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Biomedical subjects

Z Gu

Publications and source records attributed to Z Gu.

At least 19 recordsLinked to original sources
PubMed2006

In vitro antiretroviral activity and in vitro toxicity profile of SPD754, a new deoxycytidine nucleoside reverse transcriptase inhibitor for treatment of human immunodeficiency virus infection.

SPD754 (AVX754) is a deoxycytidine analogue nucleotide reverse transcriptase inhibitor (NRTI) in clinical development. These studies characterized the in vitro activity of SPD754 against NRTI-resistant human immunodeficiency virus type 1 (HIV-1) and non-clade B HIV-1 isolates, its activity in combination with other antiretrovirals, and its potential myelotoxicity and mitochondrial toxicity. SPD754 was tested against 50 clinical HIV-1 isolates (5 wild-type isolates and 45 NRTI-resistant isolates) in MT-4 cells using the Antivirogram assay. SPD754 susceptibility was reduced 1.2- to 2.2-fold against isolates resistant to zidovudine (M41L, T215Y/F, plus a median of three additional nucleoside analogue mutations [NAMs]) and/or lamivudine (M184V) and was reduced 1.3- to 2.8-fold against isolates resistant to abacavir (L74V, Y115F, and M184V plus one other NAM) or stavudine (V75T/M, M41L, T215F/Y, and four other NAMs). Insertions at amino acid position 69 and Q151M mutations (with or without M184V) reduced SPD754 susceptibility 5.2-fold and 14- to 16-fold, respectively (these changes gave values comparable to or less than the corresponding values for zidovudine, lamivudine, abacavir, and didanosine). SPD754 showed similar activity against isolates of group M HIV-1 clades, including A/G, B, C, D, A(E), D/F, F, and H. SPD754 showed additive effects in combination with other NRTIs, tenofovir, nevirapine, or saquinavir. SPD754 had no significant effects on cell viability or mitochondrial DNA in HepG2 or MT-4 cells during 28-day exposure at concentrations up to 200 microM. SPD754 showed a low potential for myelotoxicity against human bone marrow. In vitro, SPD754 retained activity against most NRTI-resistant HIV-1 clinical isolates and showed a low propensity to cause myelotoxicity and mitochondrial toxicity.

Anti-HIV Agents↗
PubMed2006

Preparation and characterization of EP-liposomes and Span 40-niosomes.

Clotrimazole, an imidazole derivative antifungal agent, has been widely used for the treatment of mycotic infections of the genitourinary tract. In order to develop alternative formulations for the vaginal administration of clotrimazole which would provide sustained and controlled release of the appropriate drug for local vaginal therapy, liposomes/niosomes were evaluated as delivery vehicles. To optimize the preparation of the liposomes/niosomes with regard to size and entrapment efficiency, multilamellar liposomes/ niosomes containing the drug were prepared by a lipid hydration method. The liposomes/niosomes thus prepared were evaluated for their stability as drug-loaded liposomes/niosomes in simulated vaginal fluid at 37 +/- 1 degrees C. The two vesicle systems were also evaluated with regard to rat and rabbit vaginal irritation.

Animals↗
PubMed2005

Type II collagen and aggrecan mRNA expressions in rabbit condyle following disc displacement.

The aim of this investigation was to study the remodelling of cartilage in the mandibular condyle following disc displacement (DD) of the temporomandibular joint (TMJ). Forty adult Japanese white rabbits were used in this study. The right joints of 28 of the 40 rabbits had their discs surgically displaced. Four of the 28 were killed at 4 days or 1, 2, 4, 6, 8 and 12 weeks after surgery. The messenger RNA (mRNA) expression levels of aggrecan and type II collagen in cartilages were measured using in situ hybridization techniques. Results showed that aggrecan mRNA expression reduced in the first week after DD. The expression began to recover after 4 weeks and reached a normal level after 6 weeks. Type II collagen mRNA expression reduced from 4 weeks and the expression recovered after 8 weeks. This suggests that the chondrocyte reacting to the displacement of the TMJ disc, alters its matrix gene expression patterns and it is may be the cause of the shape changes of TMJ after DD.

Aggrecans↗
PubMed2003

Multiplexed, real-time PCR for quantitative detection of human adenovirus.

