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Showing papers by "Chinese Academy of Sciences published in 1997"


Journal ArticleDOI
TL;DR: In this article, the electrochemical behavior of magnesium was studied in representative chloride and sulphate solutions including NaCl, Na2SO4, NaOH and their mixed solutions, HCl, and H2SO 4: (1) by measuring electrochemical polarisation curves, (2) by using electrochemical impedance spectroscopy (EIS), and (3) by simultaneous measurement of hydrogen gas evolution and measurement of magnesium dissolution rates using ICPEAS.

757 citations



Journal ArticleDOI
TL;DR: In this article, the authors evaluate the integrative effects of water management and fertiliser application for mitigating greenhouse gas emissions in order to attenuate the greenhouse effect contributed by rice paddy fields.
Abstract: Methane and N2O emissions affected by nitrogen fertilisers were measured simultaneously in rice paddy fields under intermittent irrigation in 1994. Ammonium sulphate and urea were applied at rates of 0 (control), 100 and 300 kg N ha-1. The results showed that CH4 emission, on the average, decreased by 42 and 60% in the ammonium sulphate treatments and 7 and 14% in the urea treatments at rates of 100 and 300 kg N ha-1, respectively, compared to the control. N2O emission increased significantly with the increase in the nitrogen application rate. N2O emission was higher from ammonium sulphate treatments than from the urea treatments at the same application rate. A trade-off effect between CH4 and N2O emission was clearly observed. The N2O flux was very small when the rice paddy plots were flooded, but peaked at the beginning of the disappearance of floodwater. In contrast, the CH4 flux peaked during flooding and was significantly depressed by mid-season aeration (MSA). The results suggest that it is important to evaluate the integrative effects of water management and fertiliser application for mitigating greenhouse gas emissions in order to attenuate the greenhouse effect contributed by rice paddy fields.

578 citations


Journal ArticleDOI
TL;DR: An electrochemical investigation was carried out to study the corrosion of pure magnesium in 1 N NaCl at different pH values involving electrochemical polarisation, scanning tunnel microscopy (STM), measurement of hydrogen gas evolution and measurement of the elements dissolved from the magnesium specimen which were determined by inductively coupled plasma atomic emission spectrophotometry (ICPAES) as discussed by the authors.

530 citations


Journal ArticleDOI
TL;DR: Ch Chromosomal regions associated with marker segregation distortion in rice were compared based on six molecular linkage maps, suggesting that loci in these regions may be associated with preferential regeneration of japonica genotypes during anther culture.
Abstract: Chromosomal regions associated with marker segregation distortion in rice were compared based on six molecular linkage maps Mapping populations were derived from one interspecific backcross and five inter-subspecific (indica/japonica) crosses, including two F2 populations, two doubled haploid (DH) populations, and one recombinant inbred (RI) population Mapping data for each population consisted of 129-629 markers Segregation distortion was determined based on chi-square analysis (P < 001) and was observed at 68-318%, of the mapped marker loci Marker loci associated with skewed allele frequencies were distributed on all 12 chromosomes Distortion in eight chromosomal regions bracketed previously identified gametophyte (ga) or sterility genes (S) Distortion in three other chromosomal regions was found only in DH populations, where japonica alleles were over-represented, suggesting that loci in these regions may be associated with preferential regeneration of japonica genotypes during anther culture Three additional clusters of skewed markers were observed in more than one population in regions where no gametophytic or sterility loci have previously been reported A total of 17 segregation distortion loci may be postulated based on this study and their locations in the rice genome were estimated

450 citations


Journal ArticleDOI
TL;DR: It is clearly shown that increases in trace metal concentrations in the soils were generally extensive and obvious in urban and orchard soils, less so in vegetable soils, whilst rural and forest soils were subjected to the least impact of anthropogenic sources of trace metals.

358 citations


Journal ArticleDOI
01 Apr 1997-Geology
TL;DR: The left-lateral movement of the Ailao Shan-Red River shear zone lends support to the hypothesis of continental extrusion resulting from the collision of India with Asia as mentioned in this paper.
Abstract: Left-lateral movement of the Ailao Shan–Red River shear zone lends support to the hypothesis of continental extrusion resulting from the collision of India with Asia. Our new observations from northwestern Yunnan, China, and northwestern Vietnam on different sides of the shear zone demonstrate that the sinistral offset was ∼600 km according to correlations of Permian-Triassic flood basalt successions and late Paleogene highly potassic mafic magmas. We conclude that the shear was propagating on the South China continental margin and does not correspond to a suture between South China and Indochina. Furthermore, the highly potassic magmas were emplaