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Y Kwon

Publications and source records attributed to Y Kwon.

At least 55 records · Page 3Linked to original sources
PubMed1996

Theoretical considerations on two equations for estimating the extent of absorption after oral administration of drugs.

PURPOSE: The amount of drug absorbed into portal blood after oral dosing (Dp.o,g) has been estimated using Fick's principle (Q-method), i.e., Dp.o,g = Qh x (AUCp.o,g--AUCp.o,c), where Qh is the portal blood flow rate, and AUCp.o,g and AUCp.o,c are the areas under the concentration-time curves of portal vein and systemic blood after oral dosing, respectively. However, this method may underestimate Dp.o,g, when the drug is subject to systemic intestinal elimination. An alternate equation (CL-method; Dp.o,g = CLs x AUCp.o,g) is described using a simple pharmacokinetic model, to estimate Dp.o,g in the presence of systemic intestinal elimination, where CLs is systemic clearance. METHODS: The model is composed of central, intestine and liver compartments, assuming that drug is eliminated by intestinal and/or hepatic pathways only. A comparison of both methods for estimating Dp.o,g was made using computer-simulation or experimental data of phenacetin from the literature. RESULTS: The simulation study demonstrated that the Q-method underestimated Dp.o,g in the presence of significant intrinsic intestinal clearance, compared to the CL-method. The similar results were observed using the experimental data of phenacetin. CONCLUSIONS: The CL-method can provide a better estimate of Dp.o,g, while the Q-method may underestimate Dp.o,g, when there is significant systemic intestinal elimination of drugs after oral administration. In addition, useful information for understanding the relationship between the extent of absorption and the first-pass effect by intestine and/or liver after oral dosing of drugs can be obtained from the present approach.

Administration, Oral↗
PubMed1996

Acute subdural hematoma caused by a ruptured giant intracavernous aneurysm: case report.

A case of a giant intracavernous carotid artery aneurysm that presented as an acute subdural hematoma is reported. The patient was initially treated unsuccessfully with endovascular aneurysmal embolization and subsequently underwent attempted microsurgical clipping with preservation of the parent artery. At operation, an angiogram showed occlusion of the parent vessel, and the aneurysm was trapped by occlusion of the internal carotid artery. The patient did well for 2 days postoperatively but then developed contralateral progressive hemiplegia and aphasia. Emergent subsequent exploration and middle cerebral artery embolectomy were performed, and the hemiplegia and aphasia resolved rapidly. At 2-year follow-up, the patient continues to do well. To our knowledge, this is the first reported case of a patient who survived an acute subdural hematoma caused by an intracavernous carotid artery aneurysm.

Acute Disease↗
PubMed1996

Long-term follow-up of stereotactic Gamma Knife radiosurgery in epilepsy.

From June 1990 to May 1995, 31 patients with epilepsy were treated by stereotactic Gamma Knife radiosurgery at the Asan Medical center. The effect of radiosurgery for epilepsy was assessed in 23 patients followed for longer than 1 year. The seizures were medically intractable in all patients: generalized in 13 cases, complex partial in 6 cases and partial in 4 cases. The duration of epilepsy ranged from 1 to 25 years, with a mean of 11.6 years. Electroencephalography and magnetic resonance imaging (MRI) were performed in all patients to identify and localize the seizure focus. The lesions on MRI were nonprogressive and less than 2.0 cm in diameter. At follow-up, 12 patients had an excellent result (class I according to Engel's classification). In 3 of these patients, antiepileptic medication was discontinued. In a further 2 patients, the seizure frequency decreased (class II and III). In the remaining 9 patients, the frequency of seizures was unchanged (class IV). Radiation-induced edema did not seem to affect the outcome with respect to seizure control. The role of radiosurgery in the treatment of epilepsy is still unclear. It is premature to draw any definite conclusions about its efficacy for intractable epilepsy in our series. However, even this small group certainly suggests the possibility of a new safe treatment method in selected patients.

Adolescent↗
PubMed1996

Hepatic uptake of choline in rat liver basolateral and canalicular membrane vesicle preparations.

Choline, an endogenous quaternary ammonium ion, is transported into the liver by both saturable and nonsaturable processes. The objective of the present investigation was to determine the driving force(s) for uptake of choline in rat liver basolateral membrane (blLPM) and canalicular membrane (cLPM) vesicles. Choline is transported into an osmotically sensitive intravesicular space in both blLPM and cLPM. Uptake of [3H]choline into both blLPM and cLPM exhibited temperature dependence (0 degree C vs. 37 degrees C). A valinomycin-induced inside-negative K+ diffusion potential significantly stimulated initial uptake of [3H]choline in both vesicles. Choline uptake in blLPM and cLPM was not stimulated in the presence of an inwardly directed sodium gradient or an outwardly directed H+ gradient, and ATP did not enhance choline uptake in cLPM. Choline itself and structurally similar derivatives, such as hemicholinium-3 and succinylcholine, inhibited [3H]choline uptake 11 to 92% (at 10-fold higher concentrations) in blLPM and cLPM. Other cations, including N1-methylnicotinamide, thiamine and d-tubocurarine, and cardioglycosides did not inhibit choline transport in either vesicle preparation. In addition, [3H]choline uptake into both blLPM and cLPM was enhanced when vesicles were preloaded with nonradiolabeled choline (trans-stimulation). Kinetic studies indicated that choline was transported into blLPM by both saturable and passive processes and into cLPM predominantly by a saturable process. These results suggest that the transport of choline is likely mediated by a potential-sensitive conductive pathway in both blLPM and cLPM. The electrogenic pathway in cLPM may play a role in the reabsorption of choline from bile.

Animals↗
PubMed1995

Poly (A) binding protein is bound to both stored and polysomal mRNAs in the mammalian testis.

