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Biomedical subjects

D Kim

Publications and source records attributed to D Kim.

At least 37 records · Page 2Linked to original sources
PubMed2001

Segmentation by evolution for visualization of the lower extremity of the Visible Man.

Medical image segmentation is the crucial process for three-dimensional (3D) modeling. Many studies have claimed to suggest more accurate ways of segmentation. However, such research seems to have the drawback that it works against the parsimony principle. These methods have to resegment the regions of interest (ROIs) for the already segmented data, without taking advantage of the vast amount of past segmentation results. The present report proposes a "segmentation by evolution" method. It is an advanced segmentation paradigm that incorporates the existing segmentation results. The "segmentation by evolution" paradigm was applied to the color images of the Visible Human data.

Anatomy, Cross-Sectional↗
PubMed2001

Synergetic analysis of spatio-temporal EEG patterns: Alzheimer's disease.

A spatio-temporal analysis has been employed on EEG signals recorded in groups of patients with Alzheimer's disease (AD). The so-called Karhunen-Loeve analysis method was applied to four groups of subjects: 12 patients who were diagnosed as having severe AD, 8 mild AD patients, 10 vascular dementia patients, and 10 normal aged controls, to obtain the spatio-temporal eigenpatterns. The local difference of the global EEG pattern in mild AD patients from that of normal controls was expanded to the frontal regions in the case of severe AD. The analysis showed significant bilateral temporal functioning differences and inter-hemispheric connection difficulty, along with remarkable intra-hemispheric correlation in severe AD patients. Compared to the normal controls, severe AD patients' brains exhibit only weak local connections and correlations, resulting into limited harmonious inter-hemispheric information processing. The results from the spatio-temporal EEG study of AD patients can be considered to be due to a change in the relative activity of the brain corresponding to the pathologic variation in AD, and the results are in accordance with reported clinical studies.

Alzheimer Disease↗
PubMed2001

Synergistic interaction and the role of C-terminus in the activation of TRAAK K+ channels by pressure, free fatty acids and alkali.

TRAAK is a member of the tandem-pore K+ channel family, and is expressed mainly in the brain. Using rat TRAAK (rTRAAK), we studied its single-channel kinetics, interactive modes of activation, and the role of the C-terminus on its pressure-, fatty-acid- and pH-sensitivity. When expressed in COS-7 cells, rTRAAK showed a mildly inwardly rectifying single-channel current/voltage relationship in symmetrical 140 mM KCl. Unlike TREK-1 and TREK-2, which are activated by acidic conditions, rTRAAK was activated by alkali conditions, such that a change in intracellular pH from 7.3 to 8.3 and 8.8 increased channel activity 5- and 14-fold, respectively. Pressure and alkali produced a strong synergistic activation, and pressure and arachidonic acid (AA) produced a mild synergistic activation. The only additive effect was observed with alkali and AA. Replacing the C-terminus of rTRAAK with that of TASK-1 or TASK-3 did not affect the response to pressure, AA or alkali. In contrast, replacing the C-terminus of TREK-2 with that of TASK-3 abolished the sensitivity to AA and acid, but not to pressure. These results show that rTRAAK is an alkali-sensing K+ channel that shows synergistic activation with pressure, and that the mechanism of activation of rTRAAK and TREK by free fatty acids are different.

Amino Acid Sequence↗
PubMed2001

The biological significance of phospholipase C beta 1 gene mutation in mouse sperm in the acrosome reaction, fertilization, and embryo development.

PURPOSE: We carried out this study to evaluate the biological significance of phospholipase C beta 1 gene mutation in mouse sperm in the acrosome reaction, fertilization, and embryo development. METHODS: Study subjects were divided into two groups according to the sperm [intact phospholipase C (PLC) beta 1 and PLC beta 1-/- C57BL/6J x CBA F1 mouse sperm] used. The positive acrosome reaction rate labeled with fluorescein isothiocyanate-Pisum sativum agglutinin, the fertilization rate, and the rate of embryos developed to the stage of morula or blastocyst in the two groups were compared. RESULTS: The mouse sperm null for the PLC beta 1 gene showed a lower acrosome reaction rate than control sperm (69.2 vs 50.9%, P < 0.05). And the fertilization rate and the rate of embryos developed to the stage of morula or blastocyst were also lower in the group using PLC beta 1-/- mouse sperm compared to the intact group (P < 0.05; 73.5 vs 51.8% and 15.7 vs 4.3%, respectively). CONCLUSIONS: Mutation of the PLC beta 1 gene in the mouse sperm reduces the acrosome reaction rate, fertilization rate, and embryo development rate, which may be the etiologic factors responsible for the low reproductive rate of PLC beta 1-/- mouse.

