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D Lee

Publications and source records attributed to D Lee.

At least 253 records · Page 14Linked to original sources
PubMed1998

Solution structures of the melanocyte-stimulating hormones by two-dimensional NMR spectroscopy and dynamical simulated-annealing calculations.

Melanocortins, which are involved in melanocyte pigmentation control and glucocorticoid stimulation, have functional roles in various physiological mechanisms and have been shown to participate in higher cortical functions. Recently, it has also been reported that melanocyte-stimulating hormone (MSH) and melanocortin 4 receptor (MC4R) are the key components of the hypothalamic response to obesity. The solution structures of both melanocyte-stimulating hormone alpha-MSH (Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2) and its analog alpha-MSH-ND (Ac-Ahx-Asp-His-DPhe-Arg-Trp-Lys-NH2) (Ahx, 2-aminohexanoic acid) have been determined by two-dimensional NMR spectroscopy and simulated-annealing calculations. The NMR data revealed that alpha-MSH forms a hairpin loop conformation which includes conserved message sequences, whereas alpha-MSH-ND prefers a type I beta-turn comprising residues of Asp2-His3-DPhe4-Arg5. Final simulated-annealing structures of both alpha-MSH-ND and alpha-MSH peptides converged with rmsd of 0.07 nm for alpha-MSH-ND and 0.1 nm for alpha-MSH between backbone atoms, respectively. This result will provide the structural bases of melanocortin functions as well as valuable information for structure-based drug design involving the regulation of obesity and feeding.

Amino Acid Sequence↗
PubMed1998

Anastrozole versus megestrol acetate in the treatment of postmenopausal women with advanced breast carcinoma: results of a survival update based on a combined analysis of data from two mature phase III trials. Arimidex Study Group.

BACKGROUND: This report presents the results of a survival update based on the combined data from two studies that compared the efficacy and tolerability of anastrozole (1 or 10 mg once daily), a selective, nonsteroidal aromatase inhibitor administered orally, and megestrol acetate (40 mg 4 times daily) in the treatment of postmenopausal women with advanced breast carcinoma whose disease had progressed after treatment with tamoxifen. METHODS: Two randomized, parallel-group, multicenter trials were conducted, involving a total of 764 patients. The two trials were identical in design; both were double blind for anastrozole and open label for megestrol acetate. Overview analyses were conducted with the intent of strengthening the interpretation of results from each trial. The median follow-up duration for this survival update was 31 months. RESULTS: At the clinical dose of 1 mg daily, anastrozole demonstrated a statistically significant survival advantage over megestrol acetate, with a hazard ratio of 0.78 (P < 0.025)(0.60 < 97.5% confidence interval [CI] <1.0). The 1 mg anastrozole group also had a longer median time to death (26.7 months) compared with 22.5 months for the megestrol acetate group. The 10 mg anastrozole group also had a survival benefit over the megestrol acetate group, with a hazard ratio of 0.83 (P=0.09, not significant)(0.64 < 97.5% CI < 1.1). Higher 2-year survival rates were observed for both anastrozole treatment groups than for the megestrol acetate group (56.1%, 54.6%, and 46.3% for the groups given 1 mg anastrozole, 10 mg anastrozole, and megestrol acetate, respectively). CONCLUSIONS: This combined analysis of two trials of postmenopausal patients with advanced breast carcinoma has clearly demonstrated that, after disease progression with tamoxifen, treatment with anastrozole 1 mg once daily results in a statistically and clinically significant advantage over a standard treatment, megestrol acetate. This important benefit, in addition to the good tolerability profile of anastrozole, supports the use of this drug as a valuable new treatment option for this patient population.

Aged↗
PubMed1998

Hydrolysis of microcrystalline cellulose by cellobiohydrolase I and endoglucanase II from Trichoderma reesei: adsorption, sugar production pattern, and synergism of the enzymes.

