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Biomedical subjects

J Yoon

Publications and source records attributed to J Yoon.

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

Investigation of the reaction pathway of OH radicals produced by Fenton oxidation in the conditions of wastewater treatment.

Abstract Fenton reaction has been often used to treat industrial wastewater or landfill leachate. However, most mechanistic research into the Fenton reaction has been confined to low concentration conditions (usually the concentration of iron is less than 1 mM). These conditions are removed from the circumstances of real application. This is especially true in the treatment of landfill leachate in Korea. Therefore, we investigated the characteristics of the Fenton system using high concentrations of iron (mostly [Fe2+] = 1 approximately 10 mM, [H2O2] = 5 mM, [Organic (t-BuOH or methanol)] = 0 or 30 mM) and interpreted the results from the known reaction mechanisms of the Fenton system. As a result, the use of high ferrous ion (> or = 1 mM) is believed to be appropriate for producing large quantities of OH. within a short period of time, causing fast consumption of hydrogen peroxide. However, OH. scavenging by the ferrous ion, the changes of oxidation products due to the oxygen depleted conditions, and the precipitation effect of ferric ion must be considered for the successful application of Fenton reaction. On the other hand, in low ferrous ion (<1 mM), it is important to utilize the redox cycles of iron in an effective manner.

Chemical Precipitation↗
PubMed2001

Ultrasonographic observation of intestinal mobility of dogs after acupunctural stimulation on acupoints ST-36 and BL-27.

objectives of this study were to observe normal peristalsis and mixing (or segmental movements) and to evaluate an acupuncture stimulation (ST-36 and BL-27) on the intestinal (duodenum) motility in normal dogs using duplex Doppler sonography. Fifteen healthy Beagle dogs were used for this experiment after the administration of warm saline and pellet feeding. The duodenal motility was examined using duplex Doppler sonography. Six hours after the pellet feeding, an electroacupuncture stimulation at ST-36 and BL-27 was applied and the duodenal motility was examined using duplex Doppler sonography pre-stimulation, during the stimulation and post-stimulation. After saline and pellet administration, the duplex Doppler sonograms showed 3 types of peristalsis and a mixing type (or segmental movement) of duodenum motility. In the peristalsis types, most yielded high-amplitude signals which had one high peak (type-1), two high peaks (type-2), and three high peaks (type-3) and lasted more than 1.3 seconds. Mixing type of duodenum motility had weak signals and were lasted more than 1.5 seconds. Among the peristalsis types, the type 1 and type 2 were predominant and the type 3 was rarely observed. The frequency of intestinal motility stimulated by ST-36 acupoint was increased during the acupuncture stimulation (20% increase compared to the basal value) and decreased (7% decrease compared to the basal value) after stimulation. The frequency of intestinal motility stimulated by BL-27 acupoint was decreased during the acupuncture stimulation (31% decrease compared to the basal value) and increased (18% increase compared to the basal value) after stimulation. There was a significant increase between the value found in during and the post-stimulation tests. We conclude that duplex Doppler studies permit a graphic visualization of intestinal movements which can be qualitatively and quantitatively analyzed using this technique, it is possible to evaluate the gastrointestinal motility after an acupuncture

Acupuncture Points↗
PubMed2001

Application of pulsed Doppler ultrasound for the evaluation of small intestinal motility in dogs.

The purpose of this study was to verify whether small intestinal peristalsis could be observed and quantitatively assessed using pulsed-Doppler ultrasound. Pulsed-Doppler ultrasound was used to evaluate small intestinal peristalsis after a meal in ten normal dogs and ten sedated dogs. The small intestinal peristalses were measured 0, 1, 3, 6, 9, 12, and 24 hours after a 24-hour fast and after feeding. The number of small intestinal peristalsis were 0.133/min, 0.100/min, 0.033/min, 0.167/min, 0.070/min, 0.067/min, and 0.100/min in the fasted dogs, and 1.667/ min, 0.933/min, 1.133/min, 1.234/min, 1.933/min, 1.533/ min, and 0.533/min in fed dogs, respectively. In the dogs sedated with xylazine HCl, the number of small intestinal peristalsis was significantly reduced (p<0.01). However, in the dogs treated with ketamine HCl and acepromazine, the number of small intestinal peristalsis remained unchanged. Therefore, it can be concluded that pulsed-Doppler ultrasound allows graphic visualization of the intestinal movements, which can be subjected to qualitative and quantitative analysis, and may be suitable for a non-invasive study of small intestinal motility.

