[Phase correction technology research and improvement based on single-sided interferograms in FTIR]

In the Fourier transform infrared spectrometers the interferograms are usually sampled by the means of the single-side beyond zero path difference and the interferograms are asymmetric. These phase-corrected technologies are researched and improved in the present paper. In the Mertz method which requires apodization to be higher, the interferograms are apodized by these asymmetric windows so that the width of the main lobe increases and spectral resolution reduced. In order to solve these problems, a method which combines the Mertz and Forman methods is presented in the paper. In the method a double-side interferogram is constructed by the mirrored processing of the single-side interferogram beyond zero path difference, followed by the symmetric apodization, fast Fourier transform (FFT) to rebuild spectrum. And in the method high resolution phase spectrum is computed by the symmetrization of double-side interfergram to improve the phase-correction accuracy. In the experiment, these asymmetric window functions have the lower resolution compared with these symmetric window functions. And the spectrum which is acquired by the improved phase corrected method is compared with the spectra which are acquired by the Mertz and Forman methods, and the improved method has less error than Mertz, less computation than Forman, and the spectral resolution achieved 2 cm(-1).

Glucuronide-sulfate diconjugate as a novel metabolite of glycyrrhetic acid in rat bile

To study the metabolites of glycyrrhetic acid (GA) in rat bile, an analytical method was developed to identify GA and its metabolites by liquid chromatography mass spectrometry (LC-MS). Rat bile was collected after i.v. injection of GA. Three major GA-related peaks were detectable in rat bile by high-performance liquid chromatography (HPLC) analysis at 254 nm. LC-MS spectra showed their protonated molecular ions at m/z 727, 647, and 551. Furthermore, the three metabolites were also confirmed to exist in rat bile on LC-MS total ion chromatogram (TIC). Taken together with the susceptible nature to beta-glucuronidase digestion and alkaline conditions, they were identified to be a novel sulfate-glucuronide diconjugate and the known monoglucuronide and sulfate conjugate, respectively.

Determination of 5-aminoimidazole-4-carboxamide in human plasma by ion-pair extraction and LC–MS/MS

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was established for the determination of 5-aminoimidazole-4-carboxamide (AICA) in human plasma. The method included a solvent extraction of AICA as an ion pair with 1-pentanesulfonate ion and a separation on a Hypersil ODS2 column with the mobile phase of methanol-water (68:32, v/v). Determination was performed using an electrospray ionization source in positive ion mode (ESI(+)). Multiple reaction monitoring (MRM) was utilized for the detection monitoring m/z at 127-->110 for AICA, and 172-->128 for IS. The calibration curve was linear within a range from 20 to 2000 ng/mL and the limit of quantity for AICA in plasma was 20 ng/mL. RSD of intra-assay and inter-assay were no more than 5.90% and 5.65%.

The negative cell cycle regulator, Tob (transducer of ErbB-2), is a multifunctional protein involved in hippocampus-dependent learning and memory

Tob (transducer of ErbB2) is a negative cell cycle regulator with anti-proliferative activity in the periphery. Using a behavioral screening paradigm to look for novel gene functions in the brain, we identified Tob as a brain-expressed protein involved in learning and memory. Behavioral training of fear-conditioning triggered a transient elevation of Tob protein, which preceded the formation of long-term memory. Functional perturbation of Tob by intra-CA1 infusion of antisense oligonucleotides in rats impaired spatial learning and memory in the Morris water maze and long-term memory for contextual fear conditioning, two behavioral paradigms that require the hippocampus. Furthermore, long-term potentiation was suppressed by Tob antisense infusion into the CA1 region. Together, these results indicate that the negative cell cycle regulator Tob is a multifunctional protein involved in hippocampus-dependent learning and memory.

