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Y S Ahn

Publications and source records attributed to Y S Ahn.

At least 19 recordsLinked to original sources
PubMed1992

Sequential changes in glycogen content, expression of glucose transporters and enzymic patterns during development of clear/acidophilic cell tumors in rat kidney.

Renal clear cell tubules and clear/acidophilic cell tumors were induced in male Sprague-Dawley rats by 7 weeks oral administration (stop model) of N-nitrosomorpholine (NNM) at a concentration of 12 mg/100 ml in the drinking water. Twelve, 23 and 34 weeks after withdrawal of NNM serial cryostat sections of the kidneys were histochemically analyzed for the following parameters: glucose transporter proteins (GLUT1, GLUT2), glycogen content and the activities of glycogen synthase (SYN), glycogen phosphorylase (PHO), glucose-6-phosphatase (G6Pase), glucose-6-phosphate dehydrogenase (G6PDH), hexokinase (HK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), pyruvate kinase (PK), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), alkaline phosphatase (ALP), acid phosphatase (ACP) and gamma-glutamyltransferase (GGT). Clear cell (glycogenotic) tubules first appeared at 23 weeks, and clear/acidophilic cell tumors at 34 weeks after withdrawal of the carcinogen. G6Pase, ALP, GGT and GLUT2 were absent in clear cell tubules, clear/acidophilic cell tubules, and clear/acidophilic cell tumors indicating a sequential origin of all these types of lesions from the collecting duct system, in line with previous morphological findings. In comparison to the collecting duct epithelium, glycogenotic tubules demonstrated an increased activity of PHO and reduced activities of glycolytic and mitochondrial enzymes, which were accompanied by a strongly reduced expression of GLUT1. Moderately increased activities of glycolytic and mitochondrial enzymes were observed in the clear cells of clear/acidophilic cell tubules and tumors compared with those in glycogenotic tubules. They had slightly increased activities of the glycolytic enzymes GAPDH and PK compared with normal collecting duct epithelium, while most of them were nearly lacking in GLUT1. Our findings suggest that glycogen storage is not due to an increased uptake of glucose from the blood, but results from a disturbance in intracellular flux of metabolites. The development of clear cell tubules from the normal collecting duct epithelium is accompanied by a markedly decreased expression of GLUT1 along with a reduction in glycolytic and mitochondrial enzymes. This reduction of enzyme activities is replaced by an increase in enzyme activities in clear/acidophilic cell tumors indicating a fundamental shift in carbohydrate metabolism during progression from preneoplastic to neoplastic lesions.

Animals↗
PubMed1992

Allotransplantation of rat islets into the cisterna magna of streptozotocin-induced diabetic rats.

Islets were isolated from the pancreata of Sprague-Dawley rats and transplanted into streptozotocin-induced diabetic outbred Wistar rats. The effect of transplantation of islets into the cisterna magna on the diabetic state of the recipients was compared with that of the conventional transplantation of islets into liver via the portal vein. After successful intraportal (IP) transplantation, rejection took place between days 7 and 15 in all diabetic recipients. All of the eleven rats surviving after stereotaxic implantation of islets into the cisterna magna returned to normoglycemia within 7 days after transplantation. Nine of the recipients with intra-cisterna magna (IM) islet allografts were still normoglycemic at 210 days after transplantation. The glucose disappearance rate of the IM transplant rats was slower than that of the IP transplant rats, and blood glucose returned to the normal basal level within 5 hr following glucose administration. Although the insulin levels were almost undetectable in cerebrospinal fluid before IM transplantation, the insulin levels were markedly increased after IM transplantation and twice as great in CSF than blood. Thus, these findings indicate that the cisterna magna can serve as an immunologically privileged site for implantation of allogeneic pancreatic islets, and islets in CSF can regulate and maintain normal glucose homeostasis via secretion of insulin across the blood-brain barrier.

Animals↗
PubMed1992

Clinical significance of platelet microparticles in autoimmune thrombocytopenias.

