• Corrosion Science and Technology
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• 제7권3호
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• pp.162-167
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• 2008

Degradable implants have been in use for bone surgery for decades. However, degradable metal implants are one of the new research areas of biomaterials science. Magnesium has good biocompatibility due to its low toxicity, and it is a corroding, i.e. dissolvable, metal. Furthermore, magnesium is needed in human body, and naturally found in bone tissue. There have been some published reports also asserting the potential bone cell activation or bone healing effect of high magnesium ion concentrations. The classic method for achieving intertransverse process fusion involves autogenous iliac crest bone graft. Several investigations have been performed to enhance this type of autograft fusion. However, there is no research which has been undertaken to investigate the efficiency of pure magnesium particles in posterolateral spinal fusion. In this study, corrosion behavior of magnesium metal at the bone interface, the possibility of new bone cell formation and the degree of effectiveness in producing intertransverse process lumbar fusion in a sheep model have been investigated. Cortical bone screws were machined from magnesium alloy AZ31 extruded rod and implanted to hip-bones of sheep via surgery. Three months after surgery, the bone segments carrying these screws were removed from the sacrificed animals. Samples were sectioned to reveal Mg/bone interfaces and investigated using optical microscope, SEM-EDS and radiography. Optical and SEM images showed that there was a significant amount of corrosion on the magnesium screw. The elemental mapping results indicate, due to the presence of calcium and phosphorus elements, that there exists new bone formation at the interface. Furthermore, sixteen sheep were subjected to intertransverse process spinal fusions with pedicle screw fixation at various locations along their spines. Each animal was treated with 5cc autograft bone at one fusion level and 1cc magnesium+5cc autograft bone at the other. Six months after surgery, bone formation was evaluated by gross inspection and palpation, and radiological, histological, scanning electron microscopic and x-ray diffraction analyses. It may be stated that the potential for using useful corrosion of magnesium alloys in medical applications is expected to be significant.

• Investigative Magnetic Resonance Imaging
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• 제2권1호
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• pp.50-57
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• 1998

경사 자계 펄스에 의한 MR 소음은 환자의 촬영뿐만 아니라 뇌기능 영상과 같은 신경 과학 영상에도 문제점 중의 하나이다. 특히 뇌기능 영상에서 소음은 피질과 혈관의 산소량의 변화로부터 생기는 작은 신호의 변화에 영향을 미치는 심각한 잡음 중의 하나이다. 본 연구에서는 청각, 운동, 및 시각피질에서 소음이 뇌기능 영상에 미치는 영향을 알아보고자 하였다. 그 결과 소음이 운동과 시각 피질에 미치는 여향은 서로 반대였다. 즉, 운동 피질에서는 소음이 총반응을 증가시켰고, 반대로 시각 피질에서는 소음이 총반응을 감소시켰다. 현재의 연구가 시작 단계에 있고, 앞으로 더 많은 실험적 검증이 필요한 실정이나, 소음이 운동과 시각 피질의 뇌기능 영상에 미치는 여향에 관한 첫번째 보고이며, 이결과는 앞으로 뇌기능 연구의 데이터 해석에 기초 자료로 이용될 수 있다.

• Molecules and Cells
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• 제40권8호
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• pp.558-566
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• 2017

