Biomedical subjects

Y Lee

Publications and source records attributed to Y Lee.

At least 19 recordsLinked to original sources

PubMed2001

Synergistic activation of RSK correlates with c-fos induction in MO7e cells stimulated with GM-CSF plus Steel factor.

Steel factor (SLF) plus GM-CSF induces proliferative synergy in factor-dependent cell line MO7e and hematopoietic progenitor cells. We previously reported ERK1/2 involvement in this synergy, but its downstream signaling molecules are not defined. Here, we investigated activation of the 90-kDa ribosomal S6 kinase (RSK) proteins by measuring the phosphorylation status and in vitro kinase activity in MO7e cells. Both GM-CSF and SLF induced activation of RSK, and the combined stimulation with these two cytokines induced synergistic and persistent activation of RSK. RSK activity was reduced by PI3 kinase inhibitor LY294002 or MEK1 inhibitor PD98059, suggesting that the ERK as well as the PI3 kinase pathways are involved in regulation of RSK activity. Sensitivities of RSK activity to inhibitory drugs correlated well with those of c-fos gene induction. Taken together, synergistic activation of RSK may contribute, at least in part, to the synergistic induction of c-fos after combined stimulation with GM-CSF plus SLF.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed2001

The interphase microtubule damage checkpoint defines an S-phase commitment point and does not require p21(waf-1).

Cell cycle checkpoints ensure orderly progression of events during cell division. A microtubule damage (MTD)-induced checkpoint has been described in G(1) phase of the cell cycle (G(1)MTC) for which little is known. The present study shows that the G(1)MTC is intact in activated T lymphocytes from mice with the p21(waf-1) gene deleted. However, p21(waf-1) gene deletion does affect the ratio of cells that arrest at the G(1)MTC and the spindle checkpoint after MTD. The G(1)MTC arrests T lymphocytes in G(1) prior to cdc2 up-regulation and prior to G(1) arrest by p21(waf-1). Once cells have progressed past the G(1)MTC, they are committed to chromosome replication and metaphase progression, even with extreme MTD. The G(1)MTC is also present in a human myeloid cell line deficient in p21(waf-1) gene expression. The p21-independent G(1)MTC may be important in cellular responses to MTD such as those induced by drugs used to treat cancer.

Animals↗

PubMed2001

Transcriptional and ERK1/2-dependent synergistic upregulation of p21(cip1/waf1) associated with steel factor synergy in MO7e.

Steel factor (SLF) plus GM-CSF induces proliferative synergy in myeloid progenitors and factor-dependent cell line MO7e. We previously reported that the protein level of cyclin-dependent kinase inhibitor p21(cip1/waf1) (p21) increased synergistically when MO7e cells were stimulated with SLF plus GM-CSF and that p21 induction was required for SLF synergistic responses. Here we show that this p21 induction is regulated at the transcriptional level. Based on use of a multiprobe RNase protection assay, the synergistic increase of p21 mRNA was unique among many cell cycle regulators. While STAT5A and 5B were activated after stimulation with GM-CSF alone or SLF plus GM-CSF, there was no difference in activation between the groups. p44/42 MAP kinase (ERK1/2) was synergistically activated by SLF plus GM-CSF, but SAPK/JNK and p38 MAP kinase were not. Synergistic induction of p21 was significantly decreased with a MEK1 inhibitor, suggesting that the ERK1/2 pathway is involved in the synergistic increase of p21 after GM-CSF plus SLF stimulation.

Cell Cycle↗

PubMed2001

Catalytic turnover of substrate benzylamines by the quinone-dependent plasma amine oxidase leads to H2O2-dependent inactivation: evidence for generation of a cofactor-derived benzoxazole.

Incubation of bovine plasma amine oxidase (BPAO) with benzylamine and various p-substituted analogues results in a time-dependent inactivation that is attributable to buildup of the H(2)O(2)-turnover product on the basis of protection afforded by coincubation with catalase. The mechanism of inactivation is distinct from that effected by H(2)O(2) itself, which requires higher concentrations. Solution studies using models for the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor reveal a loss of catalytic activity arising from oxidation of the dihydrobenzoxazole tautomer of the product Schiff base, that competes with hydrolytic release of benzaldehyde product. The resulting stable benzoxazole exhibits a characteristic absorption depending on the nature of the benzylamine p-substituent. For benzylamine itself, the model benzoxazole absorbs at 313 nm, in an area of strong absorption by the enzyme, whereas for 4-nitrobenzylamine, the absorption of the model benzoxazole is sufficiently red-shifted (at 365 nm) to be discerned above the background enzyme absorption. Inactivation of BPAO by 4-nitrobenzylamine is accompanied by loss of the resting TPQ anion absorption at 480 nm concomitant with generation of a new absorption near 360 nm. Resonance Raman spectra of the inactivated enzyme show a close correspondence with those for the model 4-nitrobenzylamine-derived benzoxazole. Substrate-dependent inactivation is also observed for the other two mammalian enzymes examined, equine plasma amine oxidase and human kidney amine oxidase. Catalase provides complete protection in these instances as well. Benzoxazole formation may constitute a common mechanism of inactivation of quinone-dependent amine oxidases by normal substrates in vitro if the product H(2)O(2) is permitted to accumulate. More importantly, the results suggest that the benzoxazole inactivation pathway may be important physiologically and may have influenced the distribution of amine oxidases and catalase in cells.

