Zhi Luo

Bio: Zhi Luo is an academic researcher from Huazhong Agricultural University. The author has contributed to research in topics: Lipid metabolism & Catfish. The author has an hindex of 31, co-authored 152 publications receiving 3028 citations. Previous affiliations of Zhi Luo include Chinese Academy of Fishery Sciences & Hunan University of Arts and Science.

Toxicity of Ag, CuO and ZnO nanoparticles to selected environmentally relevant test organisms and mammalian cells in vitro: a critical review

Abstract: Nanoparticles (NPs) of copper oxide (CuO), zinc oxide (ZnO) and especially nanosilver are intentionally used to fight the undesirable growth of bacteria, fungi and algae. Release of these NPs from consumer and household products into waste streams and further into the environment may, however, pose threat to the ‘non-target’ organisms, such as natural microbes and aquatic organisms. This review summarizes the recent research on (eco)toxicity of silver (Ag), CuO and ZnO NPs. Organism-wise it focuses on key test species used for the analysis of ecotoxicological hazard. For comparison, the toxic effects of studied NPs toward mammalian cells in vitro were addressed. Altogether 317 L(E)C50 or minimal inhibitory concentrations (MIC) values were obtained for algae, crustaceans, fish, bacteria, yeast, nematodes, protozoa and mammalian cell lines. As a rule, crustaceans, algae and fish proved most sensitive to the studied NPs. The median L(E)C50 values of Ag NPs, CuO NPs and ZnO NPs (mg/L) were 0.01, 2.1 and 2.3 for crustaceans; 0.36, 2.8 and 0.08 for algae; and 1.36, 100 and 3.0 for fish, respectively. Surprisingly, the NPs were less toxic to bacteria than to aquatic organisms: the median MIC values for bacteria were 7.1, 200 and 500 mg/L for Ag, CuO and ZnO NPs, respectively. In comparison, the respective median L(E)C50 values for mammalian cells were 11.3, 25 and 43 mg/L. Thus, the toxic range of all the three metal-containing NPs to target- and non-target organisms overlaps, indicating that the leaching of biocidal NPs from consumer products should be addressed.

MicroRNAs: Target Recognition and Regulatory Functions

Abstract: MicroRNAs (miRNAs) are endogenous ∼23 nt RNAs that play important gene-regulatory roles in animals and plants by pairing to the mRNAs of protein-coding genes to direct their posttranscriptional repression. This review outlines the current understanding of miRNA target recognition in animals and discusses the widespread impact of miRNAs on both the expression and evolution of protein-coding genes.

Cell-surface receptors forgibbon apeleukemia virus and amphotropic murineretrovirus areinducible sodium-dependent phosphate symporters

Abstract: Cell surface receptors forgibbon apeleuke- miavirus (Glvr-1) andmarine amphotropic retrovirus (Ram-i) aredistinct butrelated proteins having multiple membrane- nning regions. Distant homology with aputative phosphate permease ofNeurospora crussa suggested that these receptors might serve transport functions. Byexpression inXenopus laevis oocytes andinmam l cells, wehaveidentified Glvr-1 andRam-iassodium-dependent phosphate symport- ers. Two-electrode voltage-camp analysis indicates netcation influx, gestngthatphosphate istransported withexcess sodium ions. Phosphate uptake wasreduced by>50%in mousefibroblasts expressing amphotropic envelope glycopro- tein, which binds toRam-i, indicating that Ram-iIsamajor phosphate transporter inthese cells. RNAanalysis shows wide butdistinct tissue distributions, withGlvr-1 expression being highest inbonemarrowandRam-i inheart. Overexpression of Ram-i severely reprsdGlvr-i synthesis infibroblasts, sug- gesting that transporter expression maybecontrolled bynet phosphate accumulation. Accordingly, depletion ofextracellu- larphosphate increased Ram-iandGlvr-i expression 3-to 5-fold. Theseresults suggest simple methods tomodulate retroviral receptor expression, withpossible applications to humangenetherapy. Keyissues invirology havebeenidentification ofcell-surface virus receptors, determination ofreceptor expression pat- terns, andelucidation oftheeffects ofinfection onthenormal functions ofthese molecules. Theseissues arecritical inthe caseofretroviruses because cells canbecomechronically infected, leading toreceptor down-modulation andsubse- quentderangements incellular functions. Forexample, the CD4receptor forhumanimmunodeficiency virus (HIV) is important forhelper T-cell function, andinterference with this normal function isanimportant aspect ofHIV-induced disease (1). Indeed, three genes ofHIV(env, nef, andvpu) caneachmediate CD4down-modulation (1-4). Whileseveral retroviral receptor cDNAshavebeeniso- lated (5-11), theonly functionally characterized receptors are theabove-mentioned CD4forHIVandasodium-indepen- dentcationic aminoacidtransporter forecotropic murine leukemia viruses (MLVs)(12, 13). Amongthecloned recep- tors with unknown functions arethose that mediate infections ofgibbon apeleukemia virus (GALV)andofmouseampho- tropic retrovirus (these receptors aretermed Glvr-1 and Ram-1,respectively) (7,10,11). Glvr-1 andRam-1are distinct proteins withmultiple hydrophobic potential mem- brane-spanning sequences. Although theycontain large un- related central domains, theyshare about60%overall se- quence identity andhaveabout 25%identity withaputative phosphate permease ofNeurospora crassa (10, 11,14,15). These data suggested that Glvr-1 andRam-1might betrans- porters; however, their solute specificities couldnotbe inferred because evenclosely related transport proteins often carry unrelated solutes (12, 13,16,17). Weidentified thetransporter activities ofGlvr-i andRam-1 byasystematic approach that involved expression ofthese proteins inXenopus laevis oocytes andmeasurement of transmembrane currents during exposure oftheoocytes to different salts andnutrients. Ourresults indicate that Glvr-1 andRam-1aresodium/phosphate symporters andthat these proteins provide amajor pathway forphosphate uptake into manymammalian cells. Inaddition, wehaveshownthat phosphate transport rates areaffected bothbyretroviral infection andbychanges inextracellular phosphate levels. MATERIALSANDMETHODS Cell Lines andRetroviral Vectors. Cell lines usedincluded 208Fratembryo fibroblasts (18), PA317cells (19), andNIH 3T3thymidine kinase-minus mouseembryo fibroblasts (20) andderivatives. Cells weregrowninDulbecco's minimal essential mediumwith10%o (vol/vol) fetal bovine serum. Retroviral vectors encoding neomycin phosphotransferase andratRam-1, humanGlvr-1, themouseecotropic receptor Rec-i, orhumanclotting factor IXweremadebycloning the respective cDNAsinto theretroviral vector LXSN(21). Vectors weretransfected into PA317retrovirus packaging cells (19), andtransiently produced virus washarvested after 2daysandwasusedtotransduce 208Fratfibroblasts as described (21) except fortheclotting factor IXvirus, which washarvested fromapreviously described stable vector- producing cell line (22). Transduced cells weregrowninthe presence ofG418toselect forcells expressing thevectors. Ion-Transport Assays inXenopus Oocytes Injected with Retrovirus Receptor RNAs.Thecoding regions oftherat Ram-i (10) andhumanGlvr-1 (7)cDNAswerecloned into pGEM-7Z(Promega) withtheir 5'endsadjacent totheSP6 promoter. FormRNA synthesis, theplasmids werelinear- ized andtranscribed withSP6polymerase inthepresence of m7G(5')ppp(5')G capsaccording tothemanufacturer's direc- tions (Pharmacia). Xenopus laevis oocytes wereinjected with 50nlofmRNA (1ng/nl) orwith anequal volume ofH20and wereincubated for4-6daysat17'C; thentwo-microelec- trode voltage-clamp recordings orradiolabel uptake assays