Acepromazine↗
PubMed2000

Synthesis and Surface-Active Properties of New Photosensitive Surfactants Containing the Azobenzene Group.

Several water-soluble cationic surfactants, 4-alkylazobenzene-4'-(oxy-2-hydroxypropyl)trimethylammonium methylsulfate (AZMS) (AZMS-0, AZMS-1, AZMS-2, AZMS-4, and AZMS-8), containing alkylglycidylether and azoarene have been synthesized with high yields of 63-78% and their surface-active properties have been investigated upon irradiation with UV/vis light. All of the trans-AZMS surfactants are isomerized to cis-trans mixtures containing 92.5% cis isomer by UV light irradiation at 350 nm. The cis isomers in the mixtures are reverted to trans isomers by visible light irradiation (lambda>445 nm). Such photoisomerization induces changes in the surface activity of each surfactant. The critical micelle concentration (cmc) of the trans form of AZMS-8 surfactant is about 1.28x10(-4) mol/l. At the photostationary state, 92.5% of the trans form is changed to the cis form which exhibits a slightly higher cmc (3.41x10(-4) mol/l). The new cmc of AZMS surfactants upon photoisomerization is similar to that of the ideal mixed micellar system. In particular, the ratio of cmc(cis) to cmc(trans) of AZMS derivatives is about 1.87-2.85 which increases proportionally with the chain length of alkyl group. The minimum average area per molecule (A(min)(a/w)) for the trans and cis isomers of AZMS-8 is 0.60 and 0.74 nm(2), respectively. The difference in the A(min)(a/w) may originate from the structural differences in the two isomers. These values are quite different as compared to those of the conventional azobenzene surfactants. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

The DNA replication-related element (DRE)-DRE-binding factor (DREF) system may be involved in the expression of the Drosophila melanogaster TBP gene.

The TATA box binding protein (TBP) is a general transcription factor required for initiation by all three eukaryotic RNA polymerases. Previously, we found that the promoter region of the Drosophila melanogaster TBP gene contains three sequences similar to the DNA replication-related element (DRE) (5'-TATCGATA). In the present study, we found that the DRE-like sequences are also present in the promoter of the Drosophila virilis TBP gene, suggesting a role for these sequences in TBP expression. Band mobility shift assays revealed that oligonucleotides containing sequences similar to the DRE of D. melanogaster TBP gene promoter form specific complexes with a factor in a Kc cell nuclear extract and with recombinant DRE-binding factor (DREF). Furthermore, these complexes were either supershifted or diminished by monoclonal antibodies to DREF. Transient luciferase assays demonstrated that induction of mutations in two DRE-related sequences at positions -223 and -63 resulted in an extensive reduction of promoter activity. Thus, the DRE-DREF system appears to be involved in the expression of the D. melanogaster TBP gene.

Animals↗
PubMed2000

Structure, chromosomal localization, and expression of the Drosophila melanogaster gene encoding sepiapterin reductase.

We have isolated and characterized a Drosophila melanogaster gene encoding the sepiapterin reductase (SR). The gene does not have introns. The 5'- and 3'-RACE analysis, which determined the transcription start point (tsp) and polyadenylation site, respectively, showed that the gene produces single mRNA species. The potential promoter region lacks distinct TATAAA or CCAAT box consensus sequences. RNA blot analysis revealed that the gene encodes a 1.4kb transcript that could be detected throughout development and in both heads and bodies of adults. The Drosophila SR gene maps to 15A on the X chromosome.

Alcohol Oxidoreductases↗
PubMed2000

Parallel solid-phase synthesis of vitronectin receptor (alphavbeta3) inhibitors.

A combinatorial approach for rapid optimization of a vitronectin receptor (alphavbeta3) inhibitor lead was accomplished by solid-phase synthesis. Orthogonally bis protected 2,3-diaminopropionic acid was used to immobilize the C-terminus of the molecule. Selective deprotection and functionalization of the alpha-amino group followed by acyl resorcinol scaffold attachment and N-terminus diversification was used to explore structure activity relationship (SAR).