RNA-binding proteins that bind to the 3' untranslated region of mRNAs play important roles in regulating gene expression. Here we examine the association between the 70 kDa poly (A) binding protein (PABP) and stored (RNP) and polysomal mRNAs during mammalian male germ cell development. PABP mRNA levels increase as germ cells enter meiosis, reaching a maximum in the early postmeiotic stages, and decreasing to a nearly nondetectable level towards the end of spermatogenesis. Most of the PABP mRNA is found in the nonpolysomal fractions of postmitochondrial extracts, suggesting that PABP mRNA is either inefficiently translated or stored as RNPs during spermatogenesis. Virtually all of the testicular PABP is bound to either polysomal or nonpolysomal mRNAs, with little, if any, free PABP detectable. Analysis of several specific mRNAs reveals PABP is bound to both stored (RNP) and translated forms of the mRNAs. Western blot analysis and immunocytochemistry indicate PABP is widespread in the mammalian testis, with maximal amounts detected in postmeiotic round spermatids. The presence of PABP in elongating spermatids, a cell type in which PABP mRNA is nearly absent, suggests that PABP is a stable protein in the later stages of male germ cell development. The high level of testicular PABP in round spermatids and in mRNPs suggests a role for PABP in the storage as well as in the subsequent translation of developmentally regulated mRNAs in the mammalian testis.

Animals↗
PubMed1995

Different cholesterol deposition in aorta of Dahl salt-sensitive rats and spontaneously hypertensive rats fed a high-cholesterol diet.

1. We compared the serum and aortic lipid levels in spontaneously hypertensive rats (SHR) and Dahl salt-sensitive rats (DSR) fed a high-cholesterol (HC) diet. 2. In SHR fed the HC diet, the serum cholesterol level significantly increased, but no aortic cholesterol deposition was observed. 3. The serum cholesterol level in DSR fed the HC diet markedly increased compared to that in DSR fed the basal diet, and this change was greater with the diet containing 8% NaCl than 0.4% NaCl. A significant increase in the content of aortic cholesterol, notably cholesteryl ester, was observed in only DSR fed the HC diet containing 8% NaCl. 4. These results suggest that the combination of hypercholesterolaemia with salt-induced hypertension acts as a greater risk factor for atherosclerosis than that with genetic hypertension.

Animals↗
PubMed1995

Comparison of the effects of hypercholesterolaemia on relaxation responses in aortas of spontaneously hypertensive rats and Dahl salt-sensitive rats.

1. We investigated the effects of hypercholesterolaemia on relaxation responses in thoracic aortas isolated from two different types of hypertensive rats; spontaneously hypertensive rats (SHR) and Dahl salt-sensitive rats (DSR). 2. All rats fed the high cholesterol diet for 8 weeks showed a significant increase in the serum cholesterol level. The high cholesterol diet did not change the blood pressure of SHR, but increased that of hypertensive DSR fed a high-salt diet. 3. In aortas of SHR, the high-cholesterol diet did not change the endothelium-dependent and -independent relaxation induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively. 4. In aortas of hypertensive DSR, the high-cholesterol diet notably reduced the ACh-induced relaxations and slightly reduced SNP-induced relaxation. 5. These results suggest that hypercholesterolaemia causes greater impairment of endothelium-dependent relaxation in rat aorta with salt-induced hypertension than genetic hypertension.

Acetylcholine↗
PubMed1995

Stereotactic Gamma Knife radiosurgery for the treatment of dystonia.

A case of dystonia treated with Gamma Knife radiosurgery is reported. A 37-year-old female patient had a history of tuberculous meningitis at the age of 10 and subsequently developed a left hemidystonia. MRI showed an old infarction in the right caudate nucleus, globus pallidus and putamen. Stereotactic Gamma Knife radiosurgery was employed to make a lesion in the right posteroventral globus pallidus. Postoperatively, the patient's condition improved. However, homonymous hemianopsia developed postoperatively.

Adult↗
PubMed1995

Gamma knife radiosurgery for malignant tumors.

Between May 1990, and June 1994, 79 patients with malignant tumors were treated radiosurgically using a Leksell gamma unit at Asan Medical Center. Of these patients, 57 were metastatic brain tumor, 12 were glioblastoma multiforme (GM), 4 were primitive neuroectodermal tumor, 3 were malignant germ cell tumor, 2 were recurrent lymphoma, and 1 was adenoid cystic carcinoma of the orbit. Among 57 patients with metastatic tumors, 28 patients harboring 60 tumors were followed clinically and radiographically. The median marginal dose for these tumors was 30 Gy and the median survival rate was 15 months. Twenty-one tumors disappeared and 32 tumors decreased in size during 2 to 6 months after radiosurgery on computed tomographic or magnetic resonance imaging scans. All 12 patients with GM were treated with conventional radiation (6,240 approximately 6,500 cGy) after surgical resection or biopsy prior to radiosurgery (13 approximately 15 Gy to margin). The results were varied. Radiosurgical treatment of two recurrent lymphomas and three recurrent mixed germ cell tumors after radiation and chemotherapy provided rapid clinical improvement with disappearance of the tumor. However, new lesions appeared in two lymphomas and one mixed germ cell tumor within 3 to 4 months. One patient with adenoid cystic carcinoma of the orbit, who was treated radiosurgically prior to resection, is alive without recurrence 31 months after the treatment. Gamma knife radiosurgery appears to be the best alternative method to surgical excision plus radiation therapy for single and multiple cerebral metastases. It also provides rapid palliation of symptoms due to recurrent malignant tumors. And it may have an adjuvant role in the treatment of some tumors delaying local recurrence, if given prior to resection. However, the preliminary results for the malignant gliomas were inconclusive.

Adult↗