Regular monitoring on experimental animal management found the fluctuation of ART outcome, which showed a necessity to explore whether superovulation treatment is responsible for such unexpected outcome. This study was subsequently conducted to examine whether superovulation treatment can preserve ultrastructural integrity and developmental competence of oocytes following oocyte activation and embryo culture. A randomized study using mouse model was designed and in vitro development (experiment 1), ultrastructural morphology (experiment 2) and functional integrity of the oocytes (experiment 3) retrieved after PMSG/hCG injection (superovulation group) or not (natural ovulation; control group) were evaluated. In experiment 1, more oocytes were retrieved following superovulation than following natural ovulation, but natural ovulation yielded higher (p < 0.0563) maturation rate than superovulation. The capacity of mature oocytes to form pronucleus and to develop into blastocysts in vitro was similar. In experiment 2, a notable (p < 0.0186) increase in mitochondrial deformity, characterized by the formation of vacuolated mitochondria, was detected in the superovulation group. Multivesicular body formation was also increased, whereas early endosome formation was significantly decreased. No obvious changes in other microorganelles, however, were detected, which included the formation and distribution of mitochondria, cortical granules, microvilli, and smooth and rough endoplasmic reticulum. In experiment 3, significant decreases in mitochondrial activity, ATP production and dextran uptake were detected in the superovulation group. In conclusion, superovulation treatment may change both maturational status and functional and ultrastuctural integrity of oocytes. Superovulation effect on preimplantation development can be discussed.

• The Korean Journal of Physiology and Pharmacology
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• 제23권2호
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• pp.121-130
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• 2019

Glutamate toxicity-mediated mitochondrial dysfunction and neuronal cell death are involved in the pathogenesis of several neurodegenerative diseases as well as acute brain ischemia/stroke. In this study, we investigated the neuroprotective mechanism of dieckol (DEK), one of the phlorotannins isolated from the marine brown alga Ecklonia cava, against glutamate toxicity. Primary cortical neurons ($100{\mu}M$, 24 h) and HT22 neurons (5 mM, 12 h) were stimulated with glutamate to induce glutamate toxic condition. The results demonstrated that DEK treatment significantly increased cell viability in a dose-dependent manner ($1-50{\mu}M$) and recovered morphological deterioration in glutamate-stimulated neurons. In addition, DEK strongly attenuated intracellular reactive oxygen species (ROS) levels, mitochondrial overload of $Ca^{2+}$ and ROS, mitochondrial membrane potential (${\Delta}{\Psi}_m$) disruption, adenine triphosphate depletion. DEK showed free radical scavenging activity in the cell-free system. Furthermore, DEK enhanced protein expression of heme oxygenase-1 (HO-1), an important anti-oxidant enzyme, via the nuclear translocation of nuclear factor-like 2 (Nrf2). Taken together, we conclude that DEK exerts neuroprotective activities against glutamate toxicity through its direct free radical scavenging property and the Nrf-2/HO-1 pathway activation.

• 대한통합의학회지
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• 제7권3호
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• pp.171-180
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• 2019

Purpose : The purpose of this study was to investigate the difference in motor cortical excitability during mental practice and action observation in subjects with forward head posture. Methods : This study was performed in two groups, a forward head posture group (n=17) and a normal posture group (n=17). Electroencephalography (EEG) was conducted to investigate cerebral cortex activity, and six electrodes were attached to Fp1, Fp2, C1, C2, C3, and C4 to measure the relative alpha power, relative beta power, relative gamma power, and mu rhythms. The subjects were requested to perform the four different conditions, which were eye opening, eye closing, mental practice, and action observation for 300 seconds. Results : The results showed that the relative alpha waves showed a significant difference between the normal and forward head posture groups in the C1, C2, C3, and C4 regions with the eyes open (p<.05). The relative beta waves also showed a significant difference between the two groups in the Fp1 and Fp2 regions during action observation (p<.05). The relative gamma waves were significantly different between the normal and forward head posture groups in the Fp1 and Fp2 regions during action observation (p<.05) in C1, C2, and C3 with eyes closed (p<.05) and in C1, C2, C3, and C4 with eyes open (p<.05). Conclusion : The results of this study showed that EEG change in the forward head posture group was different from that in the normal control group in action observation rather than in mental practice. Therefore, we are expected to provide a neurophysiological basis for applying action observation to motor skill learning during exercise for correcting forward head posture.