Adenovirus infection is becoming increasingly recognized as a cause of morbidity and mortality in the immunosuppressed patient population. While early detection and quantitation of adenovirus in peripheral blood has been suggested as a means of directing and monitoring antiviral therapy in these patients, few methods have been published, particularly with respect to viral quantitation. A multiplexed real-time PCR assay was developed that can quantitatively detect a wide range of known serotypes of human adenovirus, including all of subgroups A to C. This assay was compared to a qualitative, Southern blot-based PCR assay by using 45 peripheral blood specimens from 16 patients. There was 100% concordance between the two tests in terms of qualitative results. The real-time assay detected adenovirus in patient samples at levels from <200 to 266,681 copies/ml of blood. By using control viral samples, sensitivity was demonstrated to less than 10 copies of viral genome per reaction and quantitative linearity was demonstrated from 10 to 10(6) copies of input viral DNA. Equivalent sensitivity and linearity were demonstrated for 15 different reference serotypes of adenovirus. Eleven other viral serotypes have complete target region sequence homology to one or more of the strains tested. No cross-reactivity was noted with other commonly isolated viral species. Sequence analysis showed no significant homology with any other human pathogens (bacterial or viral). This assay allows rapid, sensitive, and specific quantitation of adenovirus and may have a significant impact on the care of immunocompromised patients at risk for disseminated viral infection.

Adenovirus Infections, Human↗
PubMed2001

Iron(III) spin-crossover compounds with a wide apparent thermal hysteresis around room temperature.

The magnetic properties of the spin-crossover compounds, [Fe(qsal)2]NCSe-MeOH (1) and [Fe(qsal)2]NCSe-CH2Cl2 (2), have been measured. We have discovered that both compounds 1 and 2 exhibit a wide thermal hysteresis loop of 140 K (T(1/2) upward arrow = 352 K and T(1/2) downward arrow = 212 K) and 180 K (T(1/2) upward arrow = 392 K and T(1/2) downward arrow = 212 K), respectively, in the first cycle. Thermogravimetric analysis shows that solvent molecules escape from compounds 1 and 2 around 340 and 395 K, respectively. This means that the hysteresis loops observed for the first cycle are only apparent ones. Following the first loop, they show a two-step spin-crossover in warming mode. The so-called "step 1" and "step 2" are centered around T(1/2(S1)) upward arrow = 215 K and T(1/2(S2)) upward arrow = 282 K, respectively. On the other hand, a one-step spin-crossover occurs at T(1/2) downward arrow = 212 K in cooling mode. The hysteresis widths can be estimated to be 3 K (step 1) and 70 K (step 2), assuming that the widths in steps 1 and 2 are defined as the differences between T(1/2(S1)) upward arrow and T(1/2) downward arrow, and T(1/2(S2)) upward arrow and T(1/2) downward arrow, respectively. The hysteresis width of 70 K in step 2 is one of the widest values reported so far for spin-crossover complexes. It is thought that the cooperativity operating in the complexes arises mainly from the intermolecular pi interactions between quinoline and phenyl rings. Using a previously reported model, we are able to simulate the hysteresis loop with a two-step spin-crossover in warming mode and a one-step transition in cooling mode.

Journal Article↗
PubMed2001

Extracellular signal-regulated kinase and c-Jun N-terminal protein kinase in ischemic tolerance.

The alterations and involvement of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK) activation were examined in the hippocampal CA1 region in a rat model of global brain ischemic tolerance. Western blotting study showed that ERK activation (diphosphorylation) level was decreased (3.75-, 0.56-, and 0.23-fold vs sham control) and JNK activation level was increased (3.82-, 4.63-, and 5.30-fold vs sham control) 3 days after more severe ischemic insults (6 min, 8 min, and 10 min of ischemia, respectively). These alterations were significantly prevented by pretreatment with preconditioning ischemia, which also provided neuronal protection against ischemic injury. Inhibition of ERK activation after preconditioning ischemia by PD98059, a specific ERK kinase inhibitor, significantly prevented the inhibitory effects of preconditioning ischemia on both JNK activation and ischemic injury. The results suggest that ERK activation after preconditioning ischemia may result in the prevention of JNK activation and thus be involved in the protective responses in ischemic tolerance in hippocampal CA1 region.

Animals↗
PubMed2001

Expression of bbc3, a pro-apoptotic BH3-only gene, is regulated by diverse cell death and survival signals.

BH3-only proteins function at a proximal point in a conserved cell death pathway by binding, through their BH3 domains, to other Bcl-2 family members and triggering mitochondrial events associated with apoptosis. Here, we describe a strongly pro-apoptotic BH3-only protein, designated Bbc3, whose expression increases in response to diverse apoptotic stimuli. bbc3 mRNA levels were induced by exposure to DNA-damaging agents and by wild-type p53, which mediates DNA damage-induced apoptosis. p53 transactivated bbc3 through consensus p53 binding sites within the bbc3 promoter region, indicating that bbc3 is a direct target of p53. Additionally, bbc3 mRNA was induced by p53-independent apoptotic stimuli, including dexamethasone treatment of thymocytes, and serum deprivation of tumor cells. Insulin-like growth factor-1 and epidermal growth factor, growth factors with broad anti-apoptotic activity, were each sufficient to suppress Bbc3 expression in serum-starved tumor cells. These results suggest that the transcriptional regulation of bbc3 contributes to the transduction of diverse cell death and survival signals.

