Biomedical subjects
Publications and source records attributed to Q Zhang.
A series of phosphors containing Ce3+, Tb3+ ions in CaF2 and AlF3 were synthesized in a solution reaction and solid reaction method. Their excitation and emission spectra were determined. The results indicated that Ce3+ could not effectively transfer energy to Tb3+ in matrix CaF2 and AlF3 and enhance the emission of Tb3+ significantly.
With a hollow cathode lamp as exciting source, the optimum working parameters for the determination of As were selected. By adopting two hydride-generators to generate hydride and H2 simultaneously, the mechanism of AsH3 generation was studied. Experimental results show that the atomization process of AsH3 might be carried out mainly by collision with hydrogen radical.
The quantities of 21 microelements were determined in 10 Chinese traditional medicines, using both flame and graphite oven atomic absorption spectrometry. We studied the efficacies of such Chinese medicaments. The result showed the efficacies related to the inorganic microelements.
The determination of As, Hg and Mo in the composite Chinese traditional medicines such as niuhuang jiedu tablets etc. Indicates the existence of As, Hg and Mo in these medicines. The relation between these elements and the efficacy of the medicines was studied, showing that these elements play an important role in the efficacy of the drugs.
A new FAAS method for the determination of zinc and iron in maize flour using suspension sample introduction is described. The maize flour was suspended in agar sol, and injected into air-acetylene flame by using standard addition method to determine zinc and iron. The results are consistent with those obtained by ashing method. This method is convenient and rapid.
Suspension sampling technique was applied to flame atomic absorption spectrometry and was successfully used to determine calcium and magnesium in wheat flour. The wheat flour was suspended in agar sol containing dibutyl phthalate and made into suspension. Choice of suspension agent and elimination of chemical interference were studied. The test solution was injected into air-acetylene flame to determine calcium and magnesium by standard addition method. Determination results were consistent with those obtained by ashing method. The t-test showed that no difference was found between the two methods. Displacement of ashing method by suspension sampling method for the sample pretreatment is possible. This method is convenient, rapid and accurate.
The UV absorption, fluorescence, unstable spectra and quantum yields of five ternary or tetradic complexes of Eu (III) with beta-diketone (dibenzoyl methane, thenoyltrifluoroacetone), acrylic acid and other ligands were reported. The influences of the first and second ligands on absorption and luminescence spectra were found. The lifetimes and the processes of energy transfer of Eu3+ from 5D1 to 5D0 in complex solutions were measured. It was found that the lifetimes of Eu3+ complexes with TTA are approximate to each other and larger than those of complexes with DBM.
Neuronal nitric-oxide synthase (nNOS) is the primary nitric oxide (NO) regulator in neurons. The activity of the enzyme is inhibited by a protein inhibitor called PIN. We were able to purify large quantities of PIN overexpressed in bacterial cells. Analytical ultracentrifugation and chemical cross-linking studies showed that PIN exists as a monomer at low concentrations. The protein forms a high order aggregate at elevated concentrations. We have shown, using NMR spectroscopy, that the previously identified PIN-binding domain (PINB) of nNOS (residues 161-245) adopts a random coil structure in solution. By titrating 15N-labeled PINB with unlabeled PIN, the PIN-binding region of nNOS was precisely mapped to a 17-residue peptide fragment from Met-228 to His-244 of nNOS. NMR titration experiments also showed that PIN binds to nNOS with a 1:2 stoichiometry. A synthetic peptide corresponding to the identified PIN-binding region of nNOS was used to study the interaction between PIN and nNOS in detail. The functional implications of the results obtained from this study are discussed.
The synaptic basal lamina protein agrin is essential for the formation of neuromuscular junctions. Agrin mediates the postsynaptic clustering of acetylcholine receptors and regulates transcription in muscles. Agrin expression is not restricted to motor neurons but can be demonstrated throughout the CNS. The functional significance of agrin expression in neurons other than motor neurons is unknown. To test whether agrin triggers responses in neurons that lead to the activation of transcription factors, we have analyzed phosphorylation of the transcriptional regulatory site serine 133 of the transcription factor CREB (cAMP response element binding protein) in primary hippocampal neurons. Our results indicate that the neuronal (Ag4,8), but not the non-neuronal (Ag0,0), isoform of agrin induces CREB phosphorylation in hippocampal neurons. The kinetics of agrin- and BDNF-induced CREB phosphorylation are similar: peak levels are reached in minutes and are strongly reduced 2 hr later. Neuronal responses to agrin require extracellular calcium, and, in contrast to tyrosine kinase inhibitors, the specific inhibition of protein kinase A (PKA) does not affect agrin-evoked CREB phosphorylation. Our results show that hippocampal neurons specifically respond to neuronal agrin in a Ca2+-dependent manner and via the activation of tyrosine kinases.