Platelet microparticles (PMPs) are vesicles derived from platelet membranes that are too small (less than 0.5 micron) to be detected in routine platelet counting. They arise in association with platelet activation and other unknown causes. Elevated PMPs have been observed in idiopathic thrombocytopenic purpura (ITP), a disorder in which autoantibody interacts with platelets and the opsonized platelets are destroyed by macrophages. However, the clinical significance of PMP has been unknown. Using flow cytometry, we examined PMP concentrations in 62 patients with ITP and in 33 normal control subjects to assess the clinical significance of PMP in ITP. When compared with PMP levels in control subjects, PMP levels were significantly higher (p less than 0.005) in patients with ITP, but considerable variation among individual patients was observed. Patients with platelet counts less than or equal to 60,000 were evaluated for correlation of PMP levels with manifestations of thrombocytopenias; patients without symptoms (free of petechiae or mucosal bleeding) are found to have significantly higher PMP levels (p less than 0.05) than patients with symptoms, suggesting hemostatic protection by PMP. Additionally, we identified a group of patients with ITP who experienced neurologic complications resembling transient cerebral ischemic attacks (TIAs): recurrent episodes of dizzy spells or weakness in mild cases, and coma, seizure, or progressive dementia in advanced cases. Small cerebral infarcts were demonstrated by computed axial tomography scan or magnetic resonance imaging in spite of severe thrombocytopenias. Patients with this syndrome are often found to have higher PMP levels (p less than 0.005) when compared with the group free of neurologic complications. It is concluded that PMPs play an important role in hemostasis in patients with thrombocytopenia, and that high concentrations of hemostatically active PMP can be thrombogenic in certain clinical settings. Quantitation and characterization of PMP is important in assessment and management of patients with thrombocytopenia.

Aged↗
PubMed1991

Danazol therapy for cyclic thrombocytopenia.

Cyclic thrombocytopenia is a rare disease characterized by cyclic oscillations of platelet counts from very low to normal or higher. Severe hemorrhage may occur during the thrombocytopenic phase. To date, treatments for this disorder have been disappointing. Its pathophysiology is unknown. We report a successful outcome using danazol therapy. Prior to danazol treatment, the patient had a 7 year history of cyclic thrombocytopenia, refractory to glucocorticoids, splenectomy, azathioprine, vinca alkaloids, plasma infusions, and hormonal manipulation with Premarin-Provera. Her platelet counts were found to be oscillating in a 21 day cycle between 1 x 10(9)/L and 500 x 10(9)/L. Platelet-associated antibodies were positive and chromium-labeled platelet survival time was shortened. Following 2 months of danazol therapy, her platelet counts at the nadirs were significantly higher than at previous nadirs, and at no time thereafter dropped to the critically low values seen before danazol. Also at 2 months of danazol treatment, the patient reported amelioration of petechiae, and at 9 months it was completely cleared. However, platelet-associated IgG remained positive and platelet counts continued to oscillate, typically between 100 x 10(9)/L and 300 x 10(9)/L in the second year, but stabilized at 3 years, when platelet-associated IgG also disappeared. Danazol was discontinued after 3.5 years. The patient remains in unmaintained remission today, approximately 5 years after discontinuance of danazol. It can be argued that the long-term outcome was due to spontaneous remission. However, significant improvement was noted from the outset of danazol therapy, and further improvement with long-term therapy, as seen in the response of chronic ITP to danazol therapy. Danazol may offer lasting benefit in cyclic thrombocytopenia.

Autoimmune Diseases↗
PubMed1990

Efficacy of danazol in hematologic disorders.

Danazol, an attenuated androgen developed for the treatment of endometriosis, has recently been found useful in the treatment of several hematologic disorders, including idiopathic thrombocytopenic purpura (ITP), autoimmune hemolytic anemia (AIHA), paroxysmal nocturnal hemoglobinuria, myelodysplastic syndrome, and others. Our studies of the past 6 years have demonstrated that danazol is advantageous in the treatment of AIHA, and in specifically defined populations of ITP patients. Of 96 ITP patients treated with danazol 61% overall had excellent/good responses, but this rate varied markedly with prognostic factors, e.g. 82% in older women versus only 18% in younger women. Of 28 AIHA patients, 77% with idiopathic type and 60% with secondary type were excellent/good responders. When the drug was discontinued after 1 year or more of therapy, lasting unmaintained remissions of up to 5 years were often observed in both ITP and AIHA, a notably important benefit. The side-effects of danazol are generally much less serious than with glucocorticoids. Glucocorticoids can be tapered off and in most cases discontinued completely with danazol therapy in AIHA and chronic ITP. Approximately one third of ITP patients who failed on glucocorticoids are successfully maintained on danazol. Its mechanism of action in these disorders is currently under study in our laboratory, stimulated by new findings. Tentatively, danazol appears to modify cell membranes in a manner leading to specific immune modulations, as discussed. Further study is warranted to explore its application to other autoimmune and membrane-related disorders, and to clarify its mechanism of therapy.

Adjuvants, Immunologic↗
PubMed1989

Long-term danazol therapy in autoimmune thrombocytopenia: unmaintained remission and age-dependent response in women.

STUDY OBJECTIVE: To assess the long-term benefit and side effects of danazol therapy, and to delineate factors influencing the responses in patients with autoimmune thrombocytopenia. DESIGN: Before and after trial. SETTING: Referral-based hematology clinics and the University of Miami teaching hospitals. PATIENTS: Data were collected on 96 patients (60 women and 36 men, 45 of whom had had splenectomies) receiving danazol therapy for autoimmune thrombocytopenia and analyzed. INTERVENTION: Danazol was added to the previous therapy or begun as an initial therapy. Glucocorticoids were tapered gradually. MEASUREMENTS AND MAIN RESULTS: The overall response rate to danazol was 61.4%. Among responders, the platelet counts (mean +/- SD) before and after danazol treatment were 36 +/- 24 x 10(9)/L and 145 +/- 77 x 10(9)/L, respectively, and the time to response was 2.7 +/- 3 months. Sex, age, and the status of the spleen (absent or present) influenced the responses to danazol. In women, but not in men, response rates improved with advancing age, especially in the nonsplenectomized women. This may be because estrogen levels are high in younger women and low in older women and men. Danazol, when given longer than a year, induced remissions lasting for years even after its discontinuation, but early relapses were frequent when danazol was administered for less than 6 months. Platelet-associated IgG returned to normal range during unmaintained remission. CONCLUSION: Danazol is best suited for long-term medical management of autoimmune thrombocytopenia. It is well tolerated, and lasting, unmaintained remissions often occur after prolonged danazol administration. Age, sex, and the status of the spleen influence the responses. When danazol therapy is used, glucocorticoids can be substantially reduced in dosage or withdrawn. Danazol is a good alternative to splenectomy in elderly persons, especially in women.

Adolescent↗
PubMed1989

Spontaneous remission of acute leukemia after the termination of pregnancy.

A 28-year-old woman in the third trimester of her pregnancy was found to have acute myelocytic leukemia. The baby was delivered by Cesarean section and her leukemia underwent spontaneous remission. However, 3 months later, she presented with massive painful leukemic infiltration of the breasts as initial manifestation of relapse, followed by systemic symptoms of leukemia. In vitro culture of the leukemic cells demonstrated characteristics of macrophage cell line. This case illustrates a unique sequence of events: spontaneous remission after the termination of pregnancy, which has profound hormonal alterations, and relapse in a very hormone-sensitive organ, the breast, a few months later when the hormonal milieu was resumed. This suggests hormonal dependence of her leukemic cells and potential for hormonal manipulation in a certain subset of human leukemia.

Adult↗
PubMed1989

Sex difference in the CD4 + CD45R+ T lymphocytes in normal individuals and its selective decrease in women with idiopathic thrombocytopenic purpura.

Chronic idiopathic thrombocytopenic purpura (ITP) is a well-defined autoimmune hematologic disorder. It is more common in women than men. We have shown that patients with active disease have abnormal T cell subsets which are more perturbed in women than in men and functional abnormalities that are confined to the T lymphocytes. In the current study, the anti-2H4 (CD45R) monoclonal antibody was used to divide the CD4 subset into their CD4+ CD45R+ and CD4+ CD45R- T lymphocytes. The subpopulations were measured in the peripheral blood of 26 women and 15 men with active ITP, 16 women and 8 men with disease in remission, and 33 normal healthy women and men. Normal women had increased percentages (P less than 0.0001) and numbers (P less than 0.005) of the CD4+ CD45R+ lymphocytes compared to normal men. Women with active disease had reduced percentages and numbers of CD4+ CD45R+ lymphocytes compared to normal women (P less than 0.0001) and women with disease in remission (P less than 0.001). Those women with decreased CD4+ CD45R+ lymphocytes had a significantly depressed lymphocyte response to polyclonal T cell mitogens. In contrast, men with active disease had neither such phenotypic changes nor functional correlations. The percentages and numbers of CD4+ CD45R- lymphocytes were not changed in either sex with active disease. In conclusion, women, but not men, with active ITP appear to possess a reduced subpopulation of CD4+ CD45R+ T lymphocytes.

Antibodies, Monoclonal↗
PubMed1989

Danazol therapy renders red cells resistant to osmotic lysis.

Danazol, an attenuated androgen, is useful in endometriosis, idiopathic thrombocytopenic purpura (ITP), and autoimmune hemolytic anemia (AIHA). However, its mechanism of action is unknown. We investigated the possibility that danazol affects cell membranes directly. Red cell osmotic fragility was studied in patients receiving danazol. A significant decrease in osmotic fragility was observed. Accompanying the change, peripheral blood smears showed many target cells and electron microscopy revealed extra folds in erythrocyte membranes. Twenty-two patients were studied prospectively before and after danazol. Osmotic fragility decreased significantly (P less than 0.001) in 1 month of therapy and progressed with further treatment. A rebound increase (P less than 0.01) was observed in 1 month after discontinuation of danazol among 16 patients. Incubation experiments showed that danazol-induced changes are not reversed with normal sera. Patient sera did not induce the changes in normal red cells. Danazol in vitro protected red cells from osmotic lysis at low concentrations but enhanced lysis at high concentrations. We suggest that danazol alters red cell membranes directly to increase their surface area, inducing target cell formation and increasing their resistance to osmotic lysis.

Danazol↗
PubMed1989

Very low dose danazol in idiopathic thrombocytopenic purpura and its role as an immune modulator.

Danazol, an attenuated androgen, has been used successfully at its conventional dose (400-800 mg/day) in the treatment of idiopathic thrombocytopenic purpura (ITP). To minimize side effects, the authors tried a very low dose (50 mg/day) regimen which has not been used in any other disease and observed its efficacy in ITP. Fifteen patients were given this dosage of danazol. Its effects on T-cell subsets, B cells, and blastogenic response to pokeweed mitogen (PWM) and staphylococcus aureus (Staph A) were studied before and during therapy. The percentage of CD3 and the percentage and numbers of CD4 were significantly increased during therapy. Responses to PWM, a T-cell dependent B cell mitogen, were also significantly elevated during therapy. However, no change in the percentage of B (CD19) lymphocytes and response to Staph A, a polyclonal B cell mitogen, were noted. There were seven excellent-good and eight fair-poor responses in platelet counts. The excellent-good responders were found to have a more stable CD4 subset between before and during therapy compared to the fair-poor responders (p less than 0.05, Fisher's exact test). Very low dose danazol regimen, therefore, produced a significant increase in the CD4 without affecting the B cells. However, the excellent-good responder patients showed no significant increase in the CD4 lymphocytes.

Adult↗
PubMed1988

Depressed functional and phenotypic properties of T but not B lymphocytes in idiopathic thrombocytopenic purpura.

Chronic idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder in which the abnormality in cellular immunity has remained only vaguely defined. Previously we have shown that patients with ITP in its active phase have abnormal T cell subsets. We then examined the phenotypes of T and B lymphocytes in an additional 28 patients with ITP and 32 age- and sex-matched normal controls and compared the lymphocytes' capacity to respond to polyclonal T, T cell-dependent B, and B cell mitogens. Blastogenesis to optimal (5.0 micrograms/mL) and suboptimal (0.5 microgram/mL) concentrations of the polyclonal T cell mitogens were markedly depressed in patients compared with normal controls (P less than .0005). Similarly, a severe depression in response was noted with the polyclonal T cell-dependent B cell mitogen (P less than .000001). No difference was seen, however, with the polyclonal B cell mitogen. The proportions of pan-T and T helper/inducer lymphocytes were significantly depressed (P less than .005 and P less than .000005 respectively), and the T suppressor/cytotoxic lymphocytes increased (P less than .02) in patients relative to controls. But there was no difference in the proportion of B lymphocytes or in their functional response. The abnormal cellular immunity appears to be due to a defect in the T lymphocyte population without involvement of the B lymphocytes.

Adult↗
PubMed1987

Increased platelet calcium in thrombosis and related disorders and its correction by nifedipine.

Using chlorotetracycline (CTC) as a probe we studied calcium homeostasis of platelets in various disorders. Studied were healthy subjects and patients with disorders where platelets play an important role. These included thromboses, hypertension, diabetes mellitus, vasculitis, immune thrombocytopenia, thrombotic thrombocytopenic purpura, myelofibrosis, hemolytic anemias and uremia. Significant elevation of calcium levels were observed in all of these disorders except uremia. Nifedipine reduced or normalized the increased levels in most patients and its discontinuation resulted in a return of the abnormality. We propose that platelets in thromboses and related disorders are exposed to subcritical concentrations of activating factors, leading to enhanced calcium influx and elevated free cytoplasmic calcium followed by elevated resting dense tubular calcium. Nifedipine appears to protect platelets from these stimuli and coupled with their known action on vessel walls, calcium channel blockers show promise as antiatherogenic as well as antithrombotic agents.

