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Biomedical subjects

Qiang Lu

Publications and source records attributed to Qiang Lu.

32 records · Page 2Linked to original sources
PubMed2004

Validation of an atomic absorption rubidium ion efflux assay for KCNQ/M-channels using the ion Channel Reader 8000.

M-channels (M-current), encoded by KCNQ2/3 K(+) channel genes, have emerged as novel drug targets for a number of neurological disorders. The lack of direct high throughput assays combined with the low throughput of conventional electrophysiology (EP) has impeded rapid screening and evaluation of K(+)-channel modulators. Development of a sensitive and efficient assay for the direct measurement of M-current activity is critical for identifying novel M-channel modulators and subsequent investigation of their therapeutic potential. Using a stable CHO cell line expressing rat KCNQ2/3 K(+) channels confirmed by EP, we have developed and validated a nonradioactive rubidium (Rb(+)) efflux assay in a 96-well plate format. The Rb(+) efflux assay directly measures the activity of functional channels by atomic absorption spectroscopy using the automated Ion Channel Reader (ICR) 8000. The stimulated Rb(+) efflux from KCNQ2/3-expressing cells was blocked by the channel blockers XE991 and linopirdine with IC(50) values of 0.15 microM and 1.3 microM, respectively. Twelve compounds identified as KCNQ2/3 openers were further assessed in this assay, and their EC(50) values were compared with those obtained with EP. A higher positive correlation coefficient between these two assays (r = 0.60) was observed than that between FlexStation membrane potential and EP assays (r = 0.23). To simplify the assay and increase the throughput, we demonstrate that EC(50) values obtained by measuring Rb(+) levels in the supernatant are as robust and consistent as those obtained from the ratio of Rb(+) in supernatant/lysate. By measuring the supernatant only, the throughput of ICR8000 in an eight-point titration is estimated to be 40 compounds per day, which is suitable for a secondary confirmation assay.

Animals↗
PubMed2004

[Immunoscreening of newborn larvae cDNA library of Trichinella spiralis].

OBJECTIVE: To obtain antigenic genes encoding newborn larvae antigens of Trichinella spiralis. METHODS: Newborn larvae (NBL) cDNA library of Trichinella spiralis was screened using the infected swine serum and positive clones were sequenced and analysed. RESULTS: 158 positive clones were obtained from 4.5 x 10(5) recombinant clones by immunoscreening. The sequence analysis of positive clones showed that there are 36 novel cDNAs, 5 reported cDNAs and 12 cDNAs without the ORF showing high similarity to the mitochondrial DNA of Trichinella spiralis. CONCLUSION: Some cDNAs encoding antigenic protein of newborn larvae of Trichinella spiralis were obtained.

Amino Acid Sequence↗
PubMed2003

Synthesis and hydrolysis of a phenylalanyl adenylate pentacoordinated phosphorane.

Amino acid-nucleotide conjugates have important biological functions and therapeutic applications. For example, aminoacyl adenylates are key intermediates in aminoacyl tRNA synthetase reactions. They may also be involved in the prebiotic synthesis of polypeptides. Finally, various amino acid carbomethoxy aryl phosphoramidates of nucleotide prodrugs may be activated through a mechanism involving a pentacoordinated phosphorane intermediates. In order to understand better the chemistry of these compounds, a phenylalanyl adenylate pentacoodinated phosphorane has been synthesized in 72% yield and its decomposition in aqueous solution studied. Hydrolysis gave 2('),3(')-O-isopropylidene adenosine 5(')-monophosphate, 2('),3(')-O-isopropylidene adenosine, and phenylalanine. The results provide model chemistry for the enzymatic degradation mechanism of antiviral aryl amino acid phosphodiester amidates in cells, which leads to their activation.

Adenosine Monophosphate↗
PubMed2003

c-Jun expression in surviving and regenerating retinal ganglion cells: effects of intravitreal neurotrophic supply.

