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[en] Radioiodine labeled tyrosine analogues, such as L-3[I-123]iodo-α-methyltyrosine, have been used for the evaluation of cerebral amino acid transport. Furthermore, these could be used for the tumor grading. We added one methyl-group to the L-3-α-methyltyrosine, expecting the increased cellular membrane permeability. The aim of this study was to evaluate the feasibility of OMIMT as an agent for tumor image. After synthesis of o-methyl-L-α-methyltyrosine (OMAMT), OMAMT was labeled with I-131 using Iodogen method. Synthesis of [I-131] IMT was performed as previously described (C. Krummeich et al. J. Appl. Rad. Isot, 45: 929, 1994). Uptake and retention studies were performed using 9L gliosarcoma cells (106) at various time points upto 4 hr. OMIMT uptake was 2.5 times higher than IMT uptake at 60 min and same after 2hr. Female Fischer rats were implanted with the 9L gliosarcoma cell line into right thigh. The biodistribution (five rats per group) was evaluated (30 min, 2hr, 24hr) after iv injection of 3.7 MBq I-131 labeled OMIMT and IMT. Maximum accumulation in tumors occurred at 30 min for both OMIMT and IMT. The tumor uptake of OMIMT was significantly higher than that of IMT at early time point studied (3.74 vs 0.38 %ID/g at 30 min and 2.40 vs 0.24 %ID/g at 2 hr, respectively). However, The tumor uptakes of both radiolabels were similar at 24 hr (0.04 vs 0.05 %ID/g, respectively). The kidney was the major route of elimination and had the greater accumulation (23.98 vs 4.03 %ID/g at 30 min). Gamma camera images were obtained at 30 min , 2 hr and 24 hr. Tumor was visualized as early as at 30 min. These data suggested that [I-131]OMIMT might be useful as a tumor imaging agent and had advantage for the tumor image
[en] Metastatic disease is present at diagnosis in 30% of the patients with colorectal cancer (CRC), and approximately half of early-stage patients with CRC will eventually present with metastatic disease. Until recently, few chemotherapy options were available to treat metastatic colorectal carcinoma (MCRC). Fluorouracil (5-FU) with leucovorin (LV) modulation has a marginal but positive effect on survival in those patients. The recent incorporation of irinotecan (CPT -11) and oxaliplatin for the management of advanced CRC has generated further improvement in survival. The development of oral fluoropyrimidines, mimicking continuous infusion 5-FU, is convenient to use. Recently completed or ongoing clinical trials to study novel targeting agents have initiated a new era of drug development. Anti-angiogenesis drugs, tyrosine kinase inhibitors, and epidermal growth factor blockers are among the new generation of agents. (author)
[en] The extensive collection of NOE constraint data involving the aromatic ring signals is essential for accurate protein structure determination, although it is often hampered in practice by the pervasive signal overlapping and tight spin couplings for aromatic rings. We have prepared various types of stereo-array isotope labeled phenylalanines (ε- and ζ-SAIL Phe) and tyrosine (ε-SAIL Tyr) to overcome these problems (Torizawa et al. 2005), and proven that these SAIL amino acids provide dramatic spectral simplification and sensitivity enhancement for the aromatic ring NMR signals. In addition to these SAIL aromatic amino acids, we recently synthesized δ-SAIL Phe and δ-SAIL Tyr, which allow us to observe and assign δ-13C/1H signals very efficiently. Each of the various types of SAIL Phe and SAIL Tyr yields well-resolved resonances for the δ-, ε- or ζ-13C/1H signals, respectively, which can readily be assigned by simple and robust pulse sequences. Since the δ-, ε-, and ζ-proton signals of Phe/Tyr residues give rise to complementary NOE constraints, the concomitant use of various types of SAIL-Phe and SAIL-Tyr would generate more accurate protein structures, as compared to those obtained by using conventional uniformly 13C, 15N-double labeled proteins. We illustrated this with the case of an 18.2 kDa protein, Escherichia coli peptidyl-prolyl cis-trans isomerase b (EPPIb), and concluded that the combined use of ζ-SAIL Phe and ε-SAIL Tyr would be practically the best choice for protein structural determinations.
[en] Nipah virus (NiV) is a zoonotic biosafety level 4 paramyxovirus that emerged recently in Asia with high mortality in man. NiV is a member, with Hendra virus (HeV), of the Henipavirus genus in the Paramyxoviridae family. Although NiV entry, like that of other paramyxoviruses, is believed to occur via pH-independent fusion with the host cell's plasma membrane we present evidence that entry can occur by an endocytic pathway. The NiV receptor ephrinB2 has receptor kinase activity and we find that ephrinB2's cytoplasmic domain is required for entry but is dispensable for post-entry viral spread. The mutation of a single tyrosine residue (Y304F) in ephrinB2's cytoplasmic tail abrogates NiV entry. Moreover, our results show that NiV entry is inhibited by constructions and drugs specific for the endocytic pathway of macropinocytosis. Our findings could potentially permit the rapid development of novel low-cost antiviral treatments not only for NiV but also HeV.