Amine Oxidase (Copper-Containing)↗

PubMed2001

High-dose therapy and autologous hematopoietic cell transplantation in children with primary refractory and relapsed Hodgkin's disease: atopy predicts idiopathic diffuse lung injury syndromes.

The use of high-dose therapy (HDT) and autologous hematopoietic cell transplantation (AHCT) for children and adolescents with primary refractory and relapsed Hodgkin's disease is increasing. The purpose of this retrospective analysis was to: (1) evaluate the outcome of HDT and AHCT in pediatric patients with Hodgkin's disease, and (2) identify factors that predispose patients to the development of transplantation-related complications. We describe the experiences of 34 pediatric patients from a single institution with primary refractory or relapsed Hodgkin's disease. HDT regimens consisted of cyclophosphamide and etoposide combined with either carmustine, chloroethylcyclohexylnitrosurea, or fractionated total body irradiation. Kaplan-Meier survival predicts that 67% (95% confidence interval [CI] 47%-87%) of patients will be alive and disease-free at 5 years. Nine patients had disease recurrence, of whom 5 relapsed after 1 year (1.5-6.3 years). Five patients succumbed to treatment-related toxicities, of whom 4 died of pulmonary failure. Fifteen patients (44%) developed post-AHCT idiopathic diffuse lung injury syndrome: acute alveolitis (n = 2); diffuse alveolar hemorrhage (n = 2); acute respiratory distress syndrome (n = 2); delayed interstitial pneumonitis (n = 8); and bronchiolitis obliterans (n = 1). The following factors did not predict for the development of a diffuse lung injury syndrome in univariate analysis: prior treatment with bleomycin, pre-HDT pulmonary function tests, and prior thoracic irradiation. Of the patients in our cohort, 44% had a history of atopy (allergic rhinitis and/or asthma). Multivariate logistic analysis revealed that a preexisting history of atopy was highly predictive of idiopathic pulmonary complications (P = .0001, odds ratio = 21, CI 3.6-125). Our experience shows that HDT followed by AHCT results in durable remissions in two thirds of pediatric patients with refractory and relapsed Hodgkin's disease, and a history of atopy is associated with post-AHCT pulmonary complications.

Adolescent↗

PubMed2001

The role of leptin resistance in the lipid abnormalities of aging.

Leptin resistance has been implicated in the pathogenesis of obesity-related complications involving abnormalities of lipid metabolism that resemble those of old age. To determine whether development of leptin resistance in advancing age might account for such abnormalities, we compared the effects of hyperleptinemia (>40 ng/ml) induced in 2-month-old and 18-month-old lean wild-type (+/+) Zucker diabetic fatty rats by adenovirus gene transfer. The decline in food intake, body weight, and body fat in old rats was only 25%, 50%, and 16%, respectively, of the young rats. Whereas in young rats plasma free fatty acids fell 44% and triacylglycerol (TG) 94%, neither changed in the rats. In hyperleptinemic young rats, adipocyte expression of preadipocyte factor 1 increased dramatically and leptin mRNA virtually disappeared; there was increased expression of acyl CoA oxidase, carnitine palmitoyl transferase 1, and their transcription factor peroxisome proliferator-activated receptor alpha, accounting for the reduction in body fat. These hyperleptinemia-induced changes were profoundly reduced in the old rats. On a high-fat diet, old rats consumed 28% more calories than the young and gained 1.5x as much fat, despite greater endogenous hyperleptinemia. Expression of a candidate leptin resistance factor, suppressor of cytokine signaling 3 (SOCS-3), was compared in the hypothalamus and white adipocytes of young and old rats before and after induction of hyperleptinemia; hypothalamic SOCS-3 mRNA was approximately 3x higher in old rats before, whereas it was 3x higher in WAT after, hyperleptinemia. We conclude that the anorexic and antilipopenic actions of leptin decline with age, possibly through increased SOCS-3 expression, and that this could account for the associated abnormalities in lipid metabolism of the elderly.