PURPOSE: To investigate c-jun expression in surviving and axon-regenerating retinal ganglion cells (RGCs) and the effect of intravitreal neurotrophic supply on c-jun expression. METHODS: All animals underwent optic nerve transection (ONT) 0.5 mm behind the eyeball. Some animals underwent a replacement of the optic nerve with an autologous sciatic nerve graft (SNG) to allow axonal regrowth. To provide a neurotrophic supply, a peripheral nerve (PN) segment or brain-derived neurotrophic factor (BDNF)/ciliary neurotrophic factor (CNTF) was applied intravitreally. The time course of c-jun expression was first examined in both surviving and regenerating RGCs. Then, c-jun expression was examined in surviving and regenerating RGCs 3 weeks after intravitreal BDNF/CNTF treatment. Animals with vehicle eye injection were used as the control. Fluorescent dye was used for retrograde labeling of surviving (applied behind the eyeball) and regenerating (applied at the distal end of the SNG) RGCs. All retinas were immunohistochemically stained for c-jun. RESULTS: c-Jun was not detected in normal RGCs, but weak expression was seen in surviving RGCs after ON injury. The proportion of c-jun-positive (+) RGCs among surviving cell population was 52.6% to 86.5% 2 to 6 weeks after ONT. Among regenerating RGCs, more than 80% expressed c-jun in all treatment groups, a proportion that was significantly higher after CNTF treatment (90.7%). In addition, c-jun expression was much stronger in intensity and the c-jun(+) nuclei were much larger in regenerating than in surviving RGCs. CONCLUSIONS: c-Jun expression in RGCs was upregulated after injury. Most regenerating RGCs were c-jun(+), and the intensity of c-jun expression was higher in regenerating than in surviving RGCs. CNTF also upregulated c-jun expression in RGCs.

Animals↗
PubMed2003

[The effect of the period of cryopreservative storage on the cryosurvival of human spermatozoa].

OBJECTIVES: To study the effect of cryopreservative period on the cryosurvival of human spermatozoa and find out the optimal recovery time of cryopreservation. METHODS: Eighty-eight semen samples were collected from normal donors and divided randomly into 5 groups according to the period of cryopreservative storage (1 d, 7 d, 30 d, 180 d, 300 d) in liquid nitrogen after being frozen by the programized, three-step freezing method. Fresh and frozen-thawed semen were examined by the routine analysis of semen and then the sperm recovery rate were calculated. RESULTS: There were no significant differences in sperm recovery rate between group I and the others (P > 0.05). The period of cryopreservative storage in liquid nitrogen had no correlation with the cryosurvival of human spermatozoa (r = 0.05, P > 0.05). CONCLUSIONS: It was indicated that freezing-thawing after 24 h would be helpful to the screening of semen donors in batches for donor insemination of human sperm bank.

Cryopreservation↗
PubMed2003

[Cloning and sequence analysis of a novel stage-specific cDNA from adult Trichinella spiralis].

OBJECTIVE: To clone a stage-specific novel cDNA from 5 day-old adult worm (AD5) of Trichinella spiralis. METHODS: The cDNA library of AD5 was screened by an AD5 stage-specific cDNA probe labeled with digoxigenin (DIG). The positive clones were sequenced and analysed. RESULTS: The positive clone contained a cDNA insert of 1,132 bp in length with a full length open reading frame (ORF) of 1,032 bp. The cDNA encoded a polypeptide of 343 amino acid residues(aa) with a molecular weight of 35.1 kDa and an isoelectric point (IP) of 4.8. InterProScan analysis showed that the 117-120 aa (SGYG) was a glycosaminoglycan attachment site, 27-86 aa was nematode cuticle collagen N-terminal domain and 153-228 aa was collagen repeat (G-x-y) domain. Signal PV2.0 analysis indicated that the region of 1-43 aa was a signal peptide. Blastn homology analysis in Genbank revealed that the cDNA had no obvious homology to any other known gene sequence. Blastn analysis revealed high homology to cuticle collagen with identities more than 40%. CONCLUSION: A novel AD5 stage-specific cDNA encoding a full length ORF was cloned and sequence analysis showed this gene encoded cuticle collagen of Trichinella spiralis.

Amino Acid Sequence↗
PubMed2002

Probe size effects on the microrheology of associating polymer solutions.