This study investigated use of a continuous hybrid microwave heating process for producing rapid and uniform heating of cryopreserved tissues. This process combines volumetric energy deposition by microwaves with convective surface heating to produce increased warming rates. Moreover, such as a combination of heating techniques introduces additional parameters which can be varied in order to obtain better control of the heating process. In order to evaluate the effectiveness of a continuous hybrid heating scheme, a numerical simulation was developed which solved for electric and temperature fields within a microwave resonant cavity containing beef tissue. The simulation accounted for the temperature dependence of cryopreserved tissue's dielectric properties through an iterative scheme which can simulate thermal runaway. The simulation indicated that a continuous hybrid heating heating process could produce uniform warming at rates which would be unobtainable by conventional microwave heating.
The activity of an insect promoter of the cecropin B gene (Cec B) was investigated using green fluorescent protein (gfp) as a reporter in cells of channel catfish (Ictalurus punctatus). The expression vector pQZ-1 containing the Cec B promoter and a modified gfp cDNA sequence was delivered by lipofection to three catfish types: fibroblast and leukocyte cell lines, and primary cultures of leukocytes. No resistance genes were included in the vector for selection of GFP-expressing cells. The GFP mRNA was detected in all three cell types with 5 to 10 times higher concentrations observed in leukocytes than in fibroblasts. Expression was enhanced with the addition of irradiated Flavobacterium columnare (7.0 ¿10(6) cells/ml) or Escherichia coli LPS (125microgram/ml). Quantitative RT-PCR showed GFP mRNA reached maximum levels 24h after bacterial challenge in fibroblast cells, and at 10-12h after LPS challenge in fibroblasts and leukocytes. The number of fibroblasts expressing GFP increased by 0.8%, and the average of green fluorescence intensity increased by 52.8%, whereas the increase in leukocytes was 0.13% in cell number and 3.4% in fluorescence intensity. These results suggest that the transcription of the Cec B promoter in channel catfish cells exhibited an inducible pattern and could be placed under the control of the immune system (in vivo). The mechanisms for endogenous activation of the Cec B promoter and for production of gfp RNA in unchallenged cells remain to be studied.
Phagocytosis requires extension of F-actin-rich pseudopods and is accompanied by membrane fusion events. Members of the ARF family of GTPases are essential for many aspects of membrane trafficking. To test a role for this family of proteins in Fcgamma receptor-mediated phagocytosis, we utilized the fungal metabolite brefeldin A (BFA). The addition of 100 microM BFA to a subclone of RAW 264.7 macrophages disrupted the appearance and function of the Golgi apparatus as indicated by altered immunofluorescent distribution of beta-COP and reduced efflux of BODIPY C5-ceramide, a phospholipid that normally accumulates in the Golgi apparatus. In contrast, BFA had no effect on phagocytosis of IgG-coated erythrocytes. These results suggested that activation of BFA-sensitive ARFs is not required for phagocytosis. ARF6 is unique among members of the ARF family in that its membrane association is unaffected by BFA. Expression of ARF6 mutants defective in either GTP hydrolysis (Q67L) or binding (T27N) inhibited phagocytosis of IgG-coated erythrocytes and attenuated the focal accumulation of F-actin beneath the test particles. These results indicate a requirement for ARF6 in Fcgamma receptor-mediated phagocytosis and suggest that ARF6 is an important mediator of cytoskeletal alterations after Fcgamma receptor activation.