Acyl-CoA Oxidase↗

PubMed2001

Absence of direct antioxidant effects from volatile anesthetics in primary mixed neuronal-glial cultures.

BACKGROUND: Volatile anesthetics decrease ischemic brain injury. Mechanisms for this protection remain under investigation. The authors hypothesized that volatile anesthetics serve as antioxidants in a neuronal-glial cell culture system. METHODS: Primary cortical neuronal-glial cultures were prepared from fetal rat brain. Cultures were exposed to iron, H2O2, or xanthine-xanthine oxidase for 30 min in serum-free media containing dissolved isoflurane (0-3.2 mm), sevoflurane (0-3.6 mm), halothane (0-4.1 mm), n-hexanol, or known antioxidants. Cell damage was assessed by release of lactate dehydrogenase (LDH) and trypan blue exclusion 24 h later. Lipid peroxidation was measured by the production of thiobarbituric acid-reactive substances in a cell-free lipid system. Iron and calcium uptake and mitochondrial depolarization were measured after exposure to iron in the presence or absence of isoflurane. RESULTS: Deferoxamine reduced LDH release caused by H2O2 or xanthine-xanthine oxidase, but the volatile anesthetics had no effect. Iron-induced LDH release was prevented by the volatile anesthetics (maximum effect for halothane = 1.2 mm, isoflurane = 1.2 mm, and sevoflurane = 2.1 mm aqueous phase). When corrected for lipid solubility, the three volatile anesthetics were equipotent against iron-induced LDH release. In the cell-free system, there was no effect of the anesthetics on thiobarbituric acid-reactive substance formation in contrast to Trolox, which provided complete inhibition. Isoflurane (1.2 mm) reduced mean iron uptake by 46% and inhibited mitochondrial depolarization but had no effect on calcium uptake. CONCLUSIONS: Volatile anesthetics reduced cell death induced by oxidative stress only in the context of iron challenge. The likely reason for protection against iron toxicity is inhibition of iron uptake and therefore indirect reduction of subsequent intracellular oxidative stress caused by this challenge. These data argue against a primary antioxidant effect of volatile anesthetics.

Anesthetics, Inhalation↗

PubMed2001

A new surgical treatment of keloid: keloid core excision.

Keloids and hypertrophic scars result from excessive collagen deposition, the cause of which is not yet known. Unlike hypertrophic scars, keloids frequently persist at the site of injury, often recur after excision and always overgrow the boundaries of the original wound. There have been many trials to control keloids, but most of them have been unsuccessful. The authors propose a new surgical technique to treat keloids and name it keloid core extirpation. They excise the inner fibrous core from the keloid and cover the defect with a keloid rind flap, which is arterialized by the subcapsular vascular plexus. The authors treated 24 keloids of the ear, trunk, face, and genitalia with keloid core excision. Four cases of partial rind flap congestion or necrosis occurred. Those patients who healed primarily after surgery showed no evidence of keloid recurrence as long as they were followed. The authors have found the keloid core extirpation technique to be excellent in preventing keloid recurrence, with no adjuvant therapy after surgery.

Abdomen↗

PubMed2001

Correction of sunken and/or multiply folded upper eyelid by fascia-fat graft.

Sunken and/or multiply folded upper eyelid is one of the common, troublesome complications that can occur after Oriental blepharoplasty. In addition to orbital volume depletion, the traumatic surgical procedure of excessive fat removal might result in a varying degree of adhesion and injury to the orbital septum. Adhesiotomy followed by a restoration of volume is generally believed to be the logical way to correct such deformity. To restore volume and prevent re-adhesion, local tissues of the upper eyelid, free-fat graft, and dermis-fat graft have been used. However, local tissues are usually insufficient because of previous surgery, and the survival rate of grafted fat is often unpredictable. Moreover, the heaviness of the dermis-fat composite makes it a less than satisfactory choice. The authors value the use of free fascia-fat composite grafts for the treatment of such disfigurements. The fascia-fat composite is expected to have a better survival rate than free fat alone and to be lighter than a dermis-fat composite. In addition, the fascia-fat composite is abundant throughout the body and provides anatomical structure more similar to that of the repair site, namely, the damaged orbital septum and fat. The authors prefer the mons pubis, preauricular, and temporal areas for the donor site depending on the status of the damage. They treated 13 patients with sunken and/or multiply folded upper eyelids by fascia-fat composite grafts and obtained satisfactory results.

