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H K Shin

Publications and source records attributed to H K Shin.

At least 19 recordsLinked to original sources
PubMed2006

Host-assisted intramolecular vibrational relaxation at low temperatures: OH in an argon cage.

The vibrational relaxation of hydroxyl radicals in the A (2)Sigma(+) (v=1) state has been studied using the semiclassical perturbation treatment at cryogenic temperatures. The radical is considered to be trapped in a closest packed cage composed of the 12 nearest argon atoms and undergoes local translation and hindered rotation around the cage center. The primary relaxation pathway is towards local translation, followed by energy transfer to rotation through hindered-to-free rotational transitions. Free-to-free rotational transitions are found to be unimportant. All pathways are accompanied by the propagation of energy to argon phonon modes. The deexcitation probability of OH(v=1) is 1.3 x 10(-7) and the rate constant is 4.7 x 10(5) s(-1) between 4 and 10 K. The negligible temperature dependence is attributed to the presence of intermolecular attraction (>>kT) in the guest-host encounter, which counteracts the T(2) dependence resulting from local translation. Calculated relaxation time scales are much shorter than those of homonuclear molecules, suggesting the importance of the hindered and free motions of OH and strong guest-host interactions.

Journal Article↗
PubMed2006

Collision-induced dissociation of transition metal-oxide ions: dynamics of VO+ collision with Xe.

The collision-induced dissociation of VO(+) by Xe has been studied by the use of classical dynamics procedures on London-Eyring-Polanyi-Sato potential-energy surfaces in the collision energy range of 5.0-30 eV. The dissociation threshold behavior and the dependence of reaction cross sections on the collision energy closely follow the observed data with the threshold energy of 6.00 eV. The principal reaction pathway is VO(+) + Xe --> V(+)+ O + Xe and the minor pathway is VO(+) + Xe--> VXe(+) + O. At higher collision energies (E > 8.0 eV), the former reaction preferentially occurs near the O-V(+)...Xe collinear and perpendicular alignments, but the latter only occurs near the perpendicular alignment. At lower energies close to the threshold, the reactions are found to occur near the collinear configuration. No reaction occurs in the collinear alignment V(+)-O...Xe. The high and low energy-transfer efficiencies of the collinear alignments O-V(+)...Xe and V(+)-O...Xe are attributed to the effects of mass distribution. The activation of the VO(+) bond toward the dissociation threshold occurs through a translation-to-vibration energy transfer in a strong collision on a time scale of about 50 fs.

Journal Article↗
PubMed2005

Vibrational relaxation of molecular ions at low temperatures: O2(-) (v=1) + Ar.

The vibrational relaxation of oxygen molecular ions trapped in an argon cage in the temperature range 10-85 K has been studied using semiclassical procedures. The collision model is based on the trapped molecule undergoing the restricted motions (local translation and hindered rotation) in a cage formed by its 12 nearest argon neighbors in a face-centered cubic arrangement. At 85 K in the liquid argon temperature range, the relaxation rate constant of O2(-) (v=1) is 1130 s(-1). The rate constant decreases to 270 s(-1) at 50 K and to 3.90 s(-1) at 10 K in the solid argon temperature range. In the range 10-85 K, the rate constant closely follows the temperature dependence k proportional to T2.7. Energy transfer pathways for the trapped molecular ion are vibration to local translation, argon phonon modes, and rotation (both hindered and free).

Journal Article↗
PubMed2004

Vibrational relaxation of oxygen in an argon cage.

The vibrational relaxation of oxygen embedded in an argon cage through vibrational to local translation, rotation, and argon phonon modes has been studied using semiclassical procedures. The collision model is based on the trapped molecule undergoing the restricted motions (local translation and hindered rotation) in a cage formed by its twelve nearest argon neighbors in a face-centered-cubic structure. At 85 K in the liquid argon temperature range, the deexcitation probability of O(2)(v=1) is 5.8 x 10(-12) and the relaxation rate constant with the collision frequency from local translation is 23 s(-1). The rate constant decreases to 5.1 s(-1) at 50 K and to 0.016 s(-1) at 10 K in the solid argon temperature range. Transfer of the vibrational energy to local translation, rotation (both hindered and free), and argon phonon modes is the relaxation pathway for the trapped oxygen molecule.

