Biomedical subjects

S Kwon

Publications and source records attributed to S Kwon.

At least 19 recordsLinked to original sources

PubMed2006

[Hans-Christian Jacobaeus (1879-1937): The inventor of human laparoscopy and thoracoscopy].

Already 94 years ago in 1910, Dr. Hans Christian Jacobaeus performed the first clinical laparoscopic surgery in Stockholm. His pioneering procedure was based on the animal experiments of Georg Kelling (1866-1945), a German physician from Dresden, who performed the first laparoscopic intervention in 1901 using a Nitze cystoscope in a dog. In 1910 Jacobaeus published his first experiences with laparoscopic surgery in the Münchner Medizinische Wochenschrift under the title "The possibility to perform cystoscopy in examinations of serous cavities." He used this technique for diagnostic purposes in unclear abdominal complaints and functional impairment. Jacobaeus was the first who pointed out the possibility of causing injury to organs, especially the gut, by inserting the trocar. In 1910 Jacobaeus recognized the immense diagnostic and therapeutic possibilities of laparoscopic surgery, but also the difficulties and limits. He also was the first who recognized the need to complete training sessions on animals and corpses. He demanded the development of special laparoscopic instruments to optimize and simplify the operation.

Animals↗

PubMed2006

New process control strategy for wastewater chlorination and dechlorination using ORP/pH.

Due to its efficiency and relatively low capital demanding, many wastewater treatment plants have applied chlorination for disinfection of treated wastewater before discharging it. However, determination of optimal doses of chlorine for chlorination and sulfite for dechlorination, which removes residual chlorine, should made to guarantee complete destruction of microorganisms in treated wastewater and to protect aquatic life in a receiving stream. In this study, a new ORP/pH based approach to determine endpoints of breakpoint chlorination and of dechlorinating titration and to optimize doses of chlorine and sulfite. In this new method, significant points on the ORP and pH profiles occurring during the titrations for chlorination and dechlorination were utilized to determine chlorine demand and sulfite dosage.

Chlorine↗

PubMed2006

New ORP/pH based control strategy for chlorination and dechlorination of wastewater: pilot scale application.

Due to its efficiency and low capital demands, chlorination has been widely used for disinfection in many wastewater treatment plants. Since the oxidation power of free chlorine is bigger than combined chlorines which are formed from the reaction between chlorine and reducing agents in water (especially, NH4+ and organic nitrogen), for effective disinfection, excess amount of chlorine is added until all the reducing agents are oxidized and free chlorine is available. After chlorination, chlorine residues in wastewater are usually reduced with SO2 or sulfites before the treated wastewater is discharged, since they are toxic to aquatic life. Addition of excess amount of SO2 or sulfite should be avoided. Otherwise, they consume dissolved oxygen in a river or stream and may have adverse impact on the aquatic life. Determination of wastewater chlorine demand and of sulfite dosages for dechlorination has been a challenge to WWTP operators, due to the dynamic characteristics of wastewater. Recently, a new ORP/pH based approach to determine chlorine demand and sulfite dosage was proposed. The method utilizes significant points occurring on the pH and ORP profiles during chlorination and dechlorination titrations. In this study, the proposed automatic titration system has been implemented into a control system to optimize chlorine and sulfite doses for a pilot scale chlorination/dechlorination system. In short, the disinfection system with the pH/ORP based controller showed very successful results; complete inactivation of total coliforms, and almost zero residual chlorines and high DO in its effluent.

Chloramines↗

PubMed2005

Fabrication of large number density platinum nanowire arrays by size reduction lithography and nanoimprint lithography.

Large number density Pt nanowires with typical dimensions of 12 microm x 20 nm x 5 nm (length x width x height) are fabricated on planar oxide supports. First sub-20 nm single crystalline silicon nanowires are fabricated by size reduction lithography, and then the Si nanowire pattern is replicated to produce a large number of Pt nanowires by nanoimprint lithography. The width and height of the Pt nanowires are uniform and are controlled with nanometer precision. The nanowire number density is 4 x 10(4) cm(-1), resulting in a Pt surface area larger than 2 cm(2) on a 5 x 5 cm(2) oxide substrate. Bimodal nanowires with different width have been generated by using a Pt shadow deposition technique. Using this technique, alternating 10 and 19 nm wide nanowires are produced.