Adipose Tissue↗

PubMed2000

Slow recovery of body fat lost during adenovirus-induced hyperleptinemia.

In normal rats, adenovirus-induced hyperleptinemia causes disappearance of visible body fat, downregulation of lipogenic enzymes, and upregulation of oxidative enzymes and thermogenic proteins. In addition, preadipocyte markers replace mature adipocyte markers, suggesting dedifferentiation. In weight loss induced by caloric restriction, by contrast, the lipogenic machinery is essentially intact. To determine if the radical changes induced by leptin would slow the reappearance of body fat, we compared normal lean rats made hyperleptinemic by infusing an adenovirus-leptin construct with diet-matched littermates. Initially, in plasma leptin the hyperleptinemic rats averaged approximately 50x the controls and, although it declined progressively, it was still slightly elevated at 150 days (P < 0.05). In the hyperleptinemics, body fat mass, quantified by magnetic resonance spectroscopy, remained below the pretreatment value for 60 days, while in diet-matched controls it exceeded the pretreatment value. Epididymal fat pad weight in hyperleptinemics was still 28% below paired controls at 150 days posttreatment. Histologic examination revealed adipocytes of hyperleptinemic animals to be smaller 60 days after treatment. At 60 days, adipose tissue UCP-2 gene expression in hyperleptinemics was still above controls, but expression of other lipogenic and oxidative enzymes had returned to baseline expression levels. We conclude that in normal rats recovery of body fat following adenovirus-induced hyperleptinemia is much slower than after caloric restriction, possibly because of persistent upregulation of adipocyte UCP-2.

Adenoviridae↗

PubMed2000

An intronless gene encoding a poly(A) polymerase is specifically expressed in testis.

Previous work demonstrated that a single pre-mRNA could generate multiple forms of mammalian poly(A) polymerase mRNAs by alternative splicing or alternative polyadenylation. A cDNA encoding a testis-specific poly(A) polymerase was isolated in this study. The transcription level of Papt in testis of a 2 weeks old mouse was much lower than that of the general poly(A) polymerase gene, Pap. However, the transcription ratio of Papt to Pap was reversed in testis of a 4 weeks old mouse. Transient expression analysis showed that GFP-Papt fusion protein is present both in the nucleus and cytoplasm of HeLa cells. These results suggest that Papt is involved in polyadenylation of transcripts expressed during spermatogenesis.

Alternative Splicing↗

PubMed2000

1H-pyrazole-1-carboxamidines: new inhibitors of nitric oxide synthase.

1H-Pyrazole-1-carboxamidines were prepared as potential inhibitors of the three isozymes of nitric oxide synthase. All of the compounds were found to be competitive inhibitors of all three isoforms. The most selective compound prepared was 1H-pyrazole-N-(3-aminomethylanilino)-1-carboxamidine (14), which is 100-fold selective for nNOS over eNOS with a Ki value of 2 microM.

Amidines↗

PubMed2000

Liporegulation in diet-induced obesity. The antisteatotic role of hyperleptinemia.

To test the hypothesis that the physiologic liporegulatory role of hyperleptinemia is to prevent steatosis during caloric excess, we induced obesity by feeding normal Harlan Sprague-Dawley rats a 60% fat diet. Hyperleptinemia began within 24 h and increased progressively to 26 ng/ml after 10 weeks, correlating with an approximately 150-fold increase in body fat (r = 0.91, p < 0.0001). During this time, the triacylglycerol (TG) content of nonadipose tissues rose only 1-2.7-fold implying antisteatotic activity. In rodents without leptin action (fa/fa rats and ob/ob and db/db mice) receiving a 6% fat diet, nonadipose tissue TG was 4-100 times normal. In normal rats on a 60% fat diet, peroxisome proliferator-activated receptor alpha protein and liver-carnitine palmitoyltransferase-1 (l-CPT-1) mRNA increased in liver. In their pancreatic islets, fatty-acid oxidation increased 30% without detectable increase in the expression of peroxisome proliferator-activated receptor-alpha or oxidative enzymes, whereas lipogenesis from [14C]glucose was slightly below that of the 4% fat-fed rats (p < 0.05). Tissue-specific overexpression of wild-type leptin receptors in the livers of fa/fa rats, in which marked steatosis is uniformly present, reduced TG accumulation in liver but nowhere else. We conclude that a physiologic role of the hyperleptinemia of caloric excess is to protect nonadipocytes from steatosis and lipotoxicity by preventing the up-regulation of lipogenesis and increasing fatty-acid oxidation.