BACKGROUND: Despite intense investigation, the effector of the infarct-limiting protection observed during the late phase of ischemic preconditioning (PC) remains unknown. The goal of this study was to test the hypothesis that late PC against myocardial infarction is mediated by the activity of nitric oxide synthase (NOS). METHODS AND RESULTS: Conscious rabbits underwent a 30-minute coronary occlusion followed by 3 days of reperfusion. In group I (control group, n= 10), infarct size (tetrazolium staining) averaged 56.8+/-5.3% of the risk region, which was decreased to 27.6+/-2.5% (P<0.05) in rabbits preconditioned 24 hours earlier with a sequence of six 4-minute occlusion/4-minute reperfusion cycles (group II, n= 10). When preconditioned rabbits were given the nonselective NOS inhibitor N(omega)-nitro-L-arginine (L-NA, 13 mg/kg i.v. [group III, n=8]) or the selective iNOS inhibitor aminoguanidine (AG, 150 mg/kg SC [group V, n=7]) before the 30-minute occlusion, the protective effect of late PC was completely abrogated; that is, infarct size (59.9+/-4.5% and 65.8+/-3.3%, respectively) was similar to that measured in the control group. Measurements of systolic wall thickening (sonomicrometry) demonstrated that L-NA and AG also abolished the improved recovery of myocardial function effected by late PC in group II. When rabbits were given L-NA or AG without prior PC (group IV [n=8] and group VI [n=6], respectively), infarct size did not differ from that observed in controls (53.8+/-4.3% and 59.8+/-4.3%, respectively), demonstrating that L-NA and AG do not increase the extent of cell death in nonpreconditioned myocardium. CONCLUSIONS: Taken together, these results indicate that in the conscious rabbit, the infarct-sparing effect of the late phase of ischemic PC is mediated by the activity of NOS and suggest that the specific isoform primarily responsible for this cardioprotective phenomenon is iNOS. Thus, NO appears to be a pivotal component of the pathophysiological cascade of late PC.
Photoreceptor dysplasia (pd) is an autosomal recessive disease of miniature schnauzer dogs causing retinal degeneration. The disease is a homologue of retinitis pigmentosa, a group of genetically heterogeneous diseases, causing blindness in humans. A subtraction library was prepared from retinas of pd affected and age-matched normal control dogs to isolate de novo candidate genes for further examination. From the subtraction library, cDNA for phosducin (PDC), a member of the phototransduction pathway, was isolated as a transcript expressed at a higher level in the affected retina. First, the normal canine PDC cDNA was characterized to evaluate the PDC gene in the pd-affected retina. The characterized region of normal PDC cDNA spans 1258 nucleotides (nt) that include 738 nt of coding sequence predicted to encode a protein (Mr=28 209) of 245 amino acids (aa). Over the coding region, PDC shares 86-95% nt sequence identity and 90-95% identity in the deduced aa sequence with homologous mammalian sequences. A major transcript (1.9 kb) was observed only in retina by Northern analysis, but low levels of transcript were detected in brain, liver and kidney by reverse transcription and polymerase chain reaction. Retinal immunocytochemistry showed that PDC was detected only in rod photoreceptors, mainly in the inner segment and perinuclear region. By Northern blot analysis, increased PDC expression was observed in pre-degenerate affected retina relative to the age-matched normal. In pd- affected miniature schnauzer pedigree, a missense mutation was detected in codon 82 (CGA to GGA) that would create a non-conservative substitution (Arg to Gly) in close vicinity to the residue (Glu 85) which directly interacts with the betagamma-subunits of transducin. Only pd-affected dogs were found to be homozygous for the mutant allele, and none among 48 dogs tested from 20 other dog breeds had this allele, suggesting that the mutation could be causally associated with pd in miniature schnauzers. However, since some affected dogs are heterozygous for the mutant allele, and some are homozygous for the wild-type allele, this putative PDC missense mutation, if it is indeed a disease causing mutation, does not account entirely for the genetics of inherited retinal degeneration in the miniature schnauzer breed.
Deficiency of blood coagulation factor V or tissue factor causes the death of mouse embryos by 10.5 days of gestation, suggesting that part of the blood coagulation system is necessary for development. This function is proposed to require either generation of the serine protease thrombin and cell signaling through protease-activated receptors or an activity of tissue factor that is distinct from blood clotting. We find that murine deficiency of prothrombin clotting factor 2 (Cf2) was associated with the death of approximately 50% of Cf2(-/-) embryos by embryonic day 10.5 (E10.5), and surviving embryos had characteristic defects in yolk sac vasculature. Most of the remaining Cf2(-/-) embryos died by E15.5, but those surviving to E18.5 appeared normal. The rare Cf2(-/-) neonates died of hemorrhage on the first postnatal day. These studies suggest that a part of the blood coagulation system is adapted to perform a developmental function. Other mouse models show that the absence of platelets or of fibrinogen does not cause fetal wastage. Therefore, the role of thrombin in development may be independent of its effects on blood coagulation and instead may involve signal transduction on cells other than platelets.