Receptors, Vitronectin↗
PubMed2000

NMR studies on novel antitumor drug candidates, deoxoartemisinin and carboxypropyldeoxoartemisinin.

Artemisinin and its derivatives, which have been known as antimalarial drugs, have also demonstrated their cytotoxicity against tumor cells. It has been proposed that antitumor activity depends on the lipophilicity of functional group on artemisinin derivatives. Solution structures of two artemisinin derivatives as antitumor drug candidates, deoxoartemisinin and carboxypropyldeoxoartemisinin, were determined by NMR spectroscopy to elucidate structure-activity relationship. According to biological assay, antitumor efficiencies are not dependent upon lipophilicity. Instead, these compounds demonstrated their distinctive structural features of boat/chair conformation and capability to interact with receptors, as they have different efficiencies on antitumor activity. Especially, carboxypropyl moiety or carbonyl moiety in artemisinin derivatives influences the conformation and stability of ring structure. Although the detailed mechanism of antitumor activity by artemisinin derivatives has not been addressed, we suggest that antitumor activity is not determined only with lipophilicity and that artemisinin derivatives have specific target proteins in each type of cancer.

Animals↗
PubMed2000

Efficient syntheses and ring-opening reactions of trans- and cis-oxazoline-5-carboxylates

[formula: see text] cis- and trans-Oxazoline-5-carboxylates were synthesized efficiently from isopropyl trans-cinnamate utilizing the Sharpless AA reaction. trans-Oxazoline was much more reactive than the cis-isomer toward ring opening reactions. From ab initio molecular calculations, the cis-isomer was predicted to be less reactive than the trans-isomer by 2.7 kcal/mol. Both syn and anti acetylthio esters and anti diamino esters were synthesized from these cis- and trans-oxazoline-5-carboxylates.

Journal Article↗
PubMed2000

Novel mechanism of massive photoreceptor degeneration caused by mutations in the trp gene of Drosophila.

The Drosophila trp gene encodes a light-activated Ca(2+) channel subunit, which is a prototypical member of a novel class of channel proteins. Previously identified trp mutants are all recessive, loss-of-function mutants characterized by a transient receptor potential and the total or near-total loss of functional TRP protein. Although retinal degeneration does occur in these mutants, it is relatively mild and slow in onset. We report herein a new mutant, Trp(P365), that does not display the transient receptor potential phenotype and is characterized by a substantial level of the TRP protein and rapid, semi-dominant degeneration of photoreceptors. We show that, in spite of its unusual phenotypes, Trp(P365) is a trp allele because a Trp(P365) transgene induces the mutant phenotype in a wild-type background, and a wild-type trp transgene in a Trp(P365) background suppresses the mutant phenotype. Moreover, amino acid alterations that could cause the Trp(P365) phenotype are found in the transmembrane segment region of the mutant channel protein. Whole-cell recordings clarified the mechanism underlying the retinal degeneration by showing that the TRP channels of Trp(P365) are constitutively active. Although several genes, when mutated, have been shown to cause retinal degeneration in Drosophila, the underlying mechanism has not been identified for any of them. The present studies provide evidence for a specific mechanism for massive degeneration of photoreceptors in Drosophila. Insofar as some human homologs of TRP are highly expressed in the brain, a similar mechanism could be a major contributor to degenerative disorders of the brain.

Amino Acid Sequence↗
PubMed2000

Nodal and bone morphogenetic protein 5 interact in murine mesoderm formation and implantation.

Mice mutant for the TGF-beta family member, nodal, lack mesoderm and die between E8.5 and E9.5. The short ear-lethal (se(l) ) mutation, a deletion that eliminates Bmp-5, causes a strikingly similar gastrulation defect. Here we analyze se(l);nodal compound mutants and find a dosage effect. Embryos homozygous for one mutation show distinct gastrulation stage defects that depend on whether they are heterozygous or homozygous for the other mutation. Embryos mutant for nodal or se(l);nodal compound mutants fail to execute an antigenic shift indicative of mesoderm differentiation and ectoderm cells are shunted into an apoptotic pathway. Furthermore, we find a novel phenotype in se(l);nodal double mutant litters, in which two to four genetically different embryos are contained within the same deciduum. Both the gastrulation and implantation phenotypes can also arise in short ear-viable (se(v) ) and se(v); nodal mutant mice. These data indicate that loss of Bmp-5 may underlie the se(l) gastrulation phenotype and suggest that nodal and Bmp-5 interact during murine mesoderm formation. Our data also reveal an unsuspected role for Bmp-5 in implantation and the decidual response in the mouse.