• Journal of Periodontal and Implant Science
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• 제30권2호
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• pp.359-374
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• 2000

Cyclosporine A(CsA) is a widely used immunosuppressant for transplant patients and is also used for the treatment of a wide variety of systemic diseases with immunologic disorders. However, its use is frequently limited because of complications such as nephrotoxicity or gingival hyperplasia. Although several hypotheses have been postulated for CsA-induced gingival hyperplasia, i.e. various cytokine effects of inflammatory cells, existence of plaque or CsA itself, but its pathogenesis is still unclear. For experimental chronic CsA toxicity, salt depletion has been shown to increased susceptibility of rodents to the effects of CsA, and this maneuver facilitates production of arteriolopathy and interstitial fibrosis in kidney that mimic the changes found in human. The purpose of this study was to evaluate pathogenesis of CsA-induced gingival hyperplasia by comparing changes between CsA administration groups of normal standard diet and those of low salt diet group. Specific pathogen-free, 20 to 25 days old(120 to 150 g), male Fisher-344 rats(KIST, Korea), 120 to 150g of body weight, were assigned to four groups of six animals each after one week of adaptation period for powder food. Group 1 received olive oil($300{\mu}l/g\;of\;diet$) with normal standard diet(0.4% of sodium)(NSD). Group 2 received CsA(Cypol-N, Jonggundang, Korea; $300{\mu}g/g\;of\;diet$) with normal standard diet(NSD+CsA). Group 3 received same amount of olive oil with low salt diet(0.05 % of sodium, Teklad Premier, U.S.A.)(LSD). Group 4 received same dose of CsA with low salt diet(LSD+CsA). Rats were pair fed and were sacrificed after six weeks. Renal histologic lesions associated with CsA, consisted of cortical interstitial fibrosis, tubular atrophy and hyalinization of arterioles and the impairment of renal function including increase of serum creatinine and decrease of glomerular filtration rate was more severe in low salt diet group. These were proved as the results of activated of renin-angiotensin system in the kidney by low salt condition. Meanwhile the degree of gingival hyperplasia at incisor and molar tooth was less severe in low salt diet group compared with normal sodium diet group. Hyperplastic gingiva showed mild epithelial hyperplasia and expanded underlyng stroma which consisted of matrix increasement, capillary proliferation and dilatation. While the number and the activation of fibroblasts were increased, inflammatory cells were rare in the stroma. The immunohistochemistry for TGF-${\beta}_1$ in the kidney and gingiva revealed stronger positive in LSD+CsA in kidney but in gingiva of NSD+CsA. These results suggested followings; Gingival hyperplasia can be developed without inflammatory cells infiltration and seemed not induced by CsA by itself. The major role for gingival hyperplasia by CsA would be the secondary effect of TGF-${\beta}$, which maybe upregulated by CsA administration. Low salt diet can attenuate this hyperplasia perhaps by decreasing the activation of $TGF-{\beta}$.

• Corrosion Science and Technology
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• 제8권4호
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• pp.162-169
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• 2009

Pure titanium and its alloys are drastically used in implant materials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus than cortical bone. Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. For this reason, Ti-30Ta-xZr alloy systems have been studied in this study. The Ti-30Ta containing Zr(5, 10 and 15 wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24 hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and Ti coating and then coated with TiN, respectively, by using DC magnetron sputtering method. The analyses of coated surface were carried out by field emission scanning electron microscope(FE-SEM). The electrochemical characteristics were examined using potentiodynamic (- 1500 mV~+ 2000 mV) and AC impedance spectroscopy(100 kHz~10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The equiaxed structure was changed to needle-like structure with increasing Zr content. The surface defects and structures were covered with TiN/Ti coated layer. From the polarization behavior in 0.9% NaCl solution, The corrosion current density of Ti-30Ta-xZr alloys decreased as Zr content increased, whereas, the corrosion potential of Ti-30Ta-xZr alloys increased as Zr content increased. The corrosion resistance of TiN/Ti-coated Ti-30Ta-xZr alloys were higher than that of the TiN-coated Ti-30Ta-xZr alloys. From the AC impedance in 0.9% NaCl solution, polarization resistance($R_p$) value of TiN/Ti coated Ti-30Ta-xZr alloys showed higher than that of TiN-coated Ti-30Ta-xZr alloys.