Journal Article↗

PubMed2002

Impact of surface heterogeneity on mercury uptake by carbonaceous sorbents under UHV and atmospheric pressure.

Chemical and morphological heterogeneities of carbon sorbents play important roles in gas-phase adsorption. However, the specific chemical complexes and topological structures of carbon that favor or impede elemental mercury uptake are not well understood and are the subject of this study. Temperature programmed desorption (TPD) with a model carbonaceous material (highly oriented pyrolytic graphite, HOPG) under ultrahigh vacuum (UHV) conditions and fixed bed adsorption by activated carbon (BPL) at atmospheric pressure were combined to investigate the effects of chemical and morphological heterogeneities on mercury adsorption by carbonaceous surfaces. TPD results show that mercury adsorption at 100 K onto HOPG surfaces with and without chemical functional groups and topological heterogeneity created by plasma oxidation occurs through physisorption. The removal of chemical functionalities from the HOPG surface enhances mercury physisorption. Plasma-oxidation of HOPG provides additional surface area for mercury adsorption. However, the pits created by plasma oxidation are more than 10 nm in diameter and do not simulate microporosity that predominates in activated carbons. Mercury adsorption by activated carbon at atmospheric pressure occurs through two distinct mechanisms. Physisorption governs mercury adsorption at lower temperatures (i.e., below 348 K), while chemisorption predominates at high adsorption temperatures (i.e., above 348 K). Presence of water on activated carbon surface enhances mercury uptake by both physisorption and chemisorption. Oxygen containing functional groups reduce mercury uptake by physisorption by blocking access to the micropores. No significant impact of oxygen functionalities was observed in the chemisorption regime. The key findings of this study open the possibility to apply scientific information obtained from the studies with simple surfaces such as HOPG under ideal conditions (UHV) to industrial sorbents under realistic process conditions.

Adsorption↗

PubMed2001

Microinjection of arginine vasopressin into the central nucleus of amygdala suppressed nociceptive jaw opening reflex in freely moving rats.

This study was performed to examine the antinociceptive effect after microinjection of arginine vasopressin (AVP) into the central nucleus of amygdala. We recorded the jaw opening reflex in freely moving rats. After injection of 0.2 or 0.4 nM AVP into the central nucleus of amygdala, digastric electromyogram (dEMG) was suppressed to 55 +/- 5% or 88 +/- 3 of the control. Artificial cerebrospinal fluid had no effects on the basal dEMG activity. V(1) vasopressin receptor antagonist blocked the suppressive effect produced by microinjection of 0.4 nM AVP from 53 +/- 3 to 81 +/- 3% of the control. However, V(2) vasopressin receptor antagonist did not affect changes in dEMG. We observed dEMG activity after intracerebroventricular injection of naloxone, methysergide, or phentolamine. All drugs did not affect the basal dEMG activity at our dose. Naloxone blocked the suppressive effect of 0.4 nM AVP from 42 +/- 4 to 79 +/- 5% of the control. Methysergide also inhibited the suppression of dEMG from 44 +/- 3 to 83 +/- 6% of the control. However, phentolamine, an alpha-adrenergic receptor antagonist, did not affect the suppression of dEMG. These results indicate AVP in the central nucleus of amygdala has potent analgesic effects in the orofacial area. The antinociception of central AVP seems to be mediated by opioid and serotonergic pathways.

Adrenergic alpha-Antagonists↗

PubMed2001

High-rate continuous production of lactic acid by Lactobacillus rhamnosus in a two-stage membrane cell-recycle bioreactor.