The present study examined whether modified xenobiotic transport, resulting from chlordecone (CD) or dieldrin pretreatment, would alter polycyclic aromatic hydrocarbon (PAH) or organochlorine (OC) target organ doses and subsequent tumor organospecificity or incidence rates in rainbow trout. Additionally, the potential for exposure to dieldrin or CD, following PAH exposure, to enhance tumor incidence was assessed. Evaluation of CD pretreatment effects on [14C]CD disposition in trout was conducted following two i.p. (0-15 mg/kg) and two dietary (0-0.4 mg/kg/d) pretreatment regimes. To assess the influence of OC pretreatment on cancer induced by the PAH 7,12-dimethylbenz[a]anthracene (DMBA), juvenile trout were fed control, CD (0.1, 0.4 mg/kg/d), or dieldrin (0.1, 0.3 mg/kg/d) diets for 9 wk, received a waterborne [3H]DMBA exposure (1 mg/L, 20 h), and resumed control, CD, or dieldrin diets for 33 wk. [3H]DMBA disposition and hepatic [3H]DMBA binding were examined immediately and 24 h after exposure. Hepatic and stomach tumor incidences were determined 33 wk after DMBA exposure. CD pretreatment did not influence [14C]CD or [3H]DMBA hepatic concentrations, hepatic [3H]DMBA DNA binding, or hepatic/stomach tumor incidence. It did, however, elevate bile [14C]CD and [3H]DMBA concentrations. Postinitiation exposure to CD weakly enhanced DMBA-induced hepatic tumor incidence at the low but not the high CD dose. Dieldrin pretreatment did not influence stomach [3H]DMBA equivalents or stomach tumor incidence but did cause an elevation in biliary and hepatic concentrations of [3H]DMBA equivalents. [3H]DMBA binding to liver DNA was significantly increased and hepatic tumor incidence was elevated by dieldrin pretreatment. Dieldrin treatment following DMBA initiation did not enhance hepatic or stomach tumor incidence. Ecoepidemiology studies, to date, have reported correlations between the co-occurrence of PAHs and OCs and elevated tumor incidence in feral fish, but cause-and-effect relationships have been difficult to establish. The results of the present study confirm that OCs, such as dieldrin and CD, play a role in modifying PAH-induced carcinogenesis in fish.
beta1A integrin subunits with point mutations of the cytoplasmic domain were expressed in fibroblasts derived from beta1-null stem cells. beta1A in which one or both of the tyrosines of the two NPXY motifs (Y783, Y795) were changed to phenylalanines formed active alpha5 beta1 and alpha6 beta1 integrins that mediated cell adhesion and supported assembly of fibronectin. Mutation of the proline in either motif (P781, P793) to an alanine or of a threonine in the inter-motif sequence (T788) to a proline resulted in poorly expressed, inactive beta1A. Y783,795F cells developed numerous fine focal contacts and exhibited motility on a surface. When compared with cells expressing wild-type beta1A or beta1A with the D759A activating mutation of a conserved membrane-proximal aspartate, Y783, 795F cells had impaired ability to transverse filters in chemotaxis assays. Analysis of cells expressing beta1A with single Tyr to Phe substitutions indicated that both Y783 and Y795 are important for directed migration. Actin-containing microfilaments of Y783,795F cells were shorter and more peripheral than microfilaments of cells expressing wild-type beta1A. These results indicate that change of the phenol side chains in the NPXY motifs to phenyl groups (which cannot be phosphorylated) has major effects on the organization of focal contacts and cytoskeleton and on directed cell motility.
OBJECTIVE: To explore a scheme of using PCR analysis in the detection of carriers of Hind III polymorphism of factor VIII gene of hemophilia A. METHODS: Implicating intron 19 of the factor VIII gene of 6 patients with the hemophilia A and 207 unrelated X-chromosomes were amplified by PCR and were analysed by means of Amp-RFLPs of Hind III. RESULTS: The incidence of the polymorphic Hind III sites in the given population was found to be 0.29. The frequence of the Hind III heterozygotes in women calculated according to Hardy-Weinberg equation was 0.41, which proved to be informative enough for carrier detection and prenatal diagnosis of hemophilia A. 2 out of 6 families (33%)examined in this study were informative. CONCLUSION: The new scheme proved to be effective for hemophilia A carrier detection and prenatal diagnosis.