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Biomedical subjects

Jing Liang

Publications and source records attributed to Jing Liang.

27 records · Page 2Linked to original sources
PubMed2004

Concentrations of hazardous heavy metals in environmental samples collected in Xiamen, China, as determined by vapor generation non-dispersive atomic fluorescence spectrometry.

Non-dispersive atomic fluorescence spectrometry (NDAFS) coupled with vapor generation (VG) sample introduction was applied to the determination of the concentrations of hazardous heavy metals, such as arsenic, cadmium, lead and mercury, in seawater, soils and total airborne particulate matter (PM) collected around the Xiamen area in China. Almost 100% sample introduction efficiency was achieved by using thiourea and ascorbic acid for the pre-reduction of As(V) to As(III), K3Fe(CN)6 and tartaric acid for pre-oxidation of Pb(II) to Pb(IV), and masking the interferences arising from the co-existing transition metals to As, Cd, Hg and Pb during their vapor generation process. Moreover, a novel sample pretreatment device was developed to avoid the loss of mercury, lead, cadmium and arsenic during sample pretreatment. With such methods, the detection limit (DL) of arsenic, cadmium, lead and mercury was down to 0.08, 0.03, 0.05, 0.01 ng mL(-1) (3sigma), respectively. The relative standard deviations (RSD, n = 11) for arsenic, cadmium, lead and mercury at 10 ng mL(-1) were 0.9%, 1.6%, 1.3% and 2.0%, respectively. The concentrations of hazardous heavy metals in the environmental samples collected in Xiamen, China are in the range from 0.02 +/- 0.001 ng mL(-1) in seawater to 15.3 +/- 0.2 microg g(-1) in soils. Besides flame/GF-AAS and ICP-AES/MS, VG-NDAFS should be another choice for the determination of hazardous heavy metals in environmental samples.

China↗
PubMed2004

Overexpression of ubiquilin decreases ubiquitination and degradation of presenilin proteins.

Mutations in presenilin proteins (PS1 and PS2) are associated with most cases of early-onset Alzheimer's disease. Several proteins appear to regulate accumulation of PS proteins in cells. One such protein is ubiquilin-1, which increases levels of coexpressed PS2 protein in a dose-dependent manner. We now report that overexpression of ubiquilin-2, which is 80% identical to ubiquilin-1, also increases the levels of coexpressed PS1 and PS2 proteins in cells. To investigate the mechanism by which ubiquilin proteins increase levels of PS proteins, we examined how overexpression of ubiquilin-1, which possesses all of the key signature motifs present in ubiquilin proteins, affects PS2 gene transcription and PS2 protein turnover and ubiquitination. HeLa cells overexpressing both PS2 and ubiquilin-1 had PS2 mRNA levels lower than HeLa cells overexpressing PS2 alone, indicating that ubiquilin-1 overexpression, in fact, decreases PS2 transcription. Cells overexpressing ubiquilin-1 and PS2 displayed decreased turnover of high molecular weight (HMwt) forms of PS2 but not of full-length PS2 proteins. The reduced turnover of HMwt PS2 proteins appears to be mediated by the binding of the ubiquitin-associated domain (UBA) of ubiquilin to ubiquitin chains conjugated onto PS2 proteins. Immunoprecipitation studies indicated that ubiquilin-1 overexpression decreases ubiquitination of coexpressed PS2 proteins, suggesting that binding of ubiquilin might block ubiquitin chain elongation. Consistent with this model, we found that the UBA domain of ubiquilin-1 binds poly-ubiquitin chains in vitro. In addition, we show that ubiquilin proteins colocalize with ubiquitin-immunoreactive structures in cells and that ubiquilin proteins are present within the inner core of aggresomes, which are structures associated with accumulation of misfolded proteins in cells. Our results suggest that ubiquilin proteins play an important role in regulating PS protein levels in cells.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Protective effects of L-arginine on reperfusion injury after pancreaticoduodenal transplantation in rats.