Acrosome Reaction↗
PubMed2001

PLC-beta1, activated via mGluRs, mediates activity-dependent differentiation in cerebral cortex.

During development of the cerebral cortex, the invasion of thalamic axons and subsequent differentiation of cortical neurons are tightly coordinated. Here we provide evidence that glutamate neurotransmission triggers a critical signaling mechanism involving the activation of phospholipase C-beta1 (PLC-beta1) by metabotropic glutamate receptors (mGluRs). Homozygous null mutation of either PLC-beta1 or mGluR5 dramatically disrupts the cytoarchitectural differentiation of 'barrels' in the mouse somatosensory cortex, despite segregation in the pattern of thalamic innervation. Furthermore, group 1 mGluR-stimulated phosphoinositide hydrolysis is dramatically reduced in PLC-beta1-/- mice during barrel development. Our data indicate that PLC-beta1 activation via mGluR5 is critical for the coordinated development of the neocortex, and that presynaptic and postsynaptic components of cortical differentiation can be genetically dissociated.

Animals↗
PubMed2001

Pigmentation in Koreans: study of the differences from caucasians in age, gender and seasonal variations.

BACKGROUND: Human skin colour shows variations throughout life, and many extrinsic and intrinsic factors influence melanogenesis. Facultative pigmentation of sun-exposed skin has been suggested to reflect cumulative lifetime ultraviolet (UV) exposure in caucasians. However, pigmentary changes due to various regulatory factors may be different in dark-skinned peoples. OBJECTIVES: To observe the variations in skin colour due to ageing, gender differences and seasonal changes in Koreans with skin type IV or V. METHODS: Skin pigmentation was measured at five body sites (buttock, glabella, the V of the neck area, inner arm and dorsal forearm) using skin reflectance spectroscopy in 497 subjects (age range 0-87 years) in winter and 311 subjects (age range 0-84 years) in summer. Among these subjects, 110 were assessed in both seasons. Three independent measurements at each site were done and the average value was used as the pigmentation level. RESULTS: Constitutive pigmentation of the buttock was highest in the first decade of life. It then decreased during the second decade and this decreased level was maintained after the third decade. In contrast to caucasians, facultative pigmentation and sun exposure index did not increase with ageing. Gender differences were significant at all body sites after the first decade. Seasonal changes were apparent in dorsal forearm pigmentation. Little difference was seen in forehead pigmentation between summer and winter. CONCLUSIONS: Basal melanogenic regulation might not be different between Asians and caucasians. However, the sun exposure index may not represent lifelong cumulative UV exposure in Koreans. Age-, gender- and season-related characteristics of skin pigmentation in Koreans imply that genetically determined basal skin colour plays an important part in characterizing later responsiveness to UV radiation and sex hormones. Understanding differences between races will be helpful in studying the regulatory mechanisms of melanogenesis.

Adolescent↗
PubMed2001

Arthroscopic suture tying: A comparison of knot types and suture materials.

PURPOSE: The purpose of this study was to determine the structural properties of 3 arthroscopically tied knots using 2 different suture materials: the French knot, the Duncan loop knot, and the original Revo knot. TYPE OF STUDY: Cohort analytic study. METHODS: The sutures used were No. 1 PDS II, an absorbent monofilament, and No. 1 Ethibond (Ethicon, Somerville, NJ), a braided nonabsorbent material. The resulting 6 suture-knot combinations were individually tested to failure in both open- and closed-loop configurations. RESULTS: The French knot showed the greatest strength compared with the Duncan loop and the Revo knot with both No. 1 Ethibond and No. 1 PDS II sutures (P <.05). The No. 1 Ethibond exhibited higher initial stiffness than the No. 1 PDS II for all 3 knot types (P <.05). Results were similar for both open and closed-loop configurations. Also, the French knot failed predominantly by suture breakage instead of knot slippage for both suture materials. CONCLUSIONS: The results of this study suggest that, among the suture and knot combinations investigated in this study, the arthroscopic repair of musculoskeletal injuries should be performed using the French knot and No. 1 Ethibond suture.

Arthroscopy↗
PubMed2001

A novel approach in treating recurrent bilateral hepaticojejunostomy biliary strictures post-liver transplantation: Successful use of Simpson's atherectomy device.

Biliary complications occur in 6% to 34% of patients who undergo orthotopic liver transplantation. Strictures at the anastomosis site or elsewhere in the biliary tract are common. These strictures are amenable to interventional radiological and surgical procedures; however, retransplantation is sometimes an inevitable outcome. An 8-year-old boy received combined liver and kidney transplants May 31, 1998. Hepatic artery thrombosis was diagnosed postoperative day 1 and treated with revascularization. The choledochojejunostomy was revised twice and resulted in a high hepaticojejunostomy. Significant strictures on both the right and left hepatic ducts at the anastomosis site were unsuccessfully treated by multiple interventional radiological procedures. The option of retransplantation was seriously explored. Simpson's atherectomy device was used in a novel approach February 24, 1999, and strictures on both ducts were successfully treated. At 1-year postprocedure, the patient has normal liver function with no evidence of recurrence of the strictures. Further experience with this novel technique is required to assess its role in treating biliary strictures post liver transplantation.

Atherectomy↗
PubMed2001

Akt/PKB promotes cancer cell invasion via increased motility and metalloproteinase production.

The Akt/protein kinase B (PKB) serine/threonine kinase is well known as an important mediator of many cell survival signaling pathways. Here, we demonstrate for the first time a major role of Akt/PKB in the cell invasion properties of the highly metastatic cell line HT1080. Using confocal microscopic analyses of live samples, we found Akt/PKB to be localized in the leading edge membrane area of migrating HT1080 cells. This localization was dependent on phosphoinositide 3-kinase and required the lipid binding ability of the phosphoinositide binding pleckstrin homology domain of Akt/PKB. We examined the possible function of Akt/PKB in HT1080 invasion. Surprisingly, Akt/PKB potently promoted HT1080 invasion, by increasing cell motility and matrix metalloproteinase-9 (MMP-9) production, in a manner highly dependent on its kinase activity and membrane-translocating ability. The increase in MMP-9 production was mediated by activation of nuclear factor-kappaB transcriptional activity by Akt/PKB. However, Akt/PKB did not affect the cell-cell or cell-matrix adhesion properties of HT1080. Our findings thus establish Akt/PKB as a major factor in the invasive abilities of cancer cells.

Cell Adhesion↗
PubMed2001

Microsurgical anatomy of the superior and recurrent laryngeal nerves.

OBJECTIVE: To study the microsurgical anatomy of the superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN) with respect to anatomic landmarks, and to identify their vascular supplies. METHODS: The microsurgical anatomy of the anterior neck, the course of the right and left SLN and RLN and their variations were studied in 21 cadavers. Fresh cadavers were perfused with colored silicon dye to investigate the microvasculature in detail. RESULTS: SLN originates from the inferior vagal ganglion at the C2 level and descends medially toward the thyrohyoid membrane. It branches into an external and an internal branch deep to the internal carotid artery at the C3 level. The external branch, along with the cricothyroid artery, descends deep to the superior thyroid artery toward the cricothyroid muscle. Accompanied by the superior laryngeal artery, the internal branch passes deep to the loop of the superior thyroid artery and pierces the thyrohyoid membrane. Both nerves reside in the fascia covering longus colli muscles and are supplied by their accompanying arteries. The loop of RLN is found at the T1-T3 level on the right, and more caudally at the T3-T6 level on the left, entering the larynx between C5-C7 levels on both sides. RLN receives arterial supply from the esophageal and tracheal branches of the inferior thyroid artery proximally, and by the inferior laryngeal artery distally. CONCLUSION: Incidental intraoperative injury to the SLN and RLN potentially could be avoided by understanding the detailed course of each nerve with respect to the surrounding anatomic landmarks and by recognizing their blood supplies.

