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81.
82.
Diluk RW Kannangara Sheena N Ramasamy Praveen L Indraratna Sophie L Stocker Garry G Graham Graham Jones Ian Portek Kenneth M Williams Richard O Day 《Arthritis research & therapy》2012,14(4):R189
Introduction
Hyperuricemia is the greatest risk factor for gout and is caused by an overproduction and/or inefficient renal clearance of urate. The fractional renal clearance of urate (FCU, renal clearance of urate/renal clearance of creatinine) has been proposed as a tool to identify subjects who manifest inefficient clearance of urate. The aim of the present studies was to validate the measurement of FCU by using spot-urine samples as a reliable indicator of the efficiency of the kidney to remove urate and to explore its distribution in healthy subjects and gouty patients.Methods
Timed (spot, 2-hour, 4-hour, 6-hour, 12-hour, and 24-hour) urine collections were used to derive FCU in 12 healthy subjects. FCUs from spot-urine samples were then determined in 13 healthy subjects twice a day, repeated on 3 nonconsecutive days. The effect of allopurinol, probenecid, and the combination on FCU was explored in 11 healthy subjects. FCU was determined in 36 patients with gout being treated with allopurinol. The distribution of FCU was examined in 118 healthy subjects and compared with that from the 36 patients with gout.Results
No substantive or statistically significant differences were observed between the FCUs derived from spot and 24-hour urine collections. Coefficients of variation (CVs) were both 28%. No significant variation in the spot FCU was obtained either within or between days, with mean intrasubject CV of 16.4%. FCU increased with probenecid (P < 0.05), whereas allopurinol did not change the FCU in healthy or gouty subjects. FCUs of patients with gout were lower than the FCUs of healthy subjects (4.8% versus 6.9%; P < 0.0001).Conclusions
The present studies indicate that the spot-FCU is a convenient, valid, and reliable indicator of the efficiency of the kidney in removing urate from the blood and thus from tissues. Spot-FCU determinations may provide useful correlates in studies investigating molecular mechanisms underpinning the observed range of efficiencies of the kidneys in clearing urate from the blood.Trial Registration
ACTRN12611000743965 相似文献83.
Cell membrane-associated folate receptors are selectively overexpressed in certain human tumors. The high affinity of folic acid for folate receptors provides a unique opportunity to use folic acid as a targeting ligand to deliver chemotherapeutic agents to cancer cells. Folate-tethered liposomes bearing pteroyl-gamma-glutamate-cysteine-polyethylene glycol (PEG)-distearoylphosphatidylethanolamine (DSPE) as the targeting component are under investigation as mediators of drug and gene delivery to cancer cells that overexpress folate receptors. Pteroyl-gamma-glutamate-cysteine synthesis is one of the crucial starting steps in the preparation of pteroyl-gamma-glutamate-cysteine-PEG-DSPE. However, published methods for the synthesis of pteroyl-gamma-glutamate-cysteine provide low yields and are not easily reproducible. Therefore, we developed a modified synthetic method for the removal of the N(10)-trifluoroacetyl group after cleavage/deprotection that is reliable, is easily reproducible, and has high yield (38%) compared with an unreliable yield of 3-20% with the earlier methods. Folate-tethered liposomes containing calcein or doxorubicin were prepared using pteroyl-gamma-glutamate-cysteine-PEG-DSPE as the targeting component along with nontargeted liposomes with PEG-DSPE. The results of the uptake of calcein and cytotoxicity of doxorubicin in human cervical cancer HeLa-IU(1) cells and human colon cancer Caco-2 cells demonstrated that folate-tethered liposomes were efficient in selective delivery to cancer cells overexpressing folate receptors. The improvement in yield of the targeting component can significantly facilitate "scale up" of folate receptor-mediated liposomal cancer therapy to the preclinical and clinical levels of investigations. 相似文献
84.