Diffusing wave spectroscopy has been used to investigate the thermally driven displacement of colloidal particles dispersed in solutions of associating polymers (APs). The effect of varying colloidal probe size on the measured particle displacements is studied in particular. Recent theories of microrheology are examined in light of the observed effects. The associating polymer used in this research was a linear polyethylene oxide (PEO) chain (molecular weight 35 000 g/mole) with a Cl14 aliphatic group appended to each end of the PEO. Above a critical concentration, the associating polymers display linear viscoelasticity consistent with the Maxwell model. The concentration of aqueous AP solutions was varied from 0.25 to 4.0 wt. %. At low concentration of APs, the mean square displacement of the colloidal beads was indistinguishable from simple Brownian diffusion in the aqueous solvent. However, at concentrations greater than 0.5 wt. %, the mean square displacement differed from simple diffusion in a way that was found to be consistent with the Maxwell model linear viscoelasticity (LVE) of the AP solutions. Significantly, for the most concentrated solutions, as the probe particle size was varied from 0.3 to 2.2 microm, the observed mean square displacement deviated substantially from the generalized Stokes-Einstein behavior predicted by microrheological theories. Our experiments showed that these deviations could not be attributed to specific physicochemical interactions at the probe-matrix interface, since observed mean square displacements were independent of different probe surface chemistries studied. Moreover, this particle size effect was not observed in semidilute, high molecular weight PEO solutions (molecular weight 4.0 x 10(6) g/mole). We concluded that possible effects of AP network compressibility and AP depletion at the probe surface could not account for the observed particle size effects. We examined recent reports of the structural heterogeneity in AP solutions for their possible connection to our observation of the breakdown of the generalized Stokes-Einstein equation for this system. Numerical conversion of the microscopic results to the linear viscoelastic moduli, G'(omega) and G"(omega), by means of a constrained regularization method (CONTIN), demonstrates that the experiments with larger probe particles are most consistent with the single-mode Maxwell model LVE observed by macroscopic mechanical rheology.

Journal Article↗
PubMed2002

Unique isoform of Galpha -interacting protein (RGS-GAIP) selectively discriminates between two Go-mediated pathways that inhibit Ca2+ channels.

Regulators of G-protein signaling (RGS) proteins constitute a large family of GTPase-activating proteins for heterotrimeric G proteins. More than 20 RGS genes have been identified in mammals. One of these, the Galpha-interacting protein (GAIP), preferentially interacts with members of the G(i)/G(o) subfamily of G proteins in mammalian cells, but its selectivity among members of this subfamily in vitro is limited. Here we report the cloning and functional characterization of a unique cDNA isoform of GAIP, derived from embryonic chicken dorsal root ganglion neurons. Chick GAIP is composed of 199 amino acids, organized into a conserved RGS domain (85% identical to human GAIP), and a unique, short N terminus (only 41% identical, 50% homologous to known mammalian orthologues). Consistent with this unique primary structure, chick GAIP has physiological properties that distinguish it from mammalian GAIPs. We have explored the selectivity of chick GAIP in electrophysiological assays of two G(o)-mediated forms of Ca(2+) channel inhibition produced by gamma-aminobutyric acid in chick dorsal root ganglion neurons, voltage-independent inhibition (mediated by G(o)alpha) and voltage-dependent inhibition (mediated by G(o)betagamma). Dialyzing recombinant chick GAIP in these cells selectively reduced voltage-independent inhibition without affecting voltage-dependent inhibition. Mammalian GAIP, tested under identical conditions in previous studies, demonstrated no selectivity between these two inhibitory processes; thus, our results suggest that the functional specificity of chick GAIP is likely to be determined by its unique N terminus.

Amino Acid Sequence↗
PubMed2002

Axonal protein synthesis provides a mechanism for localized regulation at an intermediate target.

As axons grow past intermediate targets, they change their responsiveness to guidance cues. Local upregulation of receptor expression is involved, but the mechanisms for this are not clear. Here protein synthesis is traced within individual axons by introducing RNAs encoding visualizable reporters. Individual severed axons and growth cones can translate proteins and also export them to the cell surface. As axons reach the spinal cord midline, EphA2 is among the receptors upregulated on at least some distal axon segments. Midline reporter upregulation is recapitulated by part of the EphA2 mRNA 3' untranslated region, which is highly conserved and includes known translational control sequences. These results show axons contain all the machinery for protein translation and cell surface expression, and they reveal a potentially general and flexible RNA-based mechanism for regulation localized within a subregion of the axon.

