Structural geochemistry of gold mineralization in the Linglong-Jiaojia district, Shandong Province, China

The Linglong-Jiaojia district is one of the most important regions containing gold deposits in China. These gold deposits can be divided into: a) the pyrite-gold-quartz vein type (Linglong type), which is controlled by brittle-ductile to ductile deformation structures, and b) the alteration-zone type (Jiaojia type), characterized by small veinlets, or the disseminated type recognized in brittle shear zones. Lode gold deposits in the Jiaojia area occur in NE brittle fracture zones, formed in a dominantly simple shear deformation regime, mainly in thrust attitude with a minor sinistral strike slip component. In the Linglong area, the lode gold deposits are located at the intersection of three types of structures: NNE and NE brittle-ductile fault zones and the ENE ductile reverse shear zone in the south of the area. The structural characteristics of these brittle shear zones are consistent with a tectonic NNW-SSE principal stress field orientation. Similar stresses explain the ENE Qixia fold axes, the Potouqing and several other ENE reverse ductile shear zones elsewhere in the region, the Tancheng-Lujiang fault zone and its subsidiaries in the vicinity of the Linglong-Jiaojia district, as well as the southern ENE suture zone north of Qingdao. Therefore these structural systems occurred as part of different major tectonic events under NNW-SSE compression principal stress fields in the area. Gold deposits are hosted in smaller-scale structures within the brittle fault zones and brittle-ductile shear zones. Although ore bodies and, on a smaller scale, quartz ore veins often seem to be randomly oriented, it is possible to explain their distribution and orientation in terms of the simple shear deformation process under which they were developed. The progressive simple shear failure is characterized by various fracture modes (tension and shear) that intervene in sequence. The tension and shear fractures are influenced by the stress level (depth of burial beneath the paleosurface) in their structural behavior, show variable dilatancy (void openings) and extend on all scales. By making use of these characteristics, a progressive failure analysis can be applied to predicting the shape and extent of ore bodies as well as the styles of mineralization at any given location.

Reversal of multidrug resistance in vincristine-resistant human gastric cancer cell line SGC7901/VCR by LY980503

AIM： To investigate the reversal effect of LY980503, a benflumetol derivative, on multidrug resistance in vincristine （VCR） -resistant human gastric carcinoma cell line SGC7901/VCR. METHODS： Cells of a human gastric cancer cell line, SGC7901, and its VCR-resistant variant, SGC7901/VCR, were cultivated with LY980503 and/or doxorubicin （DOX）. The cytotoxicity of drugs in vitro was assayed by M-IF method. Based on the flow cytometric technology, the uptake of DOX was detected in these cells by measuring DOX -associated mean fluorescence intensity （MFI）. RESULTS： SGC7901/VCR cells were 23.5 times more resistant to DOX in comparison with 5GC7901 cells. LY980503 at the concentrations of 2.0 μmol/L -10 μmol/ L had no obvious cytotoxicity to SGC7901 and SGC7901/ VCR cells. After simultaneous treatment with LY980503 at the concentrations of 2.0, 4.0 and 10 μmol/L, the ICso of DOX to SGC7901/VCR cells decreased from 1.6 ± 0.12 μmol/L to 0.55 ± 0.024, 0.25 ± 0.032 and 0.11 ± 0.015 μmol/L, respectively, thus, increasing the DOX sensitivity by 2.9-fold （P 〈 0. 05）, 6.4-fold （P 〈 0. 01） and 14.5-fold （P 〈 0. 01）, respectively. In the uptake study of DOX, simultaneous incubation of SGC7901/VCR cells with LY980503 significantly increased the DOX -associated MFI in SGC7901/VCR cells. No such results were found in parental SGC7901 cells.CONCLUSION： LY980503 at non-cytotoxic concentrations can effectively circumvent resistance of SGC7901/VCR cells to DOX by increasing intracellular DOX accumulation.

Antisense expression of PKCα improved sensitivity of SGC7901/VCR cells to doxorubicin

AIM:To explore whether antisense blocking of protein kinase C alpha(PKCα)would reverse multi-drug resistance(MDR)in the vincristine(VCR)-resistant human gastric cancer cell line SGC7901/VCR. METHODS:SGC7901/VCR cells expressing antisense PKCα,SGC7901/VCR/aPKC,were established by transfection with a recombinant plasmid reversely inserted with PKCαcDNA.Empty vector(PCI-neo)transfected cell clones,SGC7901/VCR/neo,served as the control.Western blot method was used to detect PKCαcontent in SGC7901,SGC7901/VCR,SGC7901/ VCR/neo and SGC7901/VCR/aPKC cells,using PKCα-specific antibody.The sensitivity of SGC7901,SGC7901/ VCR,SGC7901/VCR/neo and SGC7901/VCR/aPKC cells to doxorubicin(DOX)in vitro was determined by MTT assay.The uptake of DOX in these cells was detected with fluorescence spectrophotometer.RESULTS:Western blot analysis showed that the PKCαprotein level was about 8.7-fold higher in SGC7901/ VCR cells than that in SGC7901 cells,whereas the protein expression of PKCαwas reduced by 78%in SGC7901/VCR/aPKC cells when compared with the SGC7901/VCR cells.SGC7901/VCR/aPKC cells had a 4.2-fold increase in DOX cytotoxicity,accompanied by a 1.7-fold increase of DOX accumulation in comparison with SGC7901/VCR cells. CONCLUSION:PKCαpositively regulates MDR in SGC7901 cells,and inhibition of PKCαcan partially attenuate MDR in human gastric cancer cells.