Seokjoon Lee

Stability of acetal and non acetal-type analogs of artemisinin in simulated stomach acid

A series of non acetal-type analogs of artemisinin containing C-C bond at position-12 have been found to be 15-22 times more stable than acetal(C-O)-type prodrugs of artemisinin in simulated stomach acid.

Recent Studies on Natural Products as Anti-HIV Agents

The discovery of medicinal agents capable of specifically inhibiting human immunodeficiency virus (HIV) is urgently needed due to its globally widespread infection. Most of clinically useful anti-HIV agents are nucleosides but their use is limited due to their severe toxicity and emerging drug resistance. More than 50% of world marketed drugs have their origin of the nature. Natural products, of which structural diversity is so broad, are good sources for the effective discovery of anti-HIV agents with decreased toxicity. Over the past decade, substantial progress has been made in research on the natural products for the anti-HIV agents. New natural products that have potent anti-HIV activities with novel structures were reviewed in this article. These compounds, isolated mainly from medicinal plants, in this review have been classified as secondary metabolites such as terpenes, phenolics, and naturally scarce peptides and sugars. Especially, terpenes and phenol substances have gained much interest due to their significant anti-HIV activities along with their structural diversity. Recent studies also showed that several polysaccharides are effective inhibitors of HIV replication. Most of chemotherapeutic targets reviewed in this article are found to be HIV reverse transcriptase (RT).

A concise synthesis and in vitro cytotoxicity of new labdane diterpenes

A new series of labdane-related diterpenes have been synthesized from (-)-sclareol and assayed in vitro cytotoxicity against mouse and human cancer cells. A key intermediate, homodrimane and furanolabdane derivatives show good in vitro cytotoxicity comparable to those of mitomycin C and adriamycin.

Valsalva retinopathy associated with fiberoptic gastroenteroscopy.

CASE REPORT A 45-year-old woman presented with a sudden loss of vision in her left eye, which occurred while she was having a routine upper fiberoptic gastroenteroscopy. According to the gastrointestinal specialist, the patient had performed multiple sustained Valsalva maneuvers during the procedure. Funduscopy showed a preretinal hemorrhage with a half disc diameter in the fovea of the left eye. COMMENTS A diagnosis of Valsalva retinopathy was made on the basis of history and fundus finding. The hemorrhage resolved within 2 months without any sequelae. To our knowledge, this is the first report of the occurrence of Valsalva retinopathy following a routine upper fiberoptic gastroenteroscopy.

Conversion of sclareol into (+)-galanolactone and (+)-labdienedial

Abstract A short, regiospecific and first synthesis of (+)-galanolactone 5 and (+)-labdienedial 11 was achieved from sclareol, respectively.

A case of photic retinal injury associated with exposure to plasma arc welding

Purpose To report of photic retinopathy induced by plasma arc welding, and the OCT (optical coherence tomography) results of damaged retinal lesions. Methods We describe a case report of a 37-year-old male, working in the steel industry, who presented with central scotoma in both eyes. Results On his first visit, one day after performing plasma arc welding with protective gear at work, his best corrected vision was 0.7 for both eyes. Ophthalmic examination of the fundus showed a round yellow lesion with an approximate size of 300 micrometers superonasal to the fovea of both eyes. On his next visit, one month later, his vision had recovered to 1.0, his symptoms had improved, and the ophthalmoscopic examination of the fundus revealed that the round yellow spots had disappeared from both eyes. Conclusions To our knowledge, this is the first report of photic retinopathy induced by plasma arc welding, and the OCT (optical coherence tomography) results of damaged retinal lesions have not previously been reported. For these reasons, we report this case.

A GPS sensing strategy for accurate and energy-efficient outdoor-to-indoor handover in seamless localization systems

Indoor localization systems typically locate users on their own local coordinates, while outdoor localization systems use global coordinates. To achieve seamless localization from outdoors to indoors, a handover technique that accurately provides a starting position to the indoor localization system is needed. However, existing schemes assume that a starting position is known a priori or uses a naive approach to consider the last location obtained from GPS as the handover point. In this paper, we propose an accurate handover scheme that monitors the signal-to-noise ratio SNR of the effective GPS satellites that are selected according to their altitude. We also propose an energy-efficient handover mechanism that reduces the GPS sampling interval gradually. Accuracy and energy efficiency are experimentally validated with the GPS logs obtained in real life.

Clinical Progress in Impending Central Retinal Vein Occlusion

Purpose Impending central retinal vein occlusion is associated with mild or no loss of vision; however, its progress and vision prognosis have not been clearly defined until now. Therefore, we studied the progress and prognoses in patients with impending central retinal vein occlusion. Methods For this study, we selected ten subjects who had been diagnosed with impending central retinal vein occlusion, and we retrospectively reviewed their progress and prognoses. Results The average age of the subjects was 31.0 years (18 to 48 years). Eight patients were male and two were female. The average observational period was 5.5 months. Six out of ten subjects were found to have no underlying systemic disease, four subjects had underlying disease. All ten patients were affected unilaterally. When initially tested, the affected eyes showed an average vision of LogMar 0.30. The final vision test revealed an average of LogMar 0.04, which indicates good progress and prognosis. In one patient, retinal hemorrhage and macular edema progressively worsened after the diagnosis, and the patient was treated with radial optic neurotomy. Conclusions The cases of impending central retinal vein occlusion that we observed seemed to primarily affect young patients with generally good prognoses. However, in some cases, the degrees of obstruction and hemorrhage increased as time progressed. This suggests that impending central retinal vein occlusion could develop into the prodromal phase of an acute attack.

Development of parafoveal exudates and serous retinal detachment in a pregnant woman with tuberous sclerosis.

The authors describe an unusual case of a serous detachment of the fovea and decreased vision with parafoveal exudates with subsequent spontaneous resolution and return of central vision in a pregnant patient with tuberous sclerosis. To our knowledge, this is the first report of an ocular change during gestation in a patient with tuberous sclerosis.