3' Untranslated Regions↗
PubMed2002

[Mitochondrial myopathy and mitochondrial encephalomyopathy].

OBJECTIVE: To investigate the symptomatic, biochemical, and pathological characteristics of mitochondrial myopathy and mitochondrial encephalomyopathy. METHODS: Physical examination, electromyography, electroencephalography, cranial CT or MRI, serum enzymological examination, and light microscopy and electron microscopy of muscle biopsy specimens were made among twenty-one in-patients with the diagnosis of mitochondrial myopathy and mitochondrial encephalopathy. All the patients were followed up for more than 5 years. RESULTS: Four patients died of lung infection, epilepticism or multiple organ failure 3, 4, 6, and 8 years after the onset of disease. One patient had already survived for 12 years. Among the 6 patients with the original diagnosis of mitochondrial myopathy, the diagnosis of two was changed as myoclonus epilepsy with ragged fiber (MERRF) 5 and 6 years after the onset. Among the seven patients whose disease was originally diagnosed as chronic progressive external ophthalmoplegia the diagnosis was changed as mitochondrial encephalomyopathy with lactic acidemia and stroke like episodes seven years after the onset. CONCLUSION: It is not difficult to diagnose mitochondrial myopathy and mitochondrial encephalomyopathy based on the symptomatical, biochemical, and pathological characteristics. However, the clinical manifestations of these diseases may change during the progress of the disease. Follow-up is highly recommended.

Adolescent↗
PubMed2002

Enhanced survival and regeneration of axotomized retinal ganglion cells by a mixture of herbal extracts.

The aim of this study is to investigate the effects of Panax quinquefolius L. extract (PQE), Ginkgo biloba extract (GBE), and Hypericum perforatum extract (HPE), in combination or alone, on the survival and regeneration of axotomized retinal ganglion cells (RGCs) in an optic nerve transection model in adult hamsters. Unilateral transection of the optic nerve was performed to evaluate the effects of herbal extracts on the survival of axotomized RGCs. Effects of the herbal extracts on axonal regeneration of axotomized RGCs, on the other hand, were studied by attaching a peripheral nerve graft onto the transected ocular stump to induce regeneration. Operated animals received daily oral administration of vehicle or herbal extracts (PQE, GBE, and HPE), alone or in combination, for 7 and 21 days, respectively, in the survival and regeneration experiments. Surviving and regenerating RGCs were retrogradely labeled with Fluoro-Gold. The eyes were then enucleated and the retinas were flat-mounted for the counting of the labeled RGCs. Treatment with PQE, GBE and HPE alone failed to offer neuroprotection to injured RGCs. However, treatment with Menta-FX, a mixture of PQE, GBE, and HPE, significantly augmented RGC survival 7 days postaxotomy. Treatment with Menta-FX also induced a significant (87%) increase in the number of regenerating RGCs 21 days after optic nerve transection. This study demonstrates that herbs can act as a potential neuroprotective agent for damaged RGCs. It also suggests that the therapeutic value of herbal remedies can be maximized by the use of mixtures of appropriate herbs.

Animals↗
PubMedDate not supplied

Functional census of mutation sequence spaces: the example of p53 cancer rescue mutants.

Many biomedical problems relate to mutant functional properties across a sequence space of interest, e.g., flu, cancer, and HIV. Detailed knowledge of mutant properties and function improves medical treatment and prevention. A functional census of p53 cancer rescue mutants would aid the search for cancer treatments from p53 mutant rescue. We devised a general methodology for conducting a functional census of a mutation sequence space by choosing informative mutants early. The methodology was tested in a double-blind predictive test on the functional rescue property of 71 novel putative p53 cancer rescue mutants iteratively predicted in sets of three (24 iterations). The first double-blind 15-point moving accuracy was 47 percent and the last was 86 percent; r = 0.01 before an epiphanic 16th iteration and r = 0.92 afterward. Useful mutants were chosen early (overall r = 0.80). Code and data are freely available (http://www.igb.uci.edu/research/research.html, corresponding authors: R.H.L. for computation and R.K.B. for biology).

Artificial Intelligence↗