Varga EV Yamamura HI Rubenzik MK Stropova D Navratilova E Roeske WR 《Life sciences》2003,74(2-3):299-311
Opioid receptor agonists mediate their analgesic effects by interacting with Gi/o protein-coupled opioid receptors. Acute treatment with opioid agonists is thought to mediate analgesia by hyperpolarization of presynatic neurons, leading to the inhibition of excitatory (pain) neurotransmitters release. After chronic treatment however, the opioid receptors gradually become less responsive to agonists, and increased drug doses become necessary to maintain the therapeutic effect (tolerance). Analgesic tolerance is the result of two, partially overlapping processes: a gradual loss of inhibitory opioid function is accompanied by an increase in excitatory signaling. Recent data indicate that chronic opioid agonist treatment simultaneously desensitizes the inhibitory-, and augments the stimulatory effects of the opioids. In the present paper we review the molecular mechanisms that may have a role in the augmentation of the excitatory signaling upon chronic opioid agonist treatment. We also briefly review our recent experimental data on the molecular mechanism of chronic opioid agonist-mediated functional sensitization of forskolin-stimulated cAMP formation, in a recombinant Chinese hamster ovary cell line stably expressing the human delta-opioid receptor (hDOR/CHO). To interpret the experimental data, we propose that chronic hDOR activaton leads to activation of multiple redundant signaling pathways that converge to activate the protein kinase, Raf-1. Raf-1 in turn phosphorylates and sensitizes the native adenylyl cyclase VI isoenzyme in hDOR/CHO cells, causing a rebound increase in forskolin-stimulated cAMP formation upon agonist withdrawal. 相似文献
85.
Background
As the use of microarray technology becomes more prevalent it is not unusual to find several laboratories employing the same microarray technology to identify genes related to the same condition in the same species. Although the experimental specifics are similar, typically a different list of statistically significant genes result from each data analysis. 相似文献86.
Phylogenetic utility of elongation factor-1 alpha in noctuoidea (Insecta: Lepidoptera): the limits of synonymous substitution 总被引:2,自引:1,他引:1
Mitchell A; Cho S; Regier JC; Mitter C; Poole RW; Matthews M 《Molecular biology and evolution》1997,14(4):381-390
To test its phylogenetic utility, nucleotide sequence variation in a
1,240-bp fragment of the elongation factor-1 alpha (EF-1 alpha) gene was
examined in 49 moth species representing the major groups of the
superfamily Noctuoidea. Both parsimony and distance analyses supported the
monophyly of nearly all groups for which there are clear morphological
synapomorphies. Clades of subfamily rank and lower, probably mid-Tertiary
and younger, were strongly supported. The third codon position contains 88%
of variable sites, and approaches saturation at approximately 20% sequence
divergence, possibly due to among-site rate heterogeneity and composition
bias; higher divergences occur only in association with shifts in
composition. Surprisingly, the few nonsynonymous changes appear no more
phylogenetically reliable than synonymous changes. Signal strength for
basal divergences is weak and fails to improve with character weighting;
thus, dense taxon sampling is probably needed for strong inference from
EF-1 alpha regarding deeper splits in Noctuoidea (probably early Tertiary).
EF-1 alpha synonymous changes show promise for phylogeny reconstruction
within Noctuidae and other groups of Tertiary age.
相似文献
87.
K N Hawkins R J Knapp D R Gehlert G K Lui M S Yamamura L C Roeske V J Hruby H I Yamamura 《Life sciences》1988,42(25):2541-2551
[3H]H-D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 ([3H]CTOP), a potent and highly selective mu opioid antagonist, was used to localize the mu receptors in rat brain by light microscopic autoradiography. Radioligand binding studies with [3H]CTOP using slide-mounted tissue sections of rat brain produced a Kd value of 1.1 nM with a Bmax value of 79.1 fmol/mg protein. Mu opioid agonists and antagonists inhibited [3H]CTOP binding with high affinity (IC50 values of 0.2-2.4 nM), while the delta agonist DPDPE, delta antagonist ICI 174,864, and kappa agonist U 69, 593 were very weak inhibitors of [3H]CTOP binding (IC50 values of 234-3631 nM). Light microscopic autoradiography of [3H]CTOP binding sites revealed regions of high density (nucleus of the solitary tract, clusters in the caudate-putamen, interpeduncular nucleus, superior and inferior colliculus, subiculum, substantia nigra zona reticulata, medial geniculate, locus coeruleus and dorsal motor nucleus of the vagus) and regions of moderate labeling (areas outside of clusters in the caudate-putamen, cingulate cortex, claustrum and nucleus accumbens). The cerebral cortex (parietal) showed a low density of [3H]CTOP binding. 相似文献
88.
