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S S Yoon

Publications and source records attributed to S S Yoon.

56 records · Page 4Linked to original sources

Multifocal hypointense cerebral lesions on gradient-echo MR are associated with chronic hypertension.

PURPOSE: To investigate the basis for multifocal hypointense lesions within the brain as identified on T2*-weighted gradient-echo MR imaging in patients with no known or presumed cause of these lesions. METHODS: In the first of a two-part study design, we retrospectively reviewed a case series of 38 patients whose gradient-echo MR images showed multiple hypointense lesions within the brain parenchyma. Thirty-one cases in which the cause was known or presumed (eg, head trauma or cavernous angioma) were excluded from further review. The MR studies and clinical findings of the remaining seven cases were reexamined. In the second part, using a cohort study design with respect to hypertension, we prospectively reviewed the gradient-echo images from MR studies of 65 patients and control subjects enrolled in two ongoing clinical studies, one on "possible vascular dementia" (n = 33) and the other on "possible motor neuron disorder" (n = 32). RESULTS: In the first part of the study, we found seven cases with a pattern of multiple hypointense lesions involving the deep gray matter nuclei, especially the basal ganglia (n = 6) and thalamus (n = 5). In addition, involvement of the corona radiata (n = 5), brain stem (n = 4), and cerebellum (n = 3) was seen. Clinical review revealed a history of chronic hypertension in all seven patients. In the cohort study, we found three of 65 persons who had two or more focal hypointense lesions that involved the basal ganglia or thalami. Review of the clinical data showed that all three patients were being treated for hypertension; also, all three were patients from the "possible vascular dementia" group. CONCLUSIONS: The MR imaging pattern of multifocal hypointense lesions within the basal ganglia, thalamus, and other deep cerebral structures is more commonly found among patients with a history of chronic hypertension than in patients without chronic hypertension.

Adult↗

Differential effects and transport kinetics of ascorbate derivatives in leukemic cell lines.

In order to investigate the differential effects of ascorbate derivatives on leukemic cell growth, we examined their stabilities and transmembrane transport efficiencies. The growth of HL-60 and U937 cells was dose-dependently inhibited by ascorbic acid and sodium ascorbate, but not by dehydroascorbic acid and magnesium ascorbyl 2-phosphate up to 200 microM. The growth-suppression by ascorbic acid was dependent on its redox state, showing a complete or partial reversion by ascorbate oxidase or FeCl3 addition, respectively. Three different patterns of intracellular ascorbic acid accumulation were observed by HPLC according to the species of ascorbate derivative applied for the incubation. Compared with the reduced form of ascorbic acid, the oxidized forms (dehydroascorbic acid, ascorbic acid plus ascorbate oxidase or FeCl3) were rapidly transported into cells and readily degraded, while magnesium ascorbyl 2-phosphate, a stable derivative of ascorbic acid, slowly elevated the intracellular level of ascorbic acid, reaching a plateau at 24 hours. We also measured the differential kinetics of ascorbic acid levels In culture supernatants following the addition of ascorbate derivatives. Ascorbic acid at 40, 10, or 1 microM was observed 3 hours following treatment with 100 microM of ascorbic acid, ascorbic acid plus FeCl3, or magnesium ascorbyl 2-phosphate, respectively. No ascorbic acid was found in the culture supernatant treated with dehydroascorbic acid. This order of ascorbic acid concentrations in culture supernatant reflects their growth-inhibitory effects. Thus the growth inhibitory effect of ascorbic acid appears to be dependent on its concentration in culture medium rather than its intracellular concentration. In conclusion, the results in this study indicate that the differential effects of ascorbate derivatives appear to be due to the actual concentration differences of the reduced form of ascorbic acid in culture medium following their addition, which is determined by their stability and efficiency of cellular uptake.

Ascorbate Oxidase↗