It is important to produce L(+)-lactic acid at the lowest cost possible for lactic acid to become a candidate monomer material for promising biodegradable polylactic acid. In an effort to develop a high-rate bioreactor that provides high productivity along with a high concentration of lactic acid, the performance of membrane cell-recycle bioreactor (MCRB) was investigated via experimental studies and simulation optimization. Due to greatly increased cell density, high lactic acid productivity, 21.6 g L(-1) h(-1), was obtained in the reactor. The lactic acid concentration, however, could not be increased higher than 83 g/L. When an additional continuous stirred tank reactor (CSTR) was attached next to the MCRB a higher lactic acid concentration of 87 g/L was produced at significant productivity expense. When the two MCRBs were connected in series, 92 g/L lactic acid could be produced with a productivity of 57 g L(-1) h(-1), the highest productivity among the reports of L(+)-lactic acid that obtained lactic acid concentration higher than 85 g/L using glucose substrate. Additionally, the investigation of lactic acid fermentation kinetics resulted in a successful model that represents the characteristics of lactic acid fermentation by Lactobacillus rhamnosus. The model was found to be applicable to most of the existing data with MCRBs and was in good agreement with Levenspiel's product-inhibition model, and the Luedeking-Piret equation for product-formation kinetics appeared to be effective in representing the fermentation kinetics. There was a distinctive difference in the production potential of cells (cell-density-related parameter in Luedeking-Piret equation) as lactic acid concentration increases over 55 g/L, and this finding led to a more precise estimation of bioreactor performance.

Bioreactors↗

PubMed2001

RNA localization: SHEdding light on the RNA-motor linkage.

Specific mRNAs achieve an asymmetric distribution in the cell by linking to molecular motors that walk along the cytoskeleton. Studies in S. cerevisiae have begun to define the nature of the RNA-motor linkage and identify She3p as an adaptor protein that links a type V myosin motor to specific ribonucleoproteins.

DNA-Binding Proteins↗

PubMed2001

Characterization of a novel gene expressed in neuromuscular tissues and centrosomes in Caenorhabditis elegans.

The nematode Caenorhabditis elegans has many advantages for studying gene function at the organism level. In particular, completion of the genome sequencing has made it feasible to study gene structure and function of both known and novel proteins. As a result of a database search for muscle-specific genes, a gene F43D9.1 was found which showed muscle-specific expression as revealed by the in situ hybridization pattern from the Expressed Sequence Tag (EST) database. A homology search of F43D9.1 protein sequences showed no significant homology with other known proteins, except that it showed very weak sequence similarity with the band 4.1 protein superfamily. Northern blot analysis reveals a single transcript 3.7 kb in size which is consistent with the predicted gene structure. The expression pattern of F43D9.1 was investigated using the gfp reporter gene, and it has shown to be expressed in neuronal cells including sensory neurons and interneurons in the head region. To further characterize F43D9.1, whole-mount immunostaining was performed with anti-F43D9.1 antibody, which showed specific signals in head neurons, body-wall muscle cells, some other unidentified neuronal cells, and centrosomes of the dividing cells during embryogenesis. Taken together with its predicted membrane topology, we speculate that the F43D9.1 gene, which encodes a novel transmembrane protein and contains a band 4.1-like domain, may function in neuromuscular cells, and may play an important role during cell division in C. elegans.

Amino Acid Sequence↗

PubMed2001

Mechanisms of synergistic cytokine-induced nitric oxide production in human alveolar epithelial cells.

Nitric oxide (NO) derived from inducible NO synthase (iNOS) at sites of inflammation is closely related to host defense against infection and airway inflammation. Cytokines are known to stimulate NO production in human alveolar epithelial cells in a synergistic (nonlinear or nonadditive) manner. The mechanism of this synergy is not known. We measured the activation of the transcription factor NF-kappaB, the iNOS protein, and NO production in A549 monolayers (human alveolar epithelial cell line) in response to different combinations of IL-1beta, INF-gamma, and TNF-alpha (100 ng/ml), and the cofactors FMN, FAD, and BH4. We found that both IL-1beta and TNF-alpha could independently activate cytosolic NF-kappaB, direct its translocation into the nucleus, and induce iNOS monomer synthesis. In addition, different combinations of cytokines produced synergistic amounts of iNOS monomers. Exogenous BH4 (0.1 microM) had no impact on NO production induced by cytokine combinations that included IL-1beta, but significantly enhanced NO production in the presence of INF-gamma and TNF-alpha, and allowed TNF-alpha independently to produce NO. We conclude that there are at least three mechanisms of synergistic cytokine-induced NO production: (1) the biosynthesis of iNOS monomer due to nonlinear interactions by transcription factors, (2) synergistic cytosolic activation of NF-kappaB, and (3) parallel biosynthesis of BH4 in the presence of cytokine combinations that include IL-1beta.