Immunoglobulins raised from Saccharomyces cerevisiae a and alpha mating type cell envelope preparations inhibited alpha factor mediated morphogenesis of the a cell without inhibiting normal cell division. The Ig responsible for this inhibition was absorbed to both a and alpha whole cells and heat-killed cells, indicating that the immunoglobulin binding sites were exposed on the cell surface and not mating type specific. Additionally, alpha factor mediated cell cycle arrest was not affected by the immunoglobulin preparations, implying that the immunoglobulin was not preventing alpha factor from binding to its receptor. 相似文献
89.
C J Fiol A M Mahrenholz Y Wang R W Roeske P J Roach 《The Journal of biological chemistry》1987,262(29):14042-14048
The mechanism for synergistic phosphorylation by glycogen synthase kinase 3 (GSK-3) and casein kinase II was studied using a synthetic peptide which contains the sequence of a potentially important proline/serine-rich regulatory region of rabbit muscle glycogen synthase. The peptide, Ac-PRPAS(3a)VPPS(3b)PSLS(3c)RHSS(4)PHQS(5) EDEEEP-amide, has five known phosphorylation sites of the native enzyme designated sites 3a, 3b, 3c, 4, and 5, which are spaced every fourth residue. The peptide was phosphorylated specifically at site 5 by casein kinase II with an apparent Km of 23 microM, but it was not phosphorylated by GSK-3. However, after initial phosphorylation of site 5 by casein kinase II, the peptide became an effective substrate for GSK-3 with an apparent Km of 2 microM. GSK-3 introduced up to four phosphates and appeared to catalyze the sequential modification of sites 4, 3c, 3b, and 3a, respectively. The results can be explained if GSK-3 recognizes the sequence -SXXXS(P). Phosphorylation of site 5 by casein kinase II creates this recognition site. Thereafter, each successive phosphorylation introduced by GSK-3 generates a new recognition site. The results provide a molecular basis to explain the synergistic action of casein kinase II and GSK-3 that is also observed with native glycogen synthase. In addition, this investigation emphasizes how protein recognition sites in some cellular targets may have to be formed post-translationally. 相似文献
90.
The active site(s) of the bifunctional regulatory protein of pyruvate,orthophosphate dikinase catalyze(s) the Pi-dependent activation (dephosphorylation) and ADP-dependent inactivation (phosphorylation) of maize leaf dikinase. The chemical modification studies of the regulatory protein active sites presented in this paper are interpreted as showing the two sites to be physically distinct. Pyridoxal 5'-phosphate and 2-nitro-5-thiocyanatobenzoate (NTCB) selectively inhibit the dikinase activating site, which is protected by the nonprotein substrate, Pi. Phenylglyoxal blocks both the activation and inactivation sites; the former is protected selectively by Pi and the latter by both the nonprotein substrate, ADP, and Pi. The Pi that protects the inactivation site is distinct from the activation substrate. Inhibition studies show Pi to be a parabolic competitive inhibitor of the ADP-dependent inactivation of dikinase, implying that besides substrate Pi, a second phosphate also binds to the regulatory protein. The above chemical modifications are not mutually exclusive; neither NTCB, 5,5'-dithiobis-(2-nitrobenzoate), nor pyridoxal 5'-phosphate blocks subsequent modification of the activation site by phenylglyoxal. Similarly, prior modification with NTCB does not affect modification by pyridoxal 5'-phosphate. 相似文献