Microcrystalline cellulose (10 g/L Avicel) was hydrolysed by two major cellulases, cellobiohydrolase I (CBH I) and endoglucanase II (EG II), of Trichoderma reesei. Two types of experiments were performed, and in both cases the enzymes were added alone and together, in equimolar mixtures. In time course studies the reaction time was varied between 3 min and 48 h at constant temperature (40 degrees C) and enzyme loading (0.16 micromol/g Avicel). In isotherm studies the enzyme loading was varied in the range of 0.08-2.56 micromol/g at 4 degrees C and 90 min. Adsorption of the enzymes and production of soluble sugars were followed by FPLC and HPLC, respectively. Adsorption started quickly (50% of maximum achieved after 3 min) but was not completed before 60-90 min. For CBH I a linear relationship was observed between the production of soluble sugars and adsorption, showing that the average activity of the bound CBH I molecules does not change with increasing saturation. For EG II the corresponding curve levelled off which is explained by initial hydrolysis of loose ends on Avicel. The enzymes competed for binding sites, binding of EG II was considerably affected by CBH I, especially at high concentration. CBH I produced more soluble sugars than EG II, except at conversions below 1%. At 40 degrees C when the enzymes were added together they produced 27-45% more soluble sugars than the sum of what they produced alone, i.e. synergistic action was observed (the final conversion after 48 h of hydrolysis was 3, 6, and 13% for EG II, CBH I, and their mixture, respectively). At 4 degrees C, on the other hand, when the conversion was below 2.5%, almost no synergism could be observed. Molar proportions of the produced sugars were rather stable for CBH I (11-15%, 82-89%, and <6% for glucose, cellobiose, and cellotriose, respectively), while it varied considerably with both time and enzyme concentration for EG II. The observed stable but high glucose to cellobiose ratio for CBH I indicates that the processivity for this enzyme is not perfect. EG II produced significant amounts of glucose, cellobiose, and cellotriose, which are not the expected products of a typical endoglucanase activity on a solid substrate. We explain this by hypothesizing that EG II may show processivity due to its extended substrate binding site and the presence of its cellulose binding domain.

Adsorption↗
PubMed1998

Transcriptional activation independent of TFIIH kinase and the RNA polymerase II mediator in vivo.

The carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II becomes multiply phosphorylated by protein kinases during early steps in the gene transcription cycle both in vivo and in vitro. In yeast, the major CTD kinase is a subunit of the general transcription factor TFIIH, and is encoded by an essential gene, KIN28. Although the CTD and its phosphorylation are important for transcription, in vitro studies have challenged whether CTD phosphorylation is an absolutely required step. The general importance of CTD phosphorylation by Kin28 for transcription in yeast has been suggested because, for all genes tested, transcription is inhibited at the non-permissive temperature in temperature-sensitive kin28 mutants. However, using such a mutant and a copper-inducible targeted destruction method, we show here that transcription of certain genes can be highly induced even when cells lack Kin28. We also show that transcription of these Kin28-independent genes is independent of Srb4 and Srb6, critical components of the CTD-associated transcriptional mediator complex. These results indicate that there are at least two distinct pathways for transcriptional activation: one is dependent on Kin28 and the mediator complex, and the other is not.

Animals↗
PubMed1998

Solution structure of a syndecan-4 cytoplasmic domain and its interaction with phosphatidylinositol 4,5-bisphosphate.

Syndecan-4, a transmembrane heparan sulfate proteoglycan, is a coreceptor with integrins in cell adhesion. It has been suggested to form a ternary signaling complex with protein kinase Calpha and phosphatidylinositol 4,5-bisphosphate (PIP2). Syndecans each have a unique, central, and variable (V) region in their cytoplasmic domains, and that of syndecan-4 is critical to its interaction with protein kinase C and PIP2. Two oligopeptides corresponding to the variable region (4V) and whole domain (4L) of syndecan-4 cytoplasmic domain were synthesized for nuclear magnetic resonance (NMR) studies. Data from NMR and circular dichroism indicate that the cytoplasmic domain undergoes a conformational transition and forms a symmetric dimer in the presence of phospholipid activator PIP2. The solution conformations of both free and PIP2-complexed 4V have been determined by two-dimensional NMR spectroscopy and dynamical simulated annealing calculations. The 4V peptide in the presence of PIP2 formed a compact dimer with two twisted strands packed parallel to each other and the exposed surface of the dimer consisted of highly charged and polar residues. The overall three-dimensional structure in solution exhibits a twisted clamp shape having a cavity in the center of dimeric interface. In addition, it has been observed that the syndecan-4V strongly interacts not only with fatty acyl groups but also the anionic head group of PIP2. These findings reveal that PIP2 promotes oligomerization of syndecan-4 cytoplasmic domain for transmembrane signaling and cell-matrix adhesion.

Amino Acid Sequence↗
PubMed1998

Transcription activation by Escherichia coli FNR protein: similarities to, and differences from, the CRP paradigm.

During transcription activation at FNR-dependent promoters where the DNA site for FNR overlaps the -35 element, a surface-exposed activating region in the upstream subunit of the FNR dimer interacts with the C-terminal domain of the RNA polymerase alpha subunit. Starting with a cloned fnr gene encoding a defective FNR derivative carrying substitutions in this activating region, we screened a library of random mutations to identify substitutions that restored FNR activity. Activity can be restored by substitutions at residues T118, E47 and K60. The locations of these residues identify three separate surface-exposed regions of FNR that can play a role in transcription activation. These three regions appear to be analogues of Activating Region 1, Activating Region 2 and Activating Region 3 of the cyclic AMP receptor protein, CRP: our results underscore the similarities between FNR and CRP.