Journal Article↗
PubMed2004

Efficacy of pre-emptive milrinone in off-pump coronary artery bypass surgery: comparison between patients with a low and normal pre-graft cardiac index.

OBJECTIVE: The effect of pre-emptive milrinone without bolus during off-pump coronary artery bypass surgery (OPCAB) was evaluated in two groups of patients with low and normal pre-graft cardiac index. METHODS: Eighty-two patients were divided into two groups based on their pre-graft cardiac index. Each group was randomly subdivided into two groups to receive either milrinone or normal saline. After the internal mammary artery was harvested, the infusion of milrinone, or normal saline was started and maintained until the end of the anastomosis. The haemodynamic variables were measured: just before the start of milrinone or normal saline after pericardiotomy (baseline value); 10 min after the tissue stabilizer had been applied for the anastomosis of left anterior descending artery, left circumflex artery and right coronary artery; and after the sternal closure. RESULTS: Milrinone reduced the extent of the decrease in cardiac index and stroke volume as well as the extent of the increase in systemic and pulmonary vascular resistance. The extent of the decrease in cardiac index and mixed venous oxygen saturation were greater in normal pre-graft cardiac index group than in low pre-graft cardiac index group regardless of milrinone infusion during anastomoses. The effect of milrinone on haemodynamics showed no significant difference between low and normal pre-graft cardiac index groups. CONCLUSIONS: Pre-emptive milrinone infusion without bolus effectively improved cardiac performance during OPCAB and was especially useful for patients with low pre-graft cardiac index to prevent the decrease in cardiac index and stroke volume index below the critical level.

Aged↗
PubMed2002

Typing of clinical isolates of Mycobacterium leprae and their distribution in Korea.

Although there is no genetic diversity in isolates of Mycobacterium leprae, the variance of tandem repeats in the rpoT gene was recently demonstrated. We have typed clinical isolates of M. leprae in Korea using difference of the tandem repeats in the rpoT gene. Among 69 patients, 65 Korean isolates (94.2%) demonstrated four copies of the 6 bp tandem repeat (GACATC) in the rpoT gene, and incidences of three copies were found in only two Koreans and two foreigners (2.9%, respectively).

Base Sequence↗
PubMed2001

Restoration of vasodilation and CBF autoregulation by genistein in rat pial artery after brain injury.

This study determined whether, after fluid percussion injury (FPI), tyrosine kinase activation is coupled to inhibition of K(+) channels and alteration in cerebral blood flow (CBF) autoregulation in the rat pial artery. Injury of moderate severity (2--2.5 atm) was produced by FPI in anesthetized rats equipped with a closed cranial window. The suppressed vasodilation of the pial arterioles to calcitonin gene-related peptide (CGRP) and levcromakalim (LMK) and altered lower limit of CBF autoregulation after FPI were restored by genistein but not by daidzein, an inactive analog. Vasodilation to S-nitroso-N-acetyl penicillamine (0.1--10 micromol/l) was, however, little influenced after FPI. The restored vasodilation was decreased by sodium orthovanadate, suggesting the reciprocal action of tyrosine phosphorylation and dephosphorylation. After FPI, CGRP-induced vasodilation restored by genistein (10 micromol/l) was strongly antagonized by iberiotoxin but not by glibenclamide, whereas LMK-induced vasodilation was, in contrast, inhibited by glibenclamide but not by iberiotoxin. Taken together, we suggest that, after FPI, activation of tyrosine kinase links the inhibition of K(+) channels to impaired autoregulatory vasodilation in response to acute hypotension and alteration in CBF autoregulation in the rat pial artery.

Animals↗
PubMed2001

4G/5G polymorphism of the plasminogen activator inhibitor-1 gene and insertion/deletion polymorphism of the tissue-type plasminogen activator gene in atherothrombotic stroke.