Animals↗
PubMed2000

ENVIRONMENTAL AUDITING: Economic Values of Recreational Power Boating Resources in Pennsylvania.

/ The travel cost method was used to estimate the economic value of seven major power boating resources in Pennsylvania. A significant relationship between number of visitor trips and cost per visitor trip existed for five of the seven water bodies. The annual total value for those five resources was $396 million, which was 2.5 times greater than the total out-of-pocket expenditures of approximately $157 million visitors spent to visit them. Research results can help resource managers plan and craft programs and policies that are founded on economic values of the natural resources involved.

Journal Article↗
PubMed2000

Effects of electric stimulation on bovine oocyte activation and embryo development in intracytoplasmic sperm injection procedure.

PURPOSE: This study was carried out to investigate the efficacy of electric stimulation before and/or after intracytoplasmic sperm injection (ICSI) on bovine oocyte activation and embryo development. METHODS: The oocytes were treated with electric shock before (B), before and after (B&A), and after (A) sperm injection. In each group, sham ICSI (ICSI-s) was performed to exclude the effect of parthenogenesis (B ICSI-s, B&A ICSI-s, and A ICSI-s). An electric pulse was applied with a single direct current (DC) pulse (0.8 kV/cm, 70 microseconds). RESULTS: One pronucleus (PN) formation in the B&A ICSI-s group was slightly higher than that found in B and B&A ICSI group; however, the difference was not significant. Two PN formation in B&A ICSI group was higher than that found in sham ICSI groups (P < 0.05). There were no differences among treatment groups in the cleavage rate; however, morulae and blastocyst formation in the B&A embryos was significantly higher than that of other groups (P < 0.05) and got pregnant. CONCLUSIONS: Electric stimulation before and after injection was an effective method in inducing bovine oocyte activation and in sustaining embryo development to the morulae and blastocyst stage.

Animals↗
PubMed2000

Supervisor support in the work place: legitimacy and positive affectivity.

The authors tested 3 hypotheses regarding supervisor support in the work place. The validation hypothesis predicts that when employees are supported by their coworkers and the larger organization, they also receive more support from their supervisors. The positive affectivity hypothesis predicts that employees with positive dispositions receive more supervisor support because they are more socially oriented and likable. The moderation hypothesis predicts a joint multiplicative effect between validation and positive affectivity. An assessment of the hypotheses among a sample of 1,882 hospital employees in Korea provided strong support for the validation and moderation hypotheses.

Adult↗
PubMed2000

Identification, characterization, and mapping of expressed sequence tags from an embryonic zebrafish heart cDNA library.

The generation of expressed sequence tags (ESTs) has proven to be a rapid and economical approach by which to identify and characterize expressed genes. We generated 5102 ESTs from a 3-d-old embryonic zebrafish heart cDNA library. Of these, 57.6% matched to known genes, 14.2% matched only to other ESTs, and 27.8% showed no match to any ESTs or known genes. Clustering of all ESTs identified 359 unique clusters comprising 1771 ESTs, whereas the remaining 3331 ESTs did not cluster. This estimates the number of unique genes identified in the data set to be approximately 3690. A total of 1242 unique known genes were used to analyze the gene expression patterns in the zebrafish embryonic heart. These were categorized into seven categories on the basis of gene function. The largest class of genes represented those involved in gene/protein expression (25.9% of known transcripts). This class was followed by genes involved in metabolism (18.7%), cell structure/motility (16.4%), cell signaling and communication (9.6%), cell/organism defense (7.1%), and cell division (4.4%). Unclassified genes constituted the remaining 17.91%. Radiation hybrid mapping was performed for 102 ESTs and comparison of map positions between zebrafish and human identified new synteny groups. Continued comparative analysis will be useful in defining the boundaries of conserved chromosome segments between zebrafish and humans, which will facilitate the transfer of genetic information between the two organisms and improve our understanding of vertebrate evolution.

Animals↗