Bacterial Proteins↗
PubMed1998

DLG3, the gene encoding human neuroendocrine Dlg (NE-Dlg), is located within the 1.8-Mb dystonia-parkinsonism region at Xq13.1.

Neuroendocrine-Dlg (NE-Dlg) is a member of the discs-large-related (DLG) subfamily of the membrane-associated guanylate kinase-related protein family. Based on evidence from model systems, this protein appears to be critical for synaptogenesis, acting as a site-specific organizational center for integral membrane proteins and their downstream signaling molecules associated with the cytoskeleton. NE-Dlg also directly interacts with the colorectal tumor suppressor adenomatous polyposis coli, suggesting that it may play a role in regulating cell proliferation in epithelial cells. To explore the genetic control of NE-Dlg, we developed a physical map of the chromosome region containing DLG3, the locus encoding NE-Dlg. Using human-hamster radiation hybrid mapping panels, we mapped DLG3 to Xq13.1 and established a sequence-tagged site marker map of the surrounding region. We then developed a yeast artificial chromosome (YAC) contig for this region. Encompassing approximately 2.0 Mb contained within five overlapping YACs, this contig also includes the dystonia-parkinsonism syndrome (DYT3) locus. The close proximity of DLG3 to the DYT3 region suggests that the gene encoding NE-Dlg is a candidate locus for this neurological disorder.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Variability and correlated noise in the discharge of neurons in motor and parietal areas of the primate cortex.

We analyzed the magnitude and interneuronal correlation of the variability in the activity of single neurons that were recorded simultaneously using a multielectrode array in the primary motor cortex and parietal areas 2/5 in rhesus monkeys. The animals were trained to move their arms in one of eight directions as instructed by a visual target. The relationship between variability (SD) and mean of the discharge rate was described by a power function with a similar exponent ( approximately 0.57), regardless of the cortical area or the behavioral condition. We examined whether the deviation from mean activity between target onset and the end of the movement was correlated on a trial-by-trial basis with variability in activity during the hold period before target onset. In both cortical areas, for about a quarter of the neurons, the neuronal noise of these two periods was positively correlated, whereas significant negative correlations were seldom observed. Overall, neurons with higher signal correlation (i.e., similar directional pattern) showed higher noise correlation in both cortical areas. On the other hand, when the data were divided according to the distance between the electrode tips from which the neurons were recorded, a consistent relationship between the signal and noise correlations was found only for pairs of neurons recorded through the same electrode. These results suggest that nearby neurons with similar directional tuning carry primarily redundant messages, whereas neurons in separate cortical columns perform more independent processing.

Action Potentials↗
PubMed1998

Effect of topical anti-inflammatory treatment on the long-term outcome of laser trabeculoplasty. Fluorometholone-Laser Trabeculoplasty Study Group.

PURPOSE: To investigate the effect of anti-inflammatory treatment on the long-term outcome of argon laser trabeculoplasty, we extended the short-term study of the Fluorometholone-Laser Trabeculoplasty Study Group. METHODS: Among the chronic open-angle glaucoma patients randomly assigned to the 0.25% fluorometholone or placebo eyedrops four times daily before and after argon laser trabeculoplasty in the Fluorometholone-Laser Trabeculoplasty Study, the long-term records of 27 patients (13 eyes in the fluorometholone group and 14 eyes in the placebo group) were available for our review and analysis. RESULTS: There were no statistically significant differences in the success rate of argon laser trabeculoplasty between the fluorometholone and control groups over the follow-up period of 4.6 +/- 3.4 years. CONCLUSION: While it decreased ocular inflammation and discomfort during the early postoperative period, peri-argon laser trabeculoplasty use of a topical corticosteroid did not influence the long-term intraocular pressure outcome of argon laser trabeculoplasty.

Administration, Topical↗
PubMed1998

Outcomes of primary phakic trabeculectomies without versus with 0.5- to 1-minute versus 3- to 5-minute mitomycin C.

PURPOSE: To compare the intraocular pressure and hypotony outcomes of primary phakic trabeculectomies with no mitomycin C (MMC), shorter MMC, and longer MMC exposure. METHODS: We evaluated primary phakic trabeculectomies with no MMC (36 eyes of 36 patients), 0.5- to 1-minute MMC (50 eyes of 50 patients), and 3- to 5-minute MMC (38 eyes of 38 patients) at the concentration of 0.5 mg/ml. Successful trabeculectomy was defined as an intraocular pressure of 21 mm Hg or less without development of a marked visual acuity loss associated with prolonged hypotony (intraocular pressure < 6 mm Hg over 3 months) and without the need for additional surgery to control intraocular pressure or treat postoperative complications. RESULTS: The three groups were similar in demographics, preoperative intraocular pressure, and medical dependency. However, the incidence of hypotony during the postoperative periods of 3 to 12 months was significantly higher in the 3- to 5-minute MMC group (P < .05, chi-square test). Severe visual acuity loss associated with hypotony was also more frequently found in the 3- to 5-minute MMC group than in the 0.5- to 1-minute (P = .009, chi-square test) group or the control group (P = .014, chi-square test). In addition, the success probabilities were significantly different among the three groups (P = .001, Kaplan-Meier survival analysis with log-rank test) and were the highest in the 0.5- to 1-minute MMC group and the lowest in the 3- to 5-minute MMC group. CONCLUSION: Shorter application (0.5 to 1 minute) of MMC appears to be optimal for the successful outcome of primary phakic trabeculectomy compared with no MMC or longer application of MMC at a concentration of 0.5 mg/ml.