BACKGROUND AND PURPOSE: Decreased fibrinolytic capacity due to increased plasminogen activator inhibitor-1 (PAI-1) activity and decreased tissue-type plasminogen activator (t-PA) activity has been associated with hypertension or atherothrombotic disorders. The aims of this study were to observe associations of the genetic polymorphism for PAI-1 and t-PA with hypertension and atherothrombotic stroke, and to elucidate whether impaired fibrinolytic activity in atherothrombotic stroke was related to atherothrombosis per se or to other risk factors such as hypertension. METHODS: Patients with atherothrombotic stroke (n = 60), hypertension (n = 100), and control subjects (n = 100) were enrolled. We genotyped all subjects for 4G/5G polymorphism in the promoter region of the PAI-1 gene and the Alu-repeat insertion/deletion (I/D) polymorphism in intron h of the t-PA gene by polymerase chain reaction and endonuclease digestion. RESULTS: The frequency of the 4G/4G genotype of PAI-1 was significantly higher in the atherothrombotic stroke patients than the control subjects (41.7 versus 21%; p = 0.005), but not in the hypertensive subjects. There was a significant association between 4G/4G genotype of PAI-1 and atherothrombotic stroke (adjusted odds ratio = 3.11, 95% confidence interval 1.18-8.15), adjusting for age, sex, total cholesterol, low-density lipoprotein, triglyceride, and body mass index. However, the number of the I/I genotype of t-PA in the atherothrombotic stroke or hypertensive patients was virtually identical to the control subjects. CONCLUSION: Our results suggest that the 4G/4G genotype of the PAI-1 gene is significantly associated with an increased risk of atherothrombotic stroke. This finding also supports that impaired fibrinolytic activity in atherothrombotic stroke is related to atherothrombosis per se, but not to hypertension, one of the most important risk factors of atherothrombotic stroke.

Adult↗
PubMed2000

Implication of adenosine A2A receptors in hypotension-induced vasodilation and cerebral blood flow autoregulation in rat pial arteries.

This study aimed to evaluate the role for adenosine A2A receptors in the autoregulatory vasodilation to hypotension in relation with cerebral blood flow (CBF) autoregulation in rat pial arteries. Changes in pial artery diameters were observed directly through a closed cranial window. Vasodilation induced by adenosine was markedly suppressed by ZM 241385 (1 micromol/l, A2A antagonist) and alloxazine (1 micromol/l, A2B antagonist), but not by 8-cyclopentyltheophylline (CPT, 1 micromol/l, A1 antagonist). CGS-21680-induced vasodilation was more strongly inhibited by ZM 241385 (25.3-fold; P<0.05) than by alloxazine. In contrast, 5'-N-ethylcarboxamido-adenosine (NECA)-induced vasodilation was more prominently suppressed by alloxazine (12.0-fold; P<0.001) than by ZM 241385. The autoregulatory vasodilation in response to acute hypotension of the pial arteries was significantly suppressed by ZM 241385, but not by CPT and alloxazine. Consistent with this finding, the lower limit of CBF autoregulation significantly shifted to a higher blood pressure by 1 micromol/l of ZM 241385 (53.0+/-3.9 mm Hg to 69.2+/-2.9 mm Hg, P<0.01) and 10 micromol/l of glibenclamide (54.7+/-6.5 mm Hg to 77.9+/-4.2 mm Hg, P<0.001), but not by CPT and alloxazine. Thus, it is suggested that adenosine-induced vasodilation of the rat pial artery is mediated via activation of adenosine A2A and A2B receptors, but not by A1 subtype, and activation of adenosine A2A receptor preferentially contributes to the autoregulatory vasodilation via activation of ATP-sensitive K+ channels in response to hypotension and maintenance of CBF autoregulation.

Animals↗
PubMed2000

Needle thoracic sympathectomy for essential hyperhidrosis: intermediate-term follow-up.