• 생명과학회지
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• 제33권6호
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• pp.455-462
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• 2023

임신 중 감염에 의한 산모의 면역 활성화는 조현병과 자폐 스펙트럼 장애를 포함한 신경 발달 질환의 위험을 증가시킨다. 여러 연구에서 poly (I:C) 또는 LPS를 사용하여 모체 면역 활성화 유도한 자손에서 비정상적인 행동과 뇌 발달을 관찰하였다. 또한 최근 뇌에 상주하며 면역 세포로 기능하는 미세아교세포가 MIA 유발 자손의 행동 이상과 뇌 발달에 중요한 역할을 한다는 것이 보고되고 있으나 아직 메커니즘은 명확하지 않다. 본 연구에서는 GPCR의 구성원인 GPR56의 미세아교세포 특이적 억제가 행동 이상과 뇌 발달을 유발하는지 여부를 조사하였다. 먼저, MIA 유도는 발달 중인 뇌의 미세아교세포 집단에 영향을 미치지 않으나, 미세아교세포를 분리하여 GRP56의 발현을 조사한 결과, MIA 유도 태아에서 성별에 관계 없이 E14.5와 E18.5 사이에서 GPR56 발현이 억제됨을 관찰하였다. 그리고 미세아교세포 특이적 GPR56 억제는 MIA 유도 자손에게서 나타나는 사교성 결손, 반복적인 행동 패턴 및 증가된 불안 수준과 같은 비정상적인 행동을 관찰하였다. 미세아교세포 GPR56 억제 마우스에서는 MIA 유도 자손과 같은 비정상적인 피질 발달이 관찰되지 않았지만, c-fos 염색을 통해 뇌 활동이 관찰되었다. 따라서 본 연구는 미세아교세포 특이적 GPR56 결핍이 이상 행동을 유발함을 시사하며, 추후 연구를 통해 MIA 자손의 행동 결손 진단 및/ 치료 표적을 위한 바이오마커로 활용될 수 있음을 시사한다.

• 수면정신생리
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• 제20권2호
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• pp.75-81
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• 2013

목 적 : 혐오 자극에 대한 뇌의 기능적 영상 연구에 있어서 기능적 자기공명영상, 양전자방출단층촬영 등의 연구는 많이 진행되어 있으나 저해상 전자기 단층촬영(low resolution brain electromagnetic tomography) 분석을 이용한 연구는 거의 없다. 본 연구의 목적은 피험자들에게 시각적 혐오자극을 준 후 나타나는 대뇌 피질의 활성변화를 저해상 전자기 단층촬영을 이용하여 파악하고자 하는 것이다. 방 법 : 총 45명($27.1{\pm}2.6$세)의 건강한 젊은 성인남녀가 연구에 참여하였다. 국제정서사진체계를 사용하여 중립자극에서 4장, 신체훼손과 관련된 혐오자극에서 4장의 사진을 뽑아 피험자들에게 각 30초간 보여주면서 뇌파를 측정하였다. 저해상 전자기 단층촬영분석을 시행하여 중립자극에 대비해 혐오자극에서의 변화된 전류밀도를 비교 분석하였다. 결 과 : 혐오시각 자극을 받는 동안 피험자 모두 불쾌감, 놀람, 스트레스를 받았다고 보고하였다. 저해상 전자기 단층촬영 분석상 세타파에서 좌측 전두엽의 위이마이랑(BA10)과 중간이마이랑(BA10, 11) 영역에서 유의미한 전류밀도의 감소를 보이는 복셀 클러스터가 관찰되었다. 이 복셀 클러스터는 총 11개의 복셀로 구성되어 있으며 유의미한 전류밀도(p<0.05)의 감소를 나타내는 t값의 임계값은 -1.984이었다. 남녀 간의 혐오 반응 정도에 유의미한 차이는 없었다. 결 론 : 이 연구의 결과인 시각 혐오자극에 의한 배외측 전전두엽의 활성은 혐오 정서의 조절과 관여되어 있을 것으로 생각된다.