Aged↗
PubMed1998

Changes, with age, in the phospholipid content of the intestinal mucus layer of the newborn rabbit.

BACKGROUND/PURPOSE: The high incidence of bacterial translocation in newborns is thought to be caused, in part, by the immaturity of the intestinal mucosal barrier. Recently, intestinal mucus phospholipids (PL) have been reported to be important factors in the function of this mucosal barrier. The aim of this study was to quantify changes, with age, in the intestinal mucus PL of the newborn rabbit. METHODS: Mucus was gently scraped from the small intestinal mucosal surface of rabbits of different ages (0, 7, 14, and 28 days old and adult; n = 6 for all groups). PL was extracted from the mucus and was separated by two-dimensional thin-layer chromatography. The isolated phospholipid spots were quantified for their phosphorus content. RESULTS: Total PL content of the mucus decreased significantly with age (day 0, 21+/-2; day 7, 16+/-4; day 14, 9+/-3; day 28, 2+/-1; adult, 1+/-1 micromol/g wet mucus; P = .0001). Phosphatidylcholine and phosphatidylethanolamine levels in the adult rabbits were significantly lower in comparison with the 0-, 7-, and 14-day-old pups (P < .05). In contrast, lysophosphatidylcholine and lysophosphatidylethanolamine were significantly higher in the 28-day-old and adult rabbits in comparison with the 0-, 7-, and 14-day-old pups (P < .05). Phosphatidylinositol + phosphatidylserine levels in 7-day-old rabbits was significantly higher compared with adult rabbits. There was no significant difference in the composition of sphingomyeline between groups. CONCLUSION: Significant changes in the content and composition of the intestinal mucus phospholipids were observed during the first month of life in rabbits.

Aging↗
PubMed1998

The effect of epidermal growth factor on bacterial translocation in newborn rabbits.

PURPOSE: Epidermal growth factor (EGF), which is present in breast milk, has both trophic and maturational effects on intestinal mucosa. The aim of this study is to determine the effect of EGF on spontaneous intestinal bacterial translocation (BT) in formula-fed newborn rabbits, who have a high incidence of BT compared with breast-fed newborn rabbits. METHODS: Sixty-one rabbit pups were divided into three groups: EGF(-), n=24, EGF(+), n=22, and breast-fed animals, n=15. Both the EGF(-) and EGF(+) groups were gavage fed a standard artificial formula three times daily. EGF was administered subcutaneously three times daily (1.5 microg/g body weight per day) in the EGF(+) group. The breast-fed group was fed by their mothers ad libitum. At 7 days of age, all rabbits were killed, and the mesenteric lymph nodes (MLN), liver, and spleen were cultured qualitatively for bacterial growth, while the cecum and ileum were quantitatively cultured. To determine the effect of EGF on mucus-producing cells, goblet cell numbers in the small intestine were quantified histologically. RESULTS: There was no BT to MLN, spleen, or liver in the breast-fed group. The incidence of BT to MLN and spleen was significantly lower in the EGF(+) compared with EGF(-) group; (EGF[+]: MLN, 45%; spleen, 32%; Liver, 27%; EGF[-]: MLN, 79%; Spleen 67%; Liver 29%; in EGF[+] MLN and Spleen P<.05 vEGF[-]). There was no significant difference in cecal and ileal bacterial colonization between the EGF(+) and EGF(-) groups. The number of goblet cells in the small intestine was significantly lower in the EGF(-) group compared with the EGF(+) group as follows: EGF(+), 14+/-3; EGF(-), 9+/-3; breast-fed, 11+/-5 goblet cells per 100 epithelial cell nuclei; P=.013. CONCLUSIONS: (1) EGF caused a significant decrease in spontaneous bacterial translocation in formula-fed newborn rabbits and was associated with an increase in the goblet cell number of the small intestine. (2) These changes occurred in spite of the fact that no changes in small bowel bacterial colonization were observed. (3) These results suggest, but do not prove, that EGF may provide protection for neonates from gut origin infection by improving the mucosal barrier function through increased goblet cell production, thus decreasing the incidence of spontaneous bacterial translocation in the newborn.

Animals↗