Aged↗
PubMed2001

Interleukin-8 and intercellular adhesion molecule 1 regulation in oral epithelial cells by selected periodontal bacteria: multiple effects of Porphyromonas gingivalis via antagonistic mechanisms.

Interaction of bacteria with mucosal surfaces can modulate the production of proinflammatory cytokines and adhesion molecules produced by epithelial cells. Previously, we showed that expression of interleukin-8 (IL-8) and intercellular adhesion molecule 1 (ICAM-1) by gingival epithelial cells increases following interaction with several putative periodontal pathogens. In contrast, expression of IL-8 and ICAM-1 is reduced after Porphyromonas gingivalis ATCC 33277 challenge. In the present study, we investigated the mechanisms that govern the regulation of these two molecules in bacterially infected gingival epithelial cells. Experimental approaches included bacterial stimulation of gingival epithelial cells by either a brief challenge (1.5 to 2 h) or a continuous coculture throughout the incubation period. The kinetics of IL-8 and ICAM-1 expression following brief challenge were such that (i) secretion of IL-8 by gingival epithelial cells reached its peak 2 h following Fusobacterium nucleatum infection whereas it rapidly decreased within 2 h after P. gingivalis infection and remained decreased up to 30 h and (ii) IL-8 and ICAM-1 mRNA levels were up-regulated rapidly 2 to 4 h postinfection and then decreased to basal levels 8 to 20 h after infection with either Actinobacillus actinomycetemcomitans, F. nucleatum, or P. gingivalis. Attenuation of IL-8 secretion was facilitated by adherent P. gingivalis strains. The IL-8 secreted from epithelial cells after F. nucleatum stimulation could be down-regulated by subsequent infection with P. gingivalis or its culture supernatant. Although these results suggested that IL-8 attenuation at the protein level might be associated with P. gingivalis proteases, the Arg- and Lys-gingipain proteases did not appear to be solely responsible for IL-8 attenuation. In addition, while P. gingivalis up-regulated IL-8 mRNA expression, this effect was overridden when the bacteria were continuously cocultured with the epithelial cells. The IL-8 mRNA levels in epithelial cells following sequential challenge with P. gingivalis and F. nucleatum and vice versa were approximately identical and were lower than those following F. nucleatum challenge alone and higher than control levels or those following P. gingivalis challenge alone. Thus, together with the protease effect, P. gingivalis possesses a powerful strategy to ensure the down-regulation of IL-8 and ICAM-1.

Bacteroidaceae Infections↗
PubMed2001

Artificial ears for a biomimetic sonarhead: from multiple reflectors to surfaces.

This work presents an evolutionary approach to pinna design. Narrowband echolocating bats move the pinna to alter the directional sensitivity of their perceptual systems. Adding pinnae to RoBat--a biomimetic sonarhead mounted on a mobile robot--is the goal of this work. After a description of the earlier work on artificial pinnae consisting of multiple reflectors around the transducer, an acoustic model, inspired by a physical model of sound diffraction and reflections in the human concha, is described and revisited as the model to use for evolving complex shapes. A genetic algorithm evolved the shape of the pinnae with respect to desired features of the directivity pattern of the receiver transducers. Some interesting paraboloid shapes for specific echolocating behaviors were evolved, improving performance with respect to the bare transducer's performance.

Animals↗
PubMed2001

Motivating factors in futile clinical interventions.

With modern medical technology, it is now possible to sustain life for prolonged periods in critically ill patients, even when there is no reasonable hope of improvement or achieving the goals of therapy. Such futile and medically inappropriate interventions may violate both the ethical and medical precepts generally accepted by patients, families, and physicians. In this study, we sought to determine who was primarily responsible for such interventions, the nature of their motivation, and the role of a timely bioethical consultation. In a retrospective review, we identified 100 patients of 331 bioethical consultations who had futile or medically inappropriate therapy. The average age of patients was 73.5 +/- 32 years (mean +/- 2 SD) with 57% being male. Fifty-seven percent of the patients were admitted to the hospital with a degenerative disorder, 21% with an inflammatory disorder, and 16% with a neoplastic disorder. The family was responsible for futile treatment in 62% of cases, the physician in 37% of cases, and a conservator in one case. Unreasonable expectation for improvement was the most common underlying factor. Family dissent was involved in 7 of 62 cases motivated by family, but never when physicians were primarily responsible. Liability issues motivated physicians in 12 of 37 cases where they were responsible but in only 1 of 62 cases when the family was (chi(2) 5 degrees of freedom = 26.7, p < 0.001). When the bioethics consultation resulted in cessation of the therapy, patients died in a median of 2 days as opposed to 16 days if therapy continued (p < 0.001).