Wnt-1 promotes neuronal differentiation and inhibits gliogenesis in P19 cells

Wnt-1, the vertebrate counterpart of the Drosophila wingless gene, plays an important role in the early morphogenesis of neural tissues. In this report, we have shown that overexpression of Wnt-1 can direct embryonic carcinoma P19 cells to differentiate into neuron-like cells in the absence of retinoic acid. Immunocytochemistry showed that these cells expressed neuronal markers, such as the neurofilament (NF) and microtubule-associated protein 2 (MAP2), but failed to express the glial cell marker, glial fibrillary acidic protein (GFAP). RT-PCR revealed that two basic helix-loop-helix (bHLH) genes, Mash-1 and Ngn-1, were up-regulated during the differentiation stage of Wnt-1-overexpressing P19 cells. These results suggest that the Wnt-1 gene promotes neuronal differentiation and inhibits gliogenesis during the neural differentiation of P19 cells, and that neural bHLH genes might be involved in this process.

Mouse nestin cDNA cloning and protein expression in the cytoskeleton of transfected cells

Complementary DNA (cDNA) corresponding to mouse nestin intermediate filament protein, a specific marker for neural stem cells, was isolated and characterized. The complete sequence comprised 5983 base pairs encoding 1821 amino acids, and the deduced polypeptide was similar to rat (84%), hamster (73%), and human (62%) nestin. Southern blots showed that mouse nestin was a single-copy gene, and Northern blots detected a 6.0 kilobase mRNA transcript. When the cDNA was overexpressed as an enhanced green fluorescent fusion protein in COS7 cells, nestin immunoreactivity appeared in the filamentous cytoskeletal network. Accordingly, biologically active mouse nestin cDNA may offer an important new tool for stem cell research.

Rational drug design of DNA oligonucleotides as HIV inhibitors

DNA oligonucleotides as anti-HIV therapeutic agents have been developed for more than a decade. Numbers of oligonucleotides have been designed as potential anti-HIV inhibitors. Here we summarized the designed anti-viral oligonucleotides in last decade and divided the designed DNA HIV inhibitors into three categories: (i) antisense inhibitors, (ii) triplex inhibitors and (iii) G-quartet inhibitors, based upon their inhibitory mechanism and structures. Also we proposed a strategy of rational drug design of anti-HIV oligonucleotides, which includes several critical steps, such as (1) structure-based rational drug design, (2) chemical synthesis/combinational chemistry, (3) the determination of structural properties, (4) assays of the inhibition of HIV-1 IN and virus replication, and (5) 3D QSAR operation. This methodology has been used by the design of G-quartet inhibitors.

Structure-activity of inhibition of HIV-1 integrase and virus replication by G-quartet oligonucleotides

As novel anti-HIV agents, the G-tetrad-forming oligonucleotides have been explored for their structure-activity relations with regard to inhibition of integrase (IN) (N. Jing, Expert Opin. Investig. Drugs (2000) 9, 1777-1785). We have now developed two families of G-quartet oligonucleotides: T40217-T40222, with potential formation of a tail-to-tail G-quartet dimer, and T40224-T40227, with phosphorothioate (PT) linkages in the guanine loops. The results obtained from biophysical measurements and the assays of the inhibition of HIV-1 IN and virus replication demonstrated that an increase in the length of the G-quartet structure from a monomer (15A) to a tail-to-tail dimer (47A) does not distinctly disrupt the inhibition of HIV-1 IN activity or the inhibition of HIV-1 replication in cell cultures. G-quartet oligonucleotides were observed to induce molecular aggregation of HIV-1 IN and interrupt the binding of viral DNA to HIV-1 IN. Also, PT substitutions did not confer any advantages compared with the regular phosphodiesters for the inhibition of HIV-1 replication by intramolecular G-quartets. The G-quartet motif is the primary requirement for the remarkable nuclease resistance and pronounced biological efficacy of these oligonucleotides.

A role of N-cadherin in neuronal differentiation of embryonic carcinoma P19 cells

N-cadherin is one of the important molecules for cell to cell interaction in the development of the central nervous system (CNS). In this report, we have shown that N-cadherin mRNA and protein were increased rapidly in retinoic acid (RA)-induced neuronal differentiation of embryonic carcinoma P19 cells. To explore possible roles for N-cadherin during this process, N-cadherin-overexpressing P19 cell lines were established. These transfected cells could differentiate into neurofilament-expressing neurons in the absence of RA. RT-PCR revealed that the expression patterns of development-related genes, such as Oct-3/4, nestin, Notch-1, and Mash-1 were similar between the transfected P19 cells and the RA-induced wild-type P19 cells during their neuronal differentiation. On the contrary, the Wnt-1 gene was up-regulated in the N-cadherin-overexpressing P19 cells, but could not be detected in the wild-type P19 cells. These results suggest N-cadherin may play a role in neuronal differentiation of P19 cells, possibly through the Wnt-1 signaling pathway.