Arginine↗

PubMed2001

Clinical spectrum of reversible posterior leukoencephalopathy syndrome.

Reversible posterior leukoencephalopathy syndrome is a recently recognized disorder with characteristic radiologic findings that mainly involve the white/gray matter of the parieto-occipital lobes. This complex syndrome is associated with cyclosporine A therapy or a variety of other conditions in which blood pressure rises acutely. Twelve patients from a variety of conditions who met the diagnostic criteria for this syndrome were studied. Interestingly, three of these patients had intra-abdominal neurogenic tumors, which have rarely been reported. Initial cranial magnetic resonance imaging scans revealed fairly symmetric areas of increased T(2) signal involving both white and gray matter of parieto-occipital lobes in the majority of the patients. However, the lesions were often located outside the parieto-occipital regions. Four patients had occipital region magnetic resonance spectroscopy during the acute phase, which revealed high lactate peak and normal N-acetyl aspartate/creatine and choline peaks. With appropriate treatment, most patients recovered from this syndrome and experienced almost complete resolution of brain lesions on follow-up magnetic resonance imaging. One patient, however, continued to have small residual hemosiderin deposits on a follow-up magnetic resonance imaging with neurologic sequellae. In conclusion, a better understanding of this complex syndrome may obviate unnecessary investigations and allow management of the associated problems in prompt and appropriate ways.

Adolescent↗

PubMed2001

The validity and reliability of the GAITRite system's measurements: A preliminary evaluation.

OBJECTIVE: To compare the concurrent validity and reliability of the GAITRite computerized gait analysis system with validated paper-and-pencil and video-based methods. DESIGN: Within-groups, repeated-measures design. SETTING: Research laboratory in a physical therapy education program. PARTICIPANT: One healthy woman, age 27 years. INTERVENTIONS: A subject walked across the walkway of the GAITRite system at various walking rates and degrees of step symmetry for 2 of the 3 analyses. Paper placed over the walkway enabled concurrent paper-and-pencil analysis. The subject was concurrently videotaped from the side. For the other analysis, a stride simulator with known step and stride lengths was applied to the walkway to simulate 2 steps and 1 stride. MAIN OUTCOME MEASURES: Cadence, walking speed, right and left step and stride lengths, and right and left step times. RESULTS: Excellent paper-and-pencil and GAITRite correlations (intraclass correlation coefficient [ICC] > 95) for spatial measures and excellent video-based and GAITRite correlations (ICC > 93) for temporal measures were found. GAITRite measures of step lengths and times were reliable in both walkway center and left-of-center measurements. CONCLUSIONS: Based on this data, GAITRite is a valid and reliable tool for measuring selected spatial and temporal parameters of gait.

Adult↗

PubMed2001

Correction of sunken and/or multiply folded upper eyelid by fascia-fat graft.

Sunken and/or multiply folded upper eyelid is one of the common, troublesome complications that can occur after Oriental blepharoplasty. In addition to orbital volume depletion, the traumatic surgical procedure of excessive fat removal might result in a varying degree of adhesion and injury to the orbital septum. Adhesiotomy followed by a restoration of volume is generally believed to be the logical way to correct such deformity. To restore volume and prevent re-adhesion, local tissues of the upper eyelid, free-fat graft, and dermis-fat graft have been used. However, local tissues are usually insufficient because of previous surgery, and the survival rate of grafted fat is often unpredictable. Moreover, the heaviness of the dermis-fat composite makes it a less than satisfactory choice. The authors value the use of free fascia-fat composite grafts for the treatment of such disfigurements. The fascia-fat composite is expected to have a better survival rate than free fat alone and to be lighter than a dermis-fat composite. In addition, the fascia-fat composite is abundant throughout the body and provides anatomical structure more similar to that of the repair site, namely, the damaged orbital septum and fat. The authors prefer the mons pubis, preauricular, and temporal areas for the donor site depending on the status of the damage. They treated 13 patients with sunken and/or multiply folded upper eyelids by fascia-fat composite grafts and obtained satisfactory results.