Aged↗
PubMed2001

Schizophrenic delusions in Seoul, Shanghai and Taipei: a transcultural study.

In this transcultural study of schizophrenic delusions among patients in Seoul, Shanghai and Taipei, we discovered that both the frequency and content of delusions differed among the three groups; and that these differences could perhaps be explained by varying sociocultural and political situations. Delusional themes that are sensitive to sociocultural or political situations include guilt, love/sex, religion, somatic damage, economy/business and politics. Delusions regarding longevity, love/sex, dysmorphophobia/dysosmophobia, religion or supernatural matters, and espionage/spy stories were most frequent in Seoul patients. Those in Taipei predominantly had delusions about possession, religion or supernatural matters, hypnotism, and mass media/computers. Shanghai patients often had delusions of poisons, being prickled by poisoned needles, their brain and viscera extracted and being a family member of political authorities.

Adult↗
PubMed2001

Interleukin-10 attenuates proinflammatory cytokine production and improves survival in lethal pancreatitis.

Given that interleukin (IL)-10 (IL-10) serves as a potent down-regulator of specific proinflammatory cytokines we reasoned that its administration should improve outcome in situations in which the biological response to a severe inflammatory challenge is the critical determinant of survival. To test our hypothesis we administered IL-10 in the setting of lethal pancreatitis to determine its effect on proinflammatory cytokine production and survival. We divided Sprague-Dawley rats into three groups. Controls (Group 1, n = 5) received a sham laparotomy. We induced pancreatitis in Group 2 (n = 9) and Group 3 (n = 9) via laparotomy and intrapancreatic infiltration of one mL of 5 per cent sodium taurocholate. Group 2 was treated only with saline, whereas Group 3 was treated with 10,000 units of IL-10 (in saline) at 30 minutes, 3.5 hours, and 6.5 hours after induction of pancreatitis. Serial blood samples were obtained at 6.5 hours for measurement of amylase, IL-1, and IL-6. The Kaplan-Meier method, Wilcoxon test, and Student's t test were used for analysis. Seven-day survival was 100, 0, and 45 per cent in Groups 1, 2, and 3, respectively. Production of amylase, IL-1, and IL-6 was lower in the IL-10-treated group (Group 3) compared with the group treated with saline alone (Group 2, P < 0.05). We conclude that administration of IL-10 in the setting of otherwise 100 per cent lethal experimental pancreatitis significantly reduces production of amylase, IL-1, and IL-6 and improves survival.

Amylases↗
PubMed2001

Clinical fluoroscopic fiducial-based registration of the vertebral body in spinal neuronavigation.

We present a system involving a computer-instrumented fluoroscope for the purpose of 3D navigation and guidance using pre-operative diagnostic scans as a reference. The goal of the project is to devise a computer-assisted tool that will improve the accuracy, reduce risk, minimize the invasiveness, and shorten the time it takes to perform a variety of neurosurgical and orthopedic procedures of the spine. For this purpose we propose an apparatus that will track surgical tools and localize them with respect to the patient's 3D anatomy and pre-operative 3D diagnostic scans using intraoperative fluoroscopy for in situ registration and embedded fiducials. Preliminary studies have found a fiducial registration error (FRE) of 1.41 mm and a Target Localization Error (TLE) of 0.48 mm. The resulting system leverages equipment already commonly available in the operating room (OR), providing an important new functionality that is free of many current limitations, while keeping costs contained.

Artificial Intelligence↗
PubMed2000

Mechanism of superoxide anion generation in the toxic red tide phytoplankton Chattonella marina: possible involvement of NAD(P)H oxidase.

Red tide phytoplankton Chattonella marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O(2)(-)), hydrogen peroxide (H(2)O(2)) and hydroxyl radical (&z.rad;OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. marina, the mechanism of ROS generation in C. marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. marina cells showed NAD(P)H-dependent O(2)(-) generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O(2)(-) production in C. marina.

Amino Acid Sequence↗