate simulations of the human BM microenvironment, potentially leading to improved preclinical assessments and therapeutic outcomes. This review highlights the complexities of the BM niche, discusses the limitations of current models, and suggests directions for future research using advanced model systems.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2003.11a
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• pp.74-77
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• 2003

A new health paradigm may be evolving that would place emphasis on the positive aspects of diet, identifying components that are physiologically active and that contribute to the prevention of disease onset. It has been increasingly difficult to evaluate the impact of new bioactive materials and food products on the well being of society. Thus, testing systems for both health function and toxicity have become very elaborate, complex, and interrelated, making their interpretation difficult and open to controversy. To select the proper starting materials, to screen the appropriate health functionality and to determine the efficacy of product, a reliable, reproducible, sensitive and predictive assay is required. Particularly, in uitro assay is the first stage in preclinical test on physiologically active materials and have many advantages in terms of time, cost and convenience. However, several factors as well as some limitations should be considered in this assay system. This presentation, therefore, will address the use of in uitro assays for evaluating physiological functionality of foods coupled with general consideration.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.95-98
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• 1997

In this paper, several nonlinear system identification theories and the application of these methods to the physiological system are reviewed by extracting significant results from the literature. Methods based on unctional series expansion, parameter estimation, block-oriented models are included. However, there is still considerable debate about the advantages and disadvantages of each approach. This is true primarily because each method has limitations on the types of assumption and interpretation, types of nonlinear elements, etc. This means that user must select an appropriate method and the selection will depend on the problem under investigation.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.6
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• pp.513-519
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• 2013

The current vision-based approaches for emotion recognition, such as facial expression analysis, have many technical limitations in real circumstances, and are not suitable for applications that use them solely in practical environments. In this paper, we propose an approach for emotion recognition by combining extrinsic representations and intrinsic activities among the natural responses of humans which are given specific imuli for inducing emotional states. The intrinsic activities can be used to compensate the uncertainty of extrinsic representations of emotional states. This combination is done by using PRMs (Probabilistic Relational Models) which are extent version of bayesian networks and are learned by greedy-search algorithms and expectation-maximization algorithms. Previous research of facial expression-related extrinsic emotion features and physiological signal-based intrinsic emotion features are combined into the attributes of the PRMs in the emotion recognition domain. The maximum likelihood estimation with the given dependency structure and estimated parameter set is used to classify the label of the target emotional states.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.91-98
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• 1990

This paper reviews the previous researches related to the effects of whole-body vibration on human performance. The physiological effects of vibration were reviewed in the first part, and the effects of vibration on vision and manual control performance were discussed. the relationships between vibration and ride quality were also discussed. ISO-2631 was briefly reviewed, and cautions and limitations were discussed to avoid misinterpretations when we accomodate Korean population to this standard. Further researches were recommended to get better understanding of response characteristics of Korean to whole-body vibration.

• BMB Reports
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• v.45 no.11
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• pp.612-622
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• 2012

Olfactory receptors (ORs) detect volatile chemicals that lead to the initial perception of smell in the brain. The olfactory receptor (OR) is the first protein that recognizes odorants in the olfactory signal pathway and it is present in over 1,000 genes in mice. It is also the largest member of the G protein-coupled receptors (GPCRs). Most ORs are extensively expressed in the nasal olfactory epithelium where they perform the appropriate physiological functions that fit their location. However, recent whole-genome sequencing shows that ORs have been found outside of the olfactory system, suggesting that ORs may play an important role in the ectopic expression of non-chemosensory tissues. The ectopic expressions of ORs and their physiological functions have attracted more attention recently since MOR23 and testicular hOR17-4 have been found to be involved in skeletal muscle development, regeneration, and human sperm chemotaxis, respectively. When identifying additional expression profiles and functions of ORs in non-olfactory tissues, there are limitations posed by the small number of antibodies available for similar OR genes. This review presents the results of a research series that identifies ectopic expressions and functions of ORs in non-chemosensory tissues to provide insight into future research directions.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.6
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• pp.370-375
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• 2016

Recent advances in systems biology are shedding a new light on the traditional medicine research. The systems biology highlights the way each component interacts with each other within a system, and the network behavior that emerges from such interactions. This feature of systems biology can accent the systemic aspects of Korean medicine such as the mechanism of action of herbal formulae, pattern differentiation, and the meridian systems, as both the Korean medicine and the systems biology theorize the human physiological functions and phenomena from a holistic point of view. This paper outlines the meaning of the recent Korean medicine research using the systems biology methodology. We discuss the methodologies of the two fields in a comparative manner, and overview the advantages and limitations of the integrated approaches. Finally, we suggest the future prospects for the systems biology inspired approaches to the Korean medicine research. The systems biology may provide a new modernized research methodology for the Korean medicine that can highlight its unique features.

• International Journal of Stem Cells
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• v.17 no.1
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• pp.30-37
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• 2024

The lung is a complex organ comprising a branched airway that connects the large airway and millions of terminal gas-exchange units. Traditional pulmonary biomedical research by using cell line model system have limitations such as lack of cellular heterogeneity, animal models also have limitations including ethical concern, race-to-race variations, and physiological differences found in vivo. Organoids and on-a-chip models offer viable solutions for these issues. Organoids are three-dimensional, self-organized construct composed of numerous cells derived from stem cells cultured with growth factors required for the maintenance of stem cells. On-a-chip models are biomimetic microsystems which are able to customize to use microfluidic systems to simulate blood flow in blood channels or vacuum to simulate human breathing. This review summarizes the key components and previous biomedical studies conducted on lung organoids and lung-on-a-chip models, and introduces potential future applications. Considering the importance and benefits of these model systems, we believe that the system will offer better platform to biomedical researchers on pulmonary diseases, such as emerging viral infection, progressive fibrotic pulmonary diseases, or primary or metastatic lung cancer.

• The Korean Journal of Nuclear Medicine
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• v.36 no.1
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• pp.80-86
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• 2002

Presently, PET is widely used in oncology, but suffers from limitations of poor anatomical information. To compensate for this weakness, a combined PET/CT has been developed by Professor Townsend at the University of Pittsburgh Medical Center. The prototype was designed as PET and CT components combined serially in a gantry. The CT images provide not only accurate anatomical location of the lesions but also transmission map for attenuation correction. More than 300 cancer patients have been studied with the prototype of PET/CT since July, 1998. The PET/CT studies affected the managements in about $20{\sim}30%$ of cancer patients. These changes are a consequence of the more accurate localization of functional abnormalities, and the distinction of pathological from normal physiological uptake. Now a variety of combined PET/CT scanners with high-end PET and high-end CT components are commercially available. With the high speed of multi-slice helical CT, throughput of patient's increases compared to conventional PET. Although some problems (such as a discrepancy in breathing state between the two modalities) still remain, the role of PET/CT in oncology is very promising.