Adipose Tissue↗

PubMed2001

Metschnikowia lochheadii and Metschnikowia drosophilae, two new yeast species isolated from insects associated with flowers.

Two new haplontic heterothallic species of Metschnikowia were isolated from floricolous insects and flowers. Metschnikowia lochheadii was recovered from insects found in various flowers on the Hawaiian Islands of Kauai and Maui, and from Conotelus sp. (Coleoptera: Nitidulidae) in northwestern Guanacaste Province, Costa Rica. The morphology, physiology, and sexual cycle are typical of the large-spored Metschnikowia species, and the partial ribosomal DNA large subunit (D1D2) sequences suggest that the new species is most closely related to Candida ipomoeae. Metschnikowia lochheadii is nearly indistinguishable from its ascogenous relatives and conjugates freely with Metschnikowia continentalis, forming sterile asci. It also exhibits asymmetric mating with Metschnikowia hawaiiensis. Metschnikowia drosophilae was found in morning glory (Ipomoea sp.) flowers and associated Drosophila bromeliae on Grand Cayman Island. Its nutritional profile is atypical of the genus, being the only species that does not utilize sucrose or maltose as carbon sources, and one of the few that does not utilize melezitose. D1D2 sequences show that Metschnikowia drosophilae is a sister species to Candida torresii, to which it bears considerable similarity in nutritional profile. The type cultures are: Metschnikowia lochheadii, strains UWO(PS)00-133.2 = CBS 8807 (h+, holotype) UWO(PS)99-661.1 = CBS 8808 (h-, isotype); and Metschnikowia drosophilae, strains UWO(PS)83-1135.3 = CBS 8809 (h+, holotype) and UWO(PS)83-1143.1 = CBS 8810 (h-, isotype).

Animals↗

PubMed2001

Inhibition by clonidine of the carbachol-induced tension development and nonselective cationic current in guinea pig ileal myocytes.

Effects of clonidine, an imidazoline derivative as well as alpha2-adrenoceptor agonist, on carbachol (CCh)-evoked contraction in guinea pig ileal smooth muscle were studied using isometric tension recording. To investigate the cellular mechanisms of the inhibitory effect of clonidine, its effects on CCh-evoked nonselective cationic current (I(CCh)), voltage-dependent Ca2+ current (I(Ca)) and voltage-dependent K+ current (I(K)) was also studied using patch-clamp recording techniques in single ileal cells. Clonidine inhibited the contraction evoked by CCh (1 microM) in a concentration-dependent manner with an IC50 valve of 61.7 +/- 2.5 microM. High K+ (40 mM)-evoked contraction was only slightly inhibited even when clonidine was used at 300 microM. Externally applied clonidine inhibited I(CCh) dose-dependently with an IC50 of 42.0 +/- 2.6 microM. When applied internally via patch pipettes, clonidine was without effect. An I(CCh)-like current induced by GTPgammaS was also inhibited by bath application of clonidine. None of KU14R and BU224, both imidazoline receptor blockers, and yohimbine, an alpha2-adrenergic blocker, significantly affects the inhibitory effect of clonidine on I(CCh). Clonidine (300 microM) only slightly decreased membrane currents flowing through voltage-gated Ca2+ channels or K+ channels. These data indicate that clonidine relaxes smooth muscle contraction produced by muscarinic receptor activation and suggest that the effect of clonidine seems due mainly to inhibition of I(CCh) via acting directly on the involved cationic channel.

Adrenergic alpha-Agonists↗

PubMed2001

Mechanism of carbon monoxide-induced relaxation in the guinea pig ileal smooth muscle.