Arteriosclerosis↗
PubMed1987

Immune modulation by danazol in autoimmune thrombocytopenia.

Danazol, an attenuated androgen, has recently been introduced into the treatment of autoimmune thrombocytopenia. We studied its effects on T helper/inducer (Thi) and T suppressor/cytotoxic (Tsc) lymphocytes in these patients. Prospectively nine patients were studied with their T-cell subsets measured before and during danazol therapy. Increases in the percentage of Thi lymphocytes (P less than 0.05) and Thi/Tsc ratios (P less than 0.001) were observed at 1 and 3 months of treatment. Retrospectively T-cell subset data on 30 patients not treated with danazol and 36 patients on danazol were compared with those of 35 normal controls. The group not on danazol had lower percentages of Pan T (P less than 0.05), Thi (P less than 0.002), and Thi/Tsc ratios (P less than 0.00005), and had higher percentages of Tsc lymphocytes (P less than 0.01), than those of controls. In the group treated with danazol the percentages of Pan T, Thi, and Tsc lymphocytes were similar to those of controls. The percentage of Thi in the treated group was higher (P less than 0.002) than in the untreated group. Thus, danazol appears to be an effective immune modulator, correcting the abnormality of T-cell subsets seen in autoimmune thrombocytopenia by increasing the percentage of Thi lymphocytes.

Autoimmune Diseases↗
PubMed1987

Abnormal calcium handling by platelets in thrombotic disorders.

This study presents a quantitative comparison of the free cytoplasmic calcium concentration ([Ca2+]cyt) and the free concentration in the lumen of the dense tubules of the human platelet. The former was measured by the fluorescence of the high affinity indicator quin2 and latter by the fluorescence of chlorotetracycline (CTC). The CTC technique monitors calcium-CTC complex accumulation in the lumen of dense tubules and mitochondria when washed platelets were incubated in 2 mM Ca2+. Resting cytoplasmic and dense tubular Ca2+ concentrations were studied in platelets from patients suffering from venous and arterial thrombosis. Compared with normal controls (0.40 +/- 0.10, n = 54), the values of the calcium-CTC ratios were 0.68 +/- 0.19 (n = 16, p less than 0.005) in venous thrombosis; 0.75 +/- 0.18 (n = 14, p less than 0.005) in cardiovascular accident; 0.84 +/- 0.18 (n = 6, p less than 0.005) in occlusive peripheral vascular diseases; and 0.42 +/- 0.10 (n = 21, p greater than 0.1) in patient controls. The dense tubular Ca2+ levels for both patients and controls were perfectly correlated with the cytoplasmic levels using an equation that assumes that the dense tubular free calcium concentration ([Ca2+]dt) has a second power dependence on [Ca2+]cyt. The abnormal Ca2+ handling of platelets obtained from thrombotic patients could be completely reversed by preincubation with the calcium channel blocker verapamil. These observations suggest that the primary Ca2+ handling defect is the leakage through activated channels in the plasma membrane. The defect and the elevated resting [Ca2+]cyt and [Ca2+]dt are adequate to explain the observation of increased rates of collagen-activated aggregation in the above-mentioned group of patients. The results can be explained by platelets from thrombosis patients being exposed to activating factors in the circulation, resulting in Ca2+ channel activation. Channel activation persists through the process of platelet isolation and washing and is manifested in higher measured values of [Ca2+]cyt and [Ca2+]dt in the "resting state." This would bring the platelet closer to its aggregation when aggregation-inducing agents are added. The CTC test is shown to be a useful and convenient means of detecting this abnormality.

Blood Platelets↗
PubMed1987

Low-dose danazol therapy in idiopathic thrombocytopenic purpura.

Although danazol is effective in the treatment of idiopathic thrombocytopenic purpura, its long-term safety and optimal dosage are not well established. We compared low (50 mg/d) and conventional (400 to 800 mg/d) dosages in 24 patients. Thirteen patients received the low dose 1 to 24 months after conventional doses had been discontinued (group 1). Five patients received low doses immediately after the conventional doses (group 2). Six patients were treated with low doses from the outset (group 3). In group 1, similar responses to either dose were seen in 9 patients, whereas there were better responses to conventional doses in 3 and to the lower dose in 1. All patients in group 2 maintained remissions with low doses. There were two excellent-good responses, one fair, and three poor responses in group 3. Side effects were generally less frequent and severe with the low doses. Low-dose danazol is better tolerated but took longer to obtain remissions, and is useful for maintenance therapy in the management of idiopathic thrombocytopenic purpura.

Adolescent↗