Identification of differentially expressed genes in the denervated rat hippocampus by cDNA arrays

To elucidate the molecular mechanism underlying the physiological responses to injury in the central nervous system, gene expression profiles in rodent hippocampus following perforant path transection were investigated using cDNA array hybridization. Of the 8000 arrayed clones, 47 exhibited differential expression by >3-fold difference in the denervated hippocampus from control, with 15 up-regulated and 22 down-regulated. They can be functionally assigned into several classes, among which the most prominent are those coding proteins involved in macromolecules synthesis and processing. Northern blot analysis verified the validation of the aforementioned array data. These results throw some new light on the physiological responses of the hippocampus to entorhinal deafferentation at molecular level.

Mouse nestin protein localizes in growth cones of P19 neurons and cerebellar granule cells

The neuronal growth cone, a highly motile structure at the distal tip of growing axons, contains filamentous actin and microtubules as its main cytoskeletal components. Using immunocytochemistry, we observed that nestin, which is the predominant intermediate filament protein in neuroepithelial cells and young neurons of the developing brain, appears to be strongly expressed in neurites and growth cones of neurons differentiating from P19 embryonic carcinoma cells in vitro. Double-staining of nestin and microtubule-associated protein-2 as well as nestin and growth-associated protein-43 revealed that nestin protein localizes in neurites and the central regions of growth cones of primary cultures of cerebellar granule cells from postnatal day 6 mice. These results suggest a role for nestin in growth cone guidance during axon elongation.

cDNA cloning and functional expression of growth hormone receptor from soft-shelled turtle (Pelodiscus sinensis japonicus)

The growth hormone receptor (GHR) cDNA was cloned from the liver of soft-shelled turtle (Pelodiscus sinensis japonicus) using the polymerase chain reaction (PCR). Although GHR has been cloned from several mammalian and avian species, this is the first description of the reptilian receptor. As deduced from the nucleotide sequence, the precursor GHR of soft-shelled turtle (tGHR) is a protein of 615 amino acids which presents 72% identity with the chicken receptor and 57-64% identity with GHRs of several mammals. The tGHR expressed in COS-7 cells specifically bound human growth hormone (hGH) and was able to transduce an activation of transcription in the transfected cells. Binding of (125)I-hGH to the expressed receptor was decreased by the addition of excess unlabeled hGH, pig GH, and bream GH but not by pig insulin. The open reading frame of tGHR cDNA was inserted into the pSINrep/gfp (green fluorescence protein) vector and the tGHR-gfp fusion protein was stably expressed in baby hamster kidney (BHK) cells. Confocal imaging showed that tGHR-gfp was largely concentrated on the plasma membrane. Western blot analysis and deglycosylation treatment with PNGase F demonstrated that tGHR was a glycoprotein in BHK cells.

Developing G-quartet oligonucleotides as novel anti-HIV agents: focus on anti-HIV drug design

Recently, a new class of oligonucleotides, forming G-quartet structures, has been developed as novel anti-HIV agents. Several critical structure-activity relationships between HIV-1 integrase and G-quartet oligonucleotides have been demonstrated. In addition the mechanism of the inhibition of HIV-1 integrase by G-quartet oligonucleotides, such as T30695 and its derivatives, has been explored. This review summarises the preliminary studies of developing G-quartet oligonucleotides as novel anti-HIV agents in several aspects including structure-activity relationship, stability-activity correlation, mechanism of HIV-1 integrase inhibition, substitution of phosphorothioates and targeting HIV-1 integrase in infected cells, which, hopefully, could help for developing a novel, efficient anti-HIV agent.