Amino Acid Sequence↗
PubMed2001

Nuclear translocation of extracellular signal-regulated kinases in neuronal excitotoxicity.

Subcellular distributions of extracellular signal-kinases (ERK1/2), including their activated form (p-ERK1/2), were investigated in glutamate-induced apoptotic-like death in cultured rat cortical neurons by Western immunoblot and immunocytochemistry. During 15 min glutamate exposure, p-ERK1/2 was increased in both cytosol and nuclear extracts, but prominently so in nuclear extracts. Simultaneously, ERK1/2 were mildly decreased in cytosol (to 0.7-fold vs sham control), largely increased in nuclear extracts (to 6.2-fold vs sham control), but not changed in total cell extracts. Immunocytochemistry studies also showed a large increase in nuclear and a mild decrease in cytosol extracts of ERK1/2 at 15 min of exposure. After glutamate exposure, all the above changes reverted simultaneously. The nuclear increase of ERK1/2 was largely prevented by inhibition of ERK1/2 activation, but prolonged by elongation of ERK1/2 activation. These observations suggest that stimulation of glutamate receptors in cortical neurons may incur an activation-dependent transient nuclear translocation of ERK1/2, which might be involved in excitotoxicity through a simultaneous strong elevation of p-ERK1/2 in nucleus.

Active Transport, Cell Nucleus↗
PubMed2001

Prostate stem cell antigen is overexpressed in human transitional cell carcinoma.

Prostate stem cell antigen (PSCA), a homologue of the Ly-6/Thy-1 family of cell surface antigens, is expressed by a majority of human prostate cancers and is a promising target for prostate cancer immunotherapy. In addition to its expression in normal and malignant prostate, we recently reported that PSCA is expressed at low levels in the transitional epithelium of normal bladder. In the present study, we compared the expression of PSCA in normal and malignant urothelial tissues to assess its potential as an immunotherapeutic target in transitional cell carcinoma (TCC). Immunohistochemical analysis of PSCA protein expression was performed on tissue sections from 32 normal bladder specimens, as well as 11 cases of low-grade transitional cell dysplasia, 21 cases of carcinoma in situ (CIS), 38 superficial transitional cell tumors (STCC, stages T(a)-T(1)), 65 muscle-invasive TCCs (ITCCs, stages T(2)-T(4)), and 7 bladder cancer metastases. The level of PSCA protein expression was scored semiquantitatively by assessing both the intensity and frequency (i.e., percentage of positive tumor cells) of staining. We also examined PSCA mRNA expression in a representative sample of normal and malignant human transitional cell tissues. In normal bladder, PSCA immunostaining was weak and confined almost exclusively to the superficial umbrella cell layer. Staining in CIS and STCC was more intense and uniform than that seen in normal bladder epithelium (P < 0.001), with staining detected in 21 (100%) of 21 cases of CIS and 37 (97%) of 38 superficial tumors. PSCA protein was also detected in 42 (65%) of 65 of muscle-invasive and 4 (57%) of 7 metastatic cancers, with the highest levels of PSCA expression (i.e., moderate-strong staining in >50% of tumor cells) seen in 32% of invasive and 43% of metastatic samples. Higher levels of PSCA expression correlated with increasing tumor grade for both STCCs and ITCCs (P < 0.001). Northern blot analysis confirmed the immunohistochemical data, showing a dramatic increase in PSCA mRNA expression in two of five muscle-invasive transitional cell tumors when compared with normal samples. Confocal microscopy demonstrated that PSCA expression in TCC is confined to the cell surface. These data demonstrate that PSCA is overexpressed in a majority of human TCCs, particularly CIS and superficial tumors, and may be a useful target for bladder cancer diagnosis and therapy.

Antigens, Neoplasm↗
PubMed2001

Urea gradient size-exclusion chromatography enhanced the yield of lysozyme refolding.

Protein refolding is still a bottleneck for large-scale production of valuable proteins expressed as inclusion bodies in Escherichia coli. Usually biologically active proteins cannot be obtained with high yield at a high concentration after refolding. In order to meet the challenge of protein refolding a urea gradient gel filtration-refolding system was developed in this article. A Superdex 75 column was pre-equilibrated with a linear decreased urea gradient, the denatured protein experienced the gradual decrease in urea concentration as it went through the column. The refolding of denatured lysozyme showed this method could significantly increase the activity recovery of denatured lysozyme at high protein concentration. The activity recovery of 90% was obtained from the initial protein concentration up to 17 mg/ml within 40 min.

Chromatography, Gel↗
PubMed2001

Extracellular signal-regulated kinase 1/2 activation in hippocampus after cerebral ischemia may not interfere with postischemic cell death.