• 치과방사선
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• 제23권2호
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• pp.229-250
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• 1993

This study was performed to investigate the morphological and structural changes of bone tissues and the effects of irradiation on the mandibular bodies of rats which were fed low calcium diets. In order to carry out this experiment, 160 seven-week old Sprague-Dawley strain rats weighing about 150 gm were selected and equally divided into one normal diet group of 80 rats and one low calcium diet group with the remainder. These groups were then subdivided into two groups, 40 were assigned rats for each subdivided group, exposed to radiation. The Group 1 was composed of forty non-irradiated rats with normal diet, Group 2 of forty irradiated rats with normal diet, Group 3 forty non-irradiated rats with low calcium diet, and Group 4 forty irradiated rats with low calcium diet. The two irradiation groups received a single dose of 20 Gy on the jaw area only and irradiated with a cobalt-50 teletherapy unit. The rats with normal and low calcium diet groups were serially terminated by ten on the 3rd, the 7th, the 14th, and the 21st day after irradiation. After termination, both sides of the dead rats mandible were removed and fixed with 10% neutral formalin. The bone density of mandibular body was measured by use of bone mineral densitometer(Model DPX -alpha, Lunar Corp., U.SA). Triga Mark ill nuclear reactor in Korea Atomic Research Institute was used for neutron activation and then calcium contents of mandibular body were measured by using a 4096 multichannel analyzer (EG and G ORTEC 919 MCA, U.SA). Also the mandibular body was radiographed with a soft X-ray apparatus(Hitex Co., Ltd., Japan). Thereafter, the obtained microradiograms were observed by a light microscope and were used for the morphometric analysis using a image analyzer(Leco 2001 System, Leco Co., Canada). The morphometric analysis was performed for parameters such as the total area, the bone area, the inner and outer perimeters of the bone. The obtained results were as follows: 1. In the morphometric analysis, total area and outer perimeter of the mandibular bodies of Group 3 were a little smaller than that of Group 1. The mean bone width and bone area were much smaller than that of Group 1 and the inner perimeter of Group 3 was much longer than that of Group 1. The total area and outer perimeter of Group 2 and Group 4 showed little difference. The mean bone width and bone area of Group 4 were smaller than that of Group 2 and the inner perimeter of Group 4 was longer than that of Group 2. 2. The remarkable decreases of the number and thickness of trabeculae and also the resorption of endosteal surface of cortical bone could be seen in the microradiogram of Group 3, Group 4 since the 3rd day of experiment. On the 21st day of experiment, the above findings could be more clearly seen in Group 4 than in Group 3. 3. The bone mineral density of Group 3 was lesser than that of Group 1 and the bone mineral density of Group 4 was lesser than that of Group 2 on the 7th, 14th, 21st days. The irradiation caused the bone mineral density to be decreased regardless of diet. In the case of Groups with low calcium diet, the bone mineral density was much decreased on the 21st day than on the 3rd day of experiment. 4. The calcium content in mandible of Group 3 was smaller than that of Group 1 throughout the experiment. roup 4 showed the least amount of calcium content. The irradiation caused the calcium content to be decreased regardless of diet. In the case of Groups with low calcium diet, the calcium content was much decreased on the 21st day than on the 3rd day of experiment. In conclusion, the present study demonstrated that morphological changs and decrease of bone mass due to resorption of bone by low calcium diet, and that the resorption of bone could be found in the spongeous bone and endosteal surface of cortical bone. So the problem of resorption of bone must be considered when the old and the postmenopausal women are taken radiotherapy because the irradiation seems to be accelerated the resorption of osteoporotic bone.