The mechanism of carbon monoxide (CO)-induced relaxation were investigated in the guinea-pig ileum. CO (10%) inhibited the 40 mM KCl-induced contraction. This effect was antagonized by ODQ (1 microM), a soluble guanylate cyclase inhibitor. In contrast, CO did not inhibit the 40 mM KCl-induced increase in cytosolic Ca2+ level ([Ca2+]i). Cumulative addition of KCl induced a graded increase in both [Ca2+]i and muscle tension. In the presence of CO, the increase in muscle tension was attenuated whereas the increase in [Ca2+]i was only slightly decreased. Thus, the [Ca2+]i-tension relationship constructed by cumulative addition of KCl shifted downwards in the presence of CO. Using the patch clamp, CO was found to have little effect on the peak Ba currents (I(Ba)) when voltage was stepped from -60 mV to 0 mV. From these results, we conclude that CO inhibits contraction of guinea-pig ileum mainly by the decrease in the sensitivity of contractile elements to Ca2+ via a cyclic GMP-dependent pathway but not by the inhibition of L-type Ca2+ channel.

Animals↗

PubMed2001

Lysophosphatidylcholine decreases delayed rectifier K+ current in rabbit coronary smooth muscle cells.

Lysophosphatidylcholine (LPC), which exists abundantly in lipid fraction of oxidized low density lipoprotein, has been implicated in enhanced agonist-induced contraction and increase of intracellular Ca2+. The effect of LPC on the activity of delayed rectifier K+ current (I(dK)), which is a major determinant of membrane potential and vascular tone under resting condition, was examined in rabbit coronary smooth muscle cells using whole cell patch clamping technique. Application of LPC to the bath solution caused a concentration-dependent inhibition of I(dK), and the concentration to produce half-maximal inhibition was 1.51 microM. This effect of LPC on I(dK) was readily reversed after washout of LPC in the bath. The steady-state voltage dependence of I(dK) was shifted to positive direction by both extra- and intracellular application of LPC. Staurosporine (100 nM) pretreatment significantly suppressed the LPC-induced inhibition of I(dK). These results suggest that LPC inhibits I(dK) in rabbit coronary smooth muscle cells by a pathway that involves protein kinase C, and the LPC-induced inhibition of I(dK) may be, at least in part, responsible for the abnormal vascular reactivity in atherosclerotic coronary artery.

Animals↗

PubMed2001

Capsaicin-induced relaxation in rabbit coronary artery.

In the present study mechanism of inhibitory effects of capsaicin on the contractility of rabbit coronary artery were studied by measurement of isometric tension and intracellular Ca2+ concentration. Capsaicin (1 microM to 30 microM) relaxed the coronary artery pre-contracted with prostaglandin (PG) F2alpha (1 microM) in a concentration-dependent manner. The PGF2alpha-induced increase in intracellular Ca2+ concentration was also inhibited. The effects of capsaicin were readily reversed by washing capsaicin from the bath. Capsaicin-induced relaxation was not attenuated by pretreatment with capsazepine (1 microM), a blocker of vanilloid receptor or ruthenium red (1 microM), a blocker of non-selective cation channel. Previous exposure to a high concentration of capsaicin (100 microM) or repeated application of capsaicin did not eliminate the relaxation response to subsequent application of capsaicin. Increasing the external K+ concentration to 80 mM significantly attenuated the capsaicin-induced relaxation with simultaneous change in intracellular Ca2+ concentration. Pretreatment with iberiotoxin (100 nM), a blocker of Ca2+-activated K+ channel, only partially inhibited the capsaicin-induced relaxation. However, application of 4-aminopyridine (4-AP, 1 mM), a blocker of delayed rectifier K+ current significantly inhibited the capsaicin-induced relaxation with concomitant attenuation of the effect on intracellular Ca2+ concentration. These results indicate that capsaicin may have a direct relaxing effect on the smooth muscle contractility, and relaxation may be due to activation of the 4-AP-sensitive, delayed rectifier K+ channels in the rabbit coronary artery.

4-Aminopyridine↗