To investigate the effect of the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) on cerebral ischemic injury, temporospatial alterations of active (diphosphorylated) ERK1/2 immunoreactivity in hippocampus was examined. Western blot showed that diphosphorylated ERK1/2 were decreased at 10 min of cerebral ischemia but increased rapidly (within 2 min) and transiently (within 4 h) during reperfusion. Immunohistochemistry showed that little diphosphorylated ERK1/2 immunoreactivity was seen in CA1 pyramidal cell bodies after ischemia, while strong immunoreactivity were seen in neuronal bodies in CA3/DG and in fiber systems in both CA1 and CA3 regions. Cerebral ventricular infusion of PD98059, a specific inhibitor of ERK kinase, completely prevented ERK1/2 activation after ischemia but had no effect on the survival of pyramidal cells in CA1 subfield. The results suggest that ERK1/2 activation in hippocampus after brain ischemia may not interfere with the postischemic cell death in CA1 region.

Animals↗
PubMed2001

c-Jun N-terminal kinase activation in hippocampal CA1 region was involved in ischemic injury.

To clarify the role of c-Jun N-terminal kinase (NK) activation in brain ischemia, temporospatial alteration of active (diphosphorylated) JNK1/2 immunoreactivity in hippocampus after brain ischemia in rat was investigated. Western immunoblot study showed that JNK1/2 diphosphorylation level was increased biphasically in CA1 but not CA3/dentate gyrus (DG) after 10 min of ischemia. Cerebral ventricular infusion of JNK1/2 antisense oligonucleotides not only significantly decreased JNK1/2 protein expression and the activation level but also significantly decreased CA1 pyramidal cell death (demonstrated by cresyl violet staining) and DNA fragmentation (demonstrated by in situ end-labeling of DNA). These results suggest that JNK1/2 were selectively activated and involved in the selective cell death in hippocampal CA1 subfield after cerebral ischemia.

Animals↗
PubMed2001

PEGylated PLGA nanoparticles as protein carriers: synthesis, preparation and biodistribution in rats.

The aim of the present work was to assess the merits of PEGylated poly(lactic-co-glycolic acid) (PEG-PLGA) nanoparticles as protein and peptide drugs (PPD) carriers. PEG-PLGA copolymer, which could be used to prepare the stealth nanoparticles or long-circulating nanoparticles, was synthesized with methoxypolyethyleneglycol (MePEG) and PLGA. The structure of PEG-PLGA was confirmed with (1)H NMR and Fourier transform infrared (FTIR) spectrum, and molecular weight was determined by gel permeation chromatography (GPC). Bovine serum albumin (BSA), chosen as model protein, was encapsulated within the stealth nanoparticles with the double emulsion method. The particles were characterized in terms of size, zeta potential and in vitro release of the protein. The biological fate of the BSA-loaded nanoparticles following intravenous administration was determined over 24 h in rats. The experimental results showed that PEG-PLGA could be obtained by ring-opening polymerization of lactide and glycolide in the presence of MePEG. (1)H NMR and FTIR spectrum were consistent with the structure of PEG-PLGA copolymer. Molecular weight determined by GPC was 50800. The stealth nanoparticles loading BSA could be prepared by the double emulsion technique. The entrapment efficiency was 48.6%, particle size about 200 nm and zeta potential -16.1 mV. BSA release from the stealth nanoparticles showed an initial burst release and then sustained release. PEG-PLGA nanoparticles could extend half-life of BSA from 13.6 min of loaded in PLGA nanoparticles to 4.5 h and obviously change the protein biodistribution in rats compared with that of PLGA nanoparticles. Thus, PEG-PLGA nanoparticles could be an effective carrier for PPD delivery.

Animals↗
PubMed2001

Investigation of the electrochemical and electrocatalytic behavior of single-wall carbon nanotube film on a glassy carbon electrode.

The electrochemical behavior of a film of single-wall carbon nanotubes (SWNTs) functionalized with carboxylic acid groups was studied extensively on a glassy carbon (GC) electrode. One stable couple corresponding to the redox of the carboxylic acid group, which was supported by XPS and IR experiments, was observed. The electrode process involved four electrons, while the rate-determining step was a one-electron reduction. The SWNT film-modified electrode showed favorable electrocatalytic behavior toward the oxidation of biomolecules such as dopamine, epinephrine, and ascorbic acid.

Ascorbic Acid↗
PubMed2001

The sequence of the human genome.

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

Algorithms↗
PubMed2001

Evolutionary analyses of the human genome.

The completion of the human genome will greatly accelerate the development of a new branch of science--evolutionary genomics. We can now directly address important questions about the evolutionary history of human genes and their regulatory sequences. Computational analyses of the human genome will reveal the number of genes and repetitive elements, the extent of gene duplication and compositional heterogeneity in the human genome, and the extent of domain shuffling and domain sharing among proteins. Here we present some first glimpses of these features.

Conserved Sequence↗