[en] The sequence of amino acids in peptide chains consisting of proteins is the most fundamental information of living things. A direct and nondestructive method of reading is highly required as an alternative to the method based on the gene analysis. Luminescence detection is a very sensitive tool for investigating various materials. In order to find characteristic luminescence of each amino acid we study L-cysteine and L-tyrosine using UV laser of 3.36 eV with pulse duration of 1.5 ps. In addition to a common 2.66 eV band of the luminescence we have found 2.89 eV band for L-cysteine and 2.92 eV band for L-tyrosine. It can be interpreted that the side chain makes difference on the luminescence by affecting the peptide linkage or carbonyl group. - Highlights: • Luminescence from L-cysteine and L-tyrosine are studied. • Analyzing the luminescence enables to distinguish those two amino acids. • The lifetimes and the peak photon energies under UV laser excitation are presented.
[en] Recent neuropathological studies have shown that Fluoro-Jade C (FJC), an anionic fluorescent dye, is a good marker of degenerating neurons. However, those studies have mostly examined acute rather than chronic models of neurodegeneration. We therefore compared FJC staining using the intrastriatal 6-hydroxydopamine (6-OHDA)-injected rat as an acute model and the zitter rat as a chronic model, as both show dopaminergic (DA) neurodegeneration. In the 6-OHDA-injected rat, FJC-positive neurons were found in the substantia nigra pars compacta (SNc) before the loss of tyrosine hydroxylase (TH)-positive DA neurons. In the zitter rat, FJC-labeled fibers were first detected at 1 month old (1M) and were considerably increased in the striatum at 4M, whereas FJC-labeled cell bodies were found at 4M, but not at 1M in the SNc. Furthermore, FJC-labeled neurons of the zitter rat showed TH-immunoreactivity in fibers, but little in cell bodies, while those from the 6-OHDA-injected rat showed TH-immunoreactivity even in the cell bodies. These results demonstrate that FJC is a useful tool for detecting chronically degenerating neurons, and suggest that intracellular substances bound to FJC may accumulate in the cell bodies from fibers at a slower rate in the chronic model than in the acute model
[en] Breast tumor development and progression are thought to occur through a complex, multistep process, including oncogene activation (eg HER2/neu) and mutation or loss of tumor suppressor genes (eg p53). Determining the function of genetic alterations in breast carcinoma tumorigenesis and metastasis has been the focus of intensive research efforts for several decades. One group of proteins that play a critical role in breast cancer cell signaling pathways are tyrosine kinases. Overexpression of the tyrosine kinase HER2/neu is observed in many human breast cancers and is positively correlated with enhanced tumorigenesis . Recently, another tyrosine kinase, Syk, has been implicated as an important inhibitor of breast cancer cell growth and metastasis . This recent finding was unexpected, since Syk function has been predominantly linked to hematopoietic cell signaling, and is discussed further in this commentary
[en] Tritium labelled splenopentine (Arg-Lys-Glu-Val-Tyr-OH) and diacetylsplenopentine (Nα-ac-Arg-Nε-ac-Lys-Glu-Val-Tyr-OH) were prepared by the catalytic dehalotritiation of the corresponding diiodopeptides obtained by ICl-iodination. Under conditions which proved to be optimal in foregoing model deuterations, a specific radioactivity of about 90% of the theoretical one was achieved. The labelling result was influenced noticeably by a transfer of solvent hydrogen directly to the substrate analogously as found in the dehalodeuterations of simple amino acid derivatives. (author)
[en] A time-dependent change in the ultraviolet absorbance at 285 nm of the phenol ring of tyrosine has been observed in a stopped-flow spectrophotometer, when tyrosine was rapidly transferred from water into deuterium oxide (the final tyrosine concentration was about 1 mM). From this experiment, the rate constant (k/sub e/) of the hydrogen-deuterium exchange reaction of the tyrosine OH group has been determined at various pH values and at several temperatures. At pH 6.1 and 110C, for example, k/sub e/ was found to be as high as 70 s-1. The stopped-flow ultraviolet spectroscopy has also been used for a measurement of hydrogen exchange rates at the six tyrosine residues of bovine pancreatic ribonuclease A