Mechanism of inhibition of HIV-1 integrase by G-tetrad-forming oligonucleotides in Vitro

The G-tetrad-forming oligonucleotides and have been identified as potent inhibitors of human immunodeficiency virus type 1 integrase (HIV-1 IN) activity (Rando, R. F., Ojwang, J., Elbaggari, A., Reyes, G. R., Tinder, R., McGrath, M. S., and Hogan, M. E. (1995) J. Biol. Chem. 270, 1754-1760; Mazumder, A., Neamati, N., Ojwang, J. O., Sunder, S., Rando, R. F., and Pommier, Y. (1996) Biochemistry 35, 13762-13771; Jing, N., and Hogan, M. E. (1998) J. Biol. Chem. 273, 34992-34999). To understand the inhibition of HIV-1 IN activity by the G-quartet inhibitors, we have designed the oligonucleotides and, composed of three and four G-quartets with stem lengths of 19 and 24 A, respectively. The fact that increasing the G-quartet stem length from 15 to 24 A kept inhibition of HIV-1 IN activity unchanged suggests that the binding interaction occurs between a GTGT loop domain of the G-quartet inhibitors and a catalytic site of HIV-1 IN, referred to as a face-to-face interaction. Docking the NMR structure of (Jing and Hogan (1998)) into the x-ray structure of the core domain of HIV-1 IN, HIV-1 IN-(51-209) (Maignan, S., Guilloteau, J.-P. , Qing, Z.-L., Clement-Mella, C., and Mikol, V. (1998) J. Mol. Biol. 282, 359-368), was performed using the GRAMM program. The statistical distributions of hydrogen bonding between HIV-1 IN and were obtained from the analyses of 1000 random docking structures. The docking results show a high probability of interaction between the GTGT loop residues of the G-quartet inhibitors and the catalytic site of HIV-1 IN, in agreement with the experimental observation.

Nestin expression during mouse eye and lens development

Nestin is an intermediate filament protein, which is expressed predominantly in the developing central nervous system and skeletal muscles. In situ hybridization revealed that mouse nestin mRNA is in the optic stalk at 9.0 days post coitus (dpc) and in the lens vesicle at 10.0 dpc. From 14.5 dpc onward, nestin transcripts appear in lens fibers and neuroretina. Immunohistochemistry showed that nestin protein appears in the optic stalk at 9.5 dpc and in the posterior lens epithelium at 10.5 dpc. By 12.5 dpc, it is found in the lens, neuroretina, and optic stalk as well as in developing extrinsic ocular muscle, and it localizes in lens epithelium, optic disc, and optic nerve from 14.5 dpc to postnatal day 1. In adult eye, nestin protein appears in the optic nerve.

[Mechanism of impairment to microtubule polymerization resulting from zinc deficiency during pregnancy and lactation in mice]

To probe into the mechanism of zinc deficiency on microtubule polymerization impairment, the learning ability and the levels of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 expression in the brain of zinc deficient offsprings, maternal ICR mice were fed with experiment diets containing different levels of zinc(1, 5, 30 and 100 mg/kg) during pregnancy and lactation respectively. On the postnatal day 70 of offsprings, the learning ability and the expression of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 in the brain were examined by shuttle box and Western blot assays respectively. The results showed that the number of trials needed to reach the learning criterion for zinc deficient groups (1 and 5 mg/kg) was much higher than that for non zinc deficient groups (30 and 100 mg/kg). The levels of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 expression in the brain of zinc deficient offsprings (1 and 5 mg/kg) were lower than those in the brain of offsprings whose dams fed with zinc adequately supplied diet (30 mg/kg) and zinc supplemented supplied diet (100 mg/kg) respectively. These results suggested that the inhibition of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 expression might be the most important mechanism of microtubule polymerization decline resulting from zinc deficiency, which had close relationship with brain function impairment.