BACKGROUND: Post-transplantation pancreatitis and graft thrombosis are two major complications of pancreas transplantation that contribute to morbidity, mortality, and graft loss. Nitric oxide(NO) is a potent vasodilator agent formed when L-arginine (L-Arg) is converted to L-citrulline by the action of NO synthase (NOS), and plays a major role in microcirculatory changes. We therefore investigated the effect of L-Arg on reperfusion injury following pancreaticoduodenal transplantation in rats. METHODS: The homologous male Wistar rat model of heterotopic total pancreaticoduodenal transplantation was used. The L-Arg-treated rats received the intravenous injection of L-Arg 5 minutes before and after reperfusion at a dose of 200 mg/kg while the N-Nitro-L-arginine methyl ester (L-NAME)-treated rats at a dose of 10 mg/kg. The amount of NO in the pancreas graft was measured. Serum concentration of cytokine-induced neutrophil chemoattractant (CINC) was determined by enzyme-linked immunosorbant assay, the expression of CINC mRNA was detected by Northern blot assay in the pancreas graft, and the activity of myeloperoxidase (MPO) was measured. Histological examination was performed. RESULTS: The amount of NO was higher in the L-Arg group than in the control group, while it was lower in the L-NAME group than in the control group (P<0.05). The peak of serum CINC concentration occurred 3 hours after reperfusion with the difference among the groups being significant. The expression peak of CINC mRNA in the pancreas graft occurred 3 hours after reperfusion. The expression level in the L-Arg group (7.66+/-1.53 microg/L) was lower than in the control group (26.31+/-2.01 microg/L), while in the L-NAME group (34.18+/-3.12 microg/L) it was higher than that in the control group (P<0.05). The activity of MPO in the L-Arg group was obviously decreased as compared with in the other groups. The pancreas inflammation was ameliorated when L-Arg was administered, whereas the pancreas damage was aggravated when L-NAME was administered. CONCLUSIONS: L-Arg can increase the amount of NO and inhibit the elevation of CINC, the CINC mRNA expression and early neutrophil accumulation in the pancreas. NO has protective effects on ischemia/reperfusion injury in pancreaticoduodenal transplantation.

Animals↗
PubMed2004

[Influence of chemotherapy on Th1/Th2 cytokine switching in stomach cancer patients].

OBJECTIVE: To observe the influence of chemotherapy on the switching of Th1/Th2 cytokines in stomach cancer patients. METHODS: Th1/Th2 cytokine genes expressed by peripheral blood mononuclear cells of stomach cancer patients before and after chemotherapy were detected by RT-PCR. RESULTS: The expression of Th2 cytokines was dominant in patients before chemotherapy, and the dominancy became less marked after chemotherapy. CONCLUSION: The immune deviation with Th2 predominance in stomach cancer patients has a tendency to become reversed after chemotherapy.

Adenocarcinoma↗
PubMed2003

Reduced inhibition and sensitivity to neurosteroids in hippocampus of mice lacking the GABA(A) receptor delta subunit.

The delta subunit of the gamma-aminobutyric acid (A) receptor (GABA(A)R) is expressed postnatally mostly in the cerebellum, thalamus, and dentate gyrus. Previous studies in mice with a targeted disruption of the delta subunit revealed a considerable attenuation of behavioral responses to neuroactive steroids but not to other neuromodulatory drugs. Here we show that delta subunit loss leads to a concomitant reduction in hippocampal alpha4 subunit levels. These changes were accompanied by faster decay of evoked inhibitory postsynaptic potentials (IPSPs) in dentate granule neurons of -/- mutants (decay tau = 25 ms) compared with +/+ controls (tau = 50 ms). Furthermore, the GABA(A)R-mediated miniature inhibitory postsynaptic currents (mIPSCs) also decayed faster in delta-mutants (tau = 6.3 ms) than controls (tau = 7.2 ms) and had decreased frequency (controls, 10.5 Hz; mutants, 6.6 Hz). Prolongation of mIPSCs by the neuroactive steroid anesthetic, alphaxalone (1-10 microM), was smaller in delta-mutants (at 10 microM, 65% increase) compared with +/+ littermates (308% increase). In competition binding experiments, alphaxalone (0.03-1 microM) modulation of [35S]t-butylbicyclophosphorothionate binding was reduced in delta-mutant brain homogenates, indicating that the decreased alphaxalone effects on mIPSCs were due to changes in the GABA(A)R protein. Faster decay of evoked IPSPs and mIPSCs in delta-mutants suggests presence of the delta subunit at both synaptic and extrasynaptic GABA(A)Rs. Decreased synaptic and extrasynaptic inhibition likely contributes to the pro-epileptic phenotype of delta-mutants. Reduced neurosteroid sensitivity might also contribute to seizure susceptibility. While the simplest explanation is that delta subunit-containing GABA(A)Rs represent the actual target of neurosteroids, it is possible that the behavioral and physiological sensitivity to neuroactive steroids is indirectly altered in the delta -/- mice.

Anesthetics↗
PubMed2003

Withdrawal from chronic intermittent ethanol treatment changes subunit composition, reduces synaptic function, and decreases behavioral responses to positive allosteric modulators of GABAA receptors.

One of the pharmacological targets of ethanol is the GABAA receptor (GABAR), whose function and expression are altered after chronic administration of ethanol. The details of the changes differ between experimental models. In the chronic intermittent ethanol (CIE) model for alcohol dependence, rats are exposed to intermittent episodes of intoxicating ethanol and withdrawal, leading to a kindling-like state of behavioral excitability. This is accompanied by presumably causal changes in GABAR expression and physiology. The present study investigates further the effect of CIE on GABAR function and expression. CIE is validated as a model for human alcohol withdrawal syndrome (AWS) by demonstrating increased level of anxiety; diazepam improved performance in the test. In addition, CIE rats showed remarkably reduced hypnotic response to a benzodiazepine and a steroid anesthetic, reduced sensitivity to a barbiturate, but not propofol. Immunoblotting revealed decrease in alpha1 and delta expression and increase in gamma2 and alpha4 subunits in hippocampus of CIE rats, confirmed by an increase in diazepam-insensitive binding for ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo(1,5-alpha)(1,4)benzodiazepine-3-carboxylate (Ro15-4513). Elevated mRNA levels were shown for the gamma2S and gamma1 subunits. Recordings in hippocampal slices from CIE rats revealed that the decay time of GABAR-mediated miniature inhibitory postsynaptic currents (mIPSCs) in CA1 pyramidal cells was decreased, and potentiation of mIPCSs by positive modulators of GABAR was also reduced compared with control rats. However, mIPSC potentiation by the alpha4-preferring benzodiazepine ligands bretazenil and Ro15-4513 was maintained, and increased, respectively. These data suggest that specific alterations in GABAR occur after CIE and may underlie the development of hyperexcitability and ethanol dependence.

Affinity Labels↗
PubMed2003

[Digital signal acquisition and processing software for atomic fluorescence spectrometry and its application to elemental speciation].

A program was developed to collect and process digital signal by using Visual C++ for atomic fluorescence spectrometry (AFS). The software solves the data acquisition problem of coupling AFS with HPLC and other successive separation techniques. This program employs three signal processing techniques, i.e. Savitzky-Golay smoothing, Fourier filter and wavelet denoising, to smooth and filter the noisy data. The processes and comparisons of these techniques have been discussed. The program was successfully applied to the preliminary study of Cd speciation by using cation exchange HPLC coupled to AFS, and will provide a new possibility for extending the application of atomic fluorescence spectrometry to the field of elemental speciation analysis.

Cadmium↗
PubMed2002

Selection for thermodynamically stable DNA tetraloops using temperature gradient gel electrophoresis reveals four motifs: d(cGNNAg), d(cGNABg),d(cCNNGg), and d(gCNNGc).

Hairpins play important roles in the function of DNA, forming cruciforms and affecting processes such as replication and recombination. Temperature gradient gel electrophoresis (TGGE) and in vitro selection have been used to isolate thermodynamically stable DNA hairpins from a six-nucleotide random library. The TGGE-selection process was optimized such that known stable DNA tetraloops were recovered, and the selection appears to be exhaustive. In the selection, four families of exceptionally stable DNA loops were identified: d(cGNNAg), d(cGNABg), d(cCNNGg), and d(gCNNGc). (Lowercase denotes the closing base pair; N = A, C, G, or T; and B = C, G, or T.) It appears that the known stable d(cGNAg) triloop motif can be embedded into a tetraloop, with the extra nucleotide inserted into either the middle of the loop, d(cGNNAg), or at the 3'-end of the loop, d(cGNABg). For d(cGNNAg) and d(cGNABg), a CG closing base pair was strongly preferred over a GC, with DeltaDeltaG degrees (37) approximately 2 kcal/mol. Members of the two families, d(cCNNGg) and d(gCNNGc), are similar in stability. The loop sequences and closing base pairs identified for exceptionally stable DNA tetraloops show many similarities to those known for exceptionally stable RNA tetraloops. These data provide an expanded set of thermodynamic rules for the formation of tetraloops in DNA.

Base Pairing↗