BACKGROUND: Essential hyperhidrosis is a condition with excessive sweating localized to certain part of the body. A definitive cure can be obtained by upper thoracic sympathectomy. METHOD: Between June and October 1997, 117 patients with essential hyperhidrosis underwent needle thoracoscopic sympathectomy. Of the 94 patients, 42 were men and 52 women. Their ages ranged from 14 to 63 years, with a mean age of 23 years. RESULTS: There were no mortality or life-threatening complications. Symptomatic improvement was found in 95.7%. Compensatory hyperhidrosis was found in 71.2% of the patients, but in these compensatory hyperhidrosis were mostly tolerable. CONCLUSIONS: This therapeutic procedure is minimally invasive and very effective. Further development of the new device and surgical technique are expected to follow.

Adolescent↗
PubMed2000

Striatocapsular haemorrhage.

Haemorrhages in the striatocapsular area, or striatocapsular haemorrhages (SCHs), have been regarded as a single entity, although the area is composed of several functionally discrete structures that receive blood supply from different arteries. We analysed the morphological and clinical presentations of 215 cases of SCHs according to a new classification method we have designed on the basis of arterial territories. SCHs were divided into six types: (i) anterior type (Heubner's artery); (ii) middle type (medial lenticulostriate artery); (iii) posteromedial type (anterior choroidal artery); (iv) posterolateral type (posteromedial branches of lateral lenticulostriate artery); (v) lateral type (most lateral branches of lateral lenticulostriate artery); and (vi) massive type. The anterior type (11%) formed small caudate haematomas, always ruptured into the lateral ventricle, causing severe headache, and mild contralateral hemiparesis developed occasionally. The outcome was excellent. The middle type (7%) involved the globus pallidus and medial putamen, frequently causing contralateral hemiparesis and transient conjugate eye deviation to the lesion side. About 50% of the patients recovered to normal. The posteromedial type (4%) formed very small haematomas in the posterior limb of the internal capsule and presented with mild dysarthria, contralateral hemiparesis and sensory deficit, with excellent outcome in general. The posterolateral type (33%) affected the posterior half of the putamen and posterior limb of the internal capsule and presented with impaired consciousness and contralateral hemiparesis with either language dysfunction or contralateral neglect. The outcome was fair to poor but there were no deaths. The lateral type (21%) formed large elliptical haematomas between the putamen and insular cortex. Contralateral hemiparesis with language dysfunction or contralateral neglect developed frequently but resolved over several weeks. The clinical outcome was relatively excellent except when the haematoma size was very large. The massive type (24%) formed huge haematomas affecting the entire striatocapsular area. Marked sensorimotor deficits and impaired consciousness, ocular movement dysfunctions including the 'wrong-way' eyes were observed quite frequently. The outcome was very poor with a case fatality rate of 81%. The clinico-radiological presentations suggested its origin was the same as the posterolateral type.

Adult↗
PubMed2000

Role of adenosine A(2B) receptors in vasodilation of rat pial artery and cerebral blood flow autoregulation.

This study was aimed to investigate the underlying mechanism of vasodilation induced by the activation of A(2B) adenosine receptors in relation to cerebral blood flow (CBF) autoregulation. Changes in pial arterial diameters were observed directly through a closed cranial window. N(omega)-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor) significantly suppressed the concentration-dependent vasodilations induced by adenosine and 5'-N-ethylcarboxamido-adenosine (NECA) but not the vasodilation by CGS-21680 (A(2A)-receptor agonist). Moreover, NECA-induced vasodilation was suppressed by alloxazine (1 micromol/l) but not by ZM-241385 (1 micromol/l, A(2A) antagonist), which suggests mediation by A(2B)- receptor activation. Otherwise, the level of nitrite/nitrate was concentration dependently increased in the artificial cerebrospinal fluid (CSF) when adenosine and NECA were suffused over the cortical surface. L-NAME and alloxazine, but not ZM-241385, largely inhibited their releases. The lower limit of CBF autoregulation was little affected following pretreatment with L-NAME or alloxazine. Thus it is suggested that adenosine-induced vasodilation via activation of A(2B)-adenosine receptors of the rat pial artery is coupled to the production of nitric oxide, which contributes little to CBF autoregulation.