Stability-activity relationships of a family of G-tetrad forming oligonucleotides as potent HIV inhibitors. A basis for anti-HIV drug design

Recently, we have demonstrated that T30695, a G-tetrad-forming oligonucleotide, is a potent inhibitor of human immunodeficiency virus, type I (HIV-1) integrase and the K(+)-induced loop folding of T30695 plays a key role in the inhibition of HIV-1 integrase (Jing, N., and Hogan, M. E. (1998) J. Biol. Chem. 273, 34992-34999). Here we have modified T30695 by introducing a hydrophobic bulky group, propynyl dU, or a positively charged group, 5-amino dU, into the bases of T residues of the loops, and by substitution of the T-G loops by T-T loops. Physical measurements have demonstrated that the substitution of propynyl dU or 5-amino dU for T in the T residues of the loops did not alter the structure of T30695, and these derivatives also formed an intramolecular G-quartet structure, which is an essential requirement for anti-HIV activity. Measured IC(50) and EC(50) values show that these substitutions did not induce an apparent decrease in the ability to inhibit HIV-1 integrase activity and in the inhibition of HIV-1 replication in cell culture. However, the substitution of T-T loops for T-G loops induced a substantial decrease in both thermal stability and anti-HIV activity. The data analysis of T30695 and the 21 derivatives shows a significant, functional correlation between thermal stability of the G-tetrad structure and the capacity to inhibit HIV-1 integrase activity and between thermal stability of the G-tetrad structure and the capacity to inhibit HIV-1 replication, as assessed with the virus strains HIV-1 RF, IIIB, and MN in cell culture. This relationship between thermostability and activity provides a basis for improving the efficacy of these compounds to inhibit HIV-1 integrase activity and HIV-1 replication in cell culture.

Structure-activity of tetrad-forming oligonucleotides as a potent anti-HIV therapeutic drug

Recently, we have described the design and characterization of oligonucleotides containing only G and T bases, i.e. T30695 and T30177, that are potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in culture (Jing, N., Rando, R. F., Pommier, Y., and Hogan, M. E. (1997) Biochemistry 36, 12498-12505). To understand that observation and to rationalize the generally high thermal stability of oligonucleotide folding for these compounds, we have used NMR methods, coupled to molecular modeling, to obtain a high resolution structure model for T30695, which is the most potent of the integrase inhibitors that have been identified thus far. Modeling and NMR data obtained in the presence of Li+ ions show that T30695 assumes an intramolecular fold with a distorted G-octet core and a set of three open, partially disordered loops. This is referred to as Li+-form structure. The NMR-based model suggests that, upon coordination with three K+ equivalents, the central G-octet becomes more regular and that the loop domains become orderly and compact. This is referred to as K+-form structure. Based upon the assay of inhibition of HIV-1 integrase, T30695 demonstrated a strong inhibition of HIV-1 integrase activity as the K+-form structure, but a poor inhibition of HIV-1 integrase activity as the Li+-form structure. The structure/activity analysis suggests that the K+-induced conformation transition of the tetrad-forming oligonucleotides, such as T30695 and T30177, plays a key role in inhibition of HIV-1 integrase activity.

A common region of allelic loss on chromosome region 3p25.3-26.3 in nasopharyngeal carcinoma

Loss of heterozygosity (LOH) of chromosome arm 3p has been commonly observed in carcinomas of various tissues, including those of nasopharyngeal carcinoma (NPC). To determine the frequency and extent of allelic loss in NPC, we investigated 16 loci on chromosome bands 3p21-26 in 24 tumor tissues by microsatellite analysis. LOH on 3p21-26 was found in 16 of 24 (66.7%) tumors. The highest frequency of allelic loss was found in two adjacent loci, D3S1620 (11/22, 50%) and D3S1560 (9/18, 50%). Eight cases showed LOH in one contiguous region and 5 cases in more than one region. Samples 1, 3, 4, 7, 8, 10, 16, 17, 18, 19, and 22 had a contiguous stretch of allelic loss between D3S1297 and D3S1597. The smallest common LOH/deletion region seems likely to lie between D3S1297 (3p26.3-26.2) and D3S1560 (3p25.3). The allelic loss map defined here will facilitate finer mapping of putative tumor suppressor gene loci and positional cloning of such genes, which may play a role in carcinogenesis of NPC.