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YS Lee

Publications and source records attributed to YS Lee.

8 recordsLinked to original sources
PubMed2000

Embryo recovery and transfer for the production of transgenic goats from Korean native strain, Capra hircus aegagrus.

During the breeding season in Korea (September 1997 to April 1998), a goat embryo recovery and transfer program using a Korean native strain (Capra hircus aegagrus) was performed for the production of transgenic goats. Donors were synchronized with norgestomet implants and superovulated by a combined treatment with FSH and hCG. The treatment regime induced a consistent and efficient superovulation rate of 90% from donors with an ovulation rate of 12.1+/-0.5. 50.5% of the recovered oocytes/embryos were fertilized and most of them were at the 1-cell stage. After DNA microinjection, a total of 188 embryos were immediately transferred to naturally cycling or hormonally synchronized recipients with two or three embryos per animal. There was a tendency for the pregnancy rate of naturally cycling recipients to be higher (38.9%) than that of hormonally synchronized recipients (25.7%). When the recipients were classified into a two or three embryo-received group, the embryo viability was markedly decreased from 58.3% in two embryo-received group to 35.3% in three embryo-received group, without an increase in the kidding rate. This resulted from a high occurrence of abortions or stillbirths from the multiple-pregnant recipients which had received three embryos. This indicated that the transfer of two embryos per recipient is highly recommendable for an optimal embryo survival in Korean goats. Altogether, 188 embryos were transferred to 71 recipients and two transgenic Korean goats were produced from 25 offspring.

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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.

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PubMed2000

Electroosmotic Flow of a General Electrolyte Solution through a Fibrous Medium.

The electroosmotic flow of a general electrolyte solution through a fibrous medium is modeled theoretically taking the effect of double-layer polarization into account. The result obtained is applicable to an arbitrary level of electrical potential. We show that if the effect of double-layer polarization is neglected using the linearized Poisson-Boltzmann equation will underestimate electroosmotic velocity. The deviation becomes inappreciable, however, if kappaa is either very large or very small, kappa and a being, respectively, the reciprocal Debye length and the radius of a fiber. If the surface potential is high, the variation of electroosmotic velocity as a function of kappaa may exhibit a local maximum and a local minimum, and the larger the porosity of the fibrous medium the lower the level of surface potential for the local extremals to occur. If kappaa is small, the effect of surface potential on the electroosmotic velocity is more significant than that of double-layer polarization, and the reverse is true if kappaa is large. Copyright 2000 Academic Press.

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PubMed1999

Dipyridamole TI-201 SPECT imaging in patients with myocardial bridging

PURPOSE: Exercise-induced myocardial perfusion abnormalities have been reported in patients with myocardial bridging, possibly by tachycardia-induced shortening of diastole. Dipyridamole TI-201 SPECT findings were evaluated in patients with myocardial bridging to assess perfusion abnormalities during dipyridamole stress. MATERIALS AND METHODS: Dipyridamole TI-201 SPECT images of 12 patients with myocardial bridging (> or = 50% systolic narrowing) were evaluated. The peak heart rate during dipyridamole stress was less than 110 beats/min in all patients. The control group was 118 patients with fixed left anterior descending artery (LAD) disease. RESULTS: Fourteen sites of systolic arterial narrowing were present in LAD: two in mid-LAD, seven in distal LAD, and five in septal branches. Dipyridamole TI-201 SPECT showed reversible perfusion defects in three of six sites with 50% to 70% systolic narrowing and seven of eight sites with more than 80% systolic narrowing. Overall, 71% (10 of 14) had a reversible perfusion defect. Five patients with septal branch compression had a perfusion defect in the midanteroseptal wall without an apical abnormality. In the control group, no patient had an isolated perfusion defect in the midanteroseptal wall or septal branch disease (5 of 12 compared with 0 of 118; P < 0.001). CONCLUSIONS: Perfusion abnormalities on dipyridamole TI-201 SPECT are observed in LAD or its branches in patients with high-grade myocardial bridging. Myocardial bridging may decrease coronary flow reserve but not necessarily via tachycardia. Isolated perfusion defects in the midanteroseptal wall may be a characteristic finding of septal branch compression, because a fixed lesion involving a septal branch only is rare.

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