Animals↗

PubMed2000

Rapid, high-yield, solid-phase synthesis of the antitumor antibiotic sansalvamide A using a side-chain-tethered phenylalanine building block.

A 10-step solid-phase synthesis of the cytotoxic depsipeptide sansalvamide A (1) has been accomplished in an overall yield of 67% with >95% purity employing polymer-bound phenylalanine building block 2. Both the N- and C-termini of 2 are extended followed by on-resin head-to-tail macrocyclization of the linear peptide in a high yield. This should be a general stategy for the synthesis of diverse libraries of cyclic peptides and depsipeptides that contain exclusively phenylalanine and other hydrophobic side chains.

Antibiotics, Antineoplastic↗

PubMed2000

High-frequency acoustics of 3He in aerogel

High-frequency ( approximately 15 MHz) acoustics were performed on 3He in 98% porous silica aerogel using an acoustic cavity technique. Measurements of the sound attenuation in the normal Fermi liquid and superfluid display behavior quite different from the bulk owing to strong elastic scattering of quasiparticles. The transition from first-to-zero sound is completely obscured with a quasiparticle mean-free path estimated to be in the range of 200-300 nm. No collective mode attenuation peak was observed at or below the superfluid transition.

Journal Article↗

PubMed2000

Genomic analysis and functional expression of canine dopamine D2 receptor.

Dopamine D2 receptor (DRD2) is one of the five dopamine receptors with seven transmembrane domains that are coupled to the G protein. We have cloned and characterized the genomic and cDNA sequences of the canine DRD2 gene, which are 12.7 and 2.7 kb in size, respectively. The genomic DNA is composed of seven exons and six introns, encoding a 443 amino acid protein with 95% amino acid identity to other mammalian D2 receptors. A length polymorphism was detected in intron 3 of the receptor gene. We also characterized alternatively spliced forms of DRD2 cDNAs, DRD2L and DRD2S. They showed a higher level of expression in midbrain and thalamus. The ratio between the long and short form is similar in RT-PCR reaction. In human and rodent, the same two spliced forms are known to be coupled to G(i)-type heterotrimeric GTP binding protein, thereby opening an inwardly rectifying potassium channel, GIRK1. When the canine DRD2L and DRD2S were heterologously expressed in Xenopus oocytes, both forms activated GIRK1 potassium channels through coupling with G(i) protein. This activation was dose-dependent, demonstrating its ligand specificity.

Amino Acid Sequence↗

PubMed2000

Defective neurogenesis resulting from DNA ligase IV deficiency requires Atm.

Ataxia telangiectasia results from mutations of ATM and is characterized by severe neurodegeneration and defective responses to DNA damage. Inactivation of certain DNA repair genes such as DNA ligase IV results in massive neuronal apoptosis and embryonic lethality in the mouse, indicating the occurrence of endogenously formed DNA double-strand breaks during nervous system development. Here we report that Atm is required for apoptosis in all areas of the DNA ligase IV-deficient developing nervous system. However, Atm deficiency failed to rescue deficits in immune differentiation in DNA ligase IV-null mice. These data indicate that ATM responds to endogenous DNA lesions and functions during development to eliminate neural cells that have incurred genomic damage. Therefore, ATM could be important for preventing accumulation of DNA-damaged cells in the nervous system that might eventually lead to the neurodegeneration observed in ataxia telangiectasia.

Animals↗

PubMed2000

Leptin resistance of adipocytes in obesity: role of suppressors of cytokine signaling.

Liver-derived hyperleptinemia induced in normal rats by adenovirus-induced gene transfer causes rapid disappearance of body fat, whereas the endogenous adipocyte-derived hyperleptinemia of obesity does not. Here we induce liver-derived hyperleptinemia in rats with adipocyte-derived hyperleptinemia of acquired obesity caused by ventromedial hypothalamus lesioning (VMH rats) or by feeding 60% fat (DIO rats). Liver-derived hyperleptinemia in obese rats caused only a 5-7% loss of body weight, compared to a 13% loss in normoleptinemic lean animals; but in actual grams of weight lost there was no significant difference between obese and lean groups, suggesting that a subset of cells remain leptin-sensitive in obesity. mRNA and protein of a putative leptin-resistance factor, suppressor of cytokine signaling (SOCS)-1 or -3, were both increased in white adipose tissues (WAT) of VMH and DIO rats. Since transgenic overexpression of SOCS-3 in islets reduced the lipopenic effect of leptin by 75%, we conclude that the increased expression of SOCS-1 and -3 in WAT of rats with acquired obesity could have blocked leptin's lipopenic action in the leptin-resistant WAT population.

Adenoviridae↗