Animals↗
PubMed1999

Cytotoxic effects of the components in heat-treated mistletoe (Viscum album).

Major cytotoxic components were fractionated from Korean mistletoe and the changes of their cytotoxic effects caused by heat treatment were investigated. The high cytotoxicity of isolated lectin I completely disappeared by heating for 30 min. The fractions of viscotoxins and alkaloids maintained their activities even after heating for 60 and 180 min, respectively. The alkaloid fraction was more cytotoxic to tumor MSV cells than to non-tumor A31 cells and the activity pattern was not changed by heat treatment. The possible contributions of alkaloids and viscotoxins to the activities of heat-treated mistletoe extracts such as tea or decoctions are discussed.

3T3 Cells↗
PubMed1999

Bilateral intracranial vertebral artery disease in the New England Medical Center, Posterior Circulation Registry.

BACKGROUND: Previous studies of patients with bilateral intracranial vertebral artery (ICVA) disease were selective and retrospective. METHODS: We studied risk factors, vascular lesions, symptoms, signs, and outcomes in patients with bilateral ICVA disease among 430 patients in the New England Medical Center Posterior Circulation Registry. RESULTS: Forty-two patients had bilateral ICVA occlusive disease (18 had bilateral stenosis; 16, unilateral occlusion and contralateral stenosis; and 8, bilateral occlusion). The most common risk factors were hypertension (32/42 [76%]) and hyperlipidemia (22/42 [52%]). Sixteen patients (38%) had transient ischemic attacks (TIAs) only; 18 (43%), TIAs before stroke. Occlusive vascular disease also involved the basilar artery in 29 patients (69%), the extracranial vertebral arteries in 18 (43%), and the internal carotid arteries in 11 (26%). Only 6 patients had no other major vascular lesion. Cerebellar symptoms were common. Among 30 patients with infarction, 21 (70%) had proximal intracranial territory involvement, and 15 (50%) had distal territory involvement. The location of occlusive lesions in relation to posterior inferior cerebellar artery origins did not significantly influence prognosis. During follow-up, 31 patients had no symptoms or slight disability, 2 had progression, and 7 died. Among 7 patients with poor outcome, 6 also had basilar artery stenosis or occlusion and 5 had proximal and distal intracranial territory infarcts. CONCLUSIONS: Most patients with bilateral ICVA occlusive disease have hypertension, other major occlusive lesions, and TIAs before stroke. Short- and long-term outcomes are usually favorable, but patients with bilateral ICVA and basilar artery-occlusive lesions often have poor outcomes.

Academic Medical Centers↗
PubMed1999

Metabolism of cAMP to adenosine: role in vasodilation of rat pial artery in response to hypotension.

The purpose of this experiment was to examine whether the cAMP-adenosine pathway is implicated in the autoregulatory vasodilation in response to hypotension. Suffusion with cAMP (1-100 micromol/l) or adenosine (0.01-10 micromol/l) caused a sustained vasodilation of the resting pial arteries in a concentration-dependent manner. In contrast, N6,2'-O-dibutyryl-cAMP and 8-bromo-cAMP exerted a weak dilation at high concentration (100 micromol/l). The vasodilation to cAMP (1-100 micromol/l), adenosine (0.01-10 micromol/l), and hypotension was significantly reduced by pretreatment with 3,7-dimethyl-1-propargylxanthine (1 micromol/l), an A2 receptor antagonist, as well as 3-isobutyl-1-methylxanthine (3 micromol/l), an inhibitor of endo- and ectophosphodiesterase, 1, 3-dipropyl-8-p-sulfophenylxanthine (100 micromol/l), an inhibitor of ecto-5'-phosphodiesterase, or alpha,beta-methylene-adenosine 5'-diphosphate (100 micromol/l), an inhibitor of ecto-5'-nucleotidase. However, 8-cyclopentyltheophylline (1 micromol/l), an A1 antagonist, did not elicit a similar response. The increased release of adenosine when the cortical surface was suffused with cAMP (100 micromol/l) was significantly reduced by 3-isobutyl-1-methylxanthine, 1,3-dipropyl-8-p-sulfophenylxanthine, and alpha,beta-methylene-adenosine 5'-diphosphate (each 100 micromol/l). These results indicate that the cAMP-adenosine pathway as a viable metabolic mechanism is implicated in the production of adenosine in the rat pial artery and contributes to the regulation of vasodilation in response to hypotension.

Adenosine↗
PubMed1999

Thoracoscopic sympathetic surgery for hyperhidrosis.

Resectional surgery of sympathetic nerves has been known to be the most effective treatment for essential hyperhidrosis and the application of thoracoscopic electrocauterization has provided a minimally-invasive procedure with the least morbidity and a resultant higher satisfaction rate. This paper describes our experience on the 1,167 cases of thoracoscopic sympathetic surgery for the treatment of essential hyperhidrosis. A total of 1,167 patients (674 males (58%) and 493 females (42%), mean age of 26.4 years with palmar (930), craniofacial (190) or axillary (47) hyperhidrosis underwent thoracoscopic sympathetic surgery from July 1992 to March 1999. Since the T2-4 sympathectomy, first performed in July 1992 for a patient of palmar hyperhidrosis, the operative methods have been altered to achieve a higher satisfaction level with the least complication by adopting less invasive procedures. Our current standard procedures being performed are T3 and T2 clipping for palmar and craniofacial hyperhidrosis and T3,4 sympathicotomy for axillary hyperhidrosis, all using a 2 mm needle thoracoscope. As the surgical procedures have been transited to a less invasive method with limited resection using the newest endoscopic devices, the average operation time and complications such as Horner's syndrome and compensatory hyperhidrosis have gradually decreased and thus the long-term satisfaction rate has been raised up to 98% for palmar hyperhidrosis, 92% for craniofacial hyperhidrosis and 89% for axillary hyperhidrosis. The recurrent cases (14/1167) were treated successfully with reoperations of thoracoscopic sympathetic surgery. The optimal goal of therapy could be achieved by complete elimination of the hyperhidrotic symptom, by decreasing the incidence and degree of compensatory hyperhidrosis through a selective and limited resection, and by adopting the least invasive procedures. Sympathicotomy has provided the advantages of a limited extent of denervation and the resultant decrease of compensatory hyperhidrosis compared to sympathectomy. The reversible method of clipping may be an effective, provisionary means for cases of severe, intractable compensatory sweating. For craniofacial hyperhidrosis, T2 sympathicotomy or clipping has been proven to be superior to the T1 sympathectomy due to the decreased occurrence of Horner's syndrome and T3,4 sympathicotomy providing a satisfactory outcome with less compensatory hyperhidrosis for axillary hyperhidrosis.

Adolescent↗
PubMed1998

Cytotoxicity of heat-treated Korean mistletoe.

The cytotoxic effects of preparations of Korean mistletoe (Viscum album L. var. coloratum Ohwi) on non-tumorigenic A31 cells and tumorigenic MSV cells were investigated. While the aqueous extract from Korean mistletoe (<8 microg/ml) showed strong cytotoxicity on both cell lines, the heat-treated extract was much less cytotoxic with TD50 values of above 300 microg/ml. The heat-treated extract showed a growth-enhancing effect on non-tumorigenic cells and a cytotoxic effect on tumorigenic cells. The alkaloids fraction, which was isolated from the crude extract, was not cytotoxic to non-tumorigenic A31 cells up to 550 microg/ml, but was cytotoxic to tumorigenic MSV cells at 138 microg/ml. Heat treatment did not change the cytotoxic effects of the alkaloids fraction, indicating that the selective cytotoxicity of the heat-treated mistletoe extract on tumorigenic MSV cells might be due to its alkaloids. In order to study the changes in the cytotoxicity of fermented Korean mistletoe, the crude and heat-treated extracts were inoculated with Lactobacillus plantarum. During 7 days of fermentation, the cytotoxicity of the fermented heat-treated extract was increased while that of the fermented crude extract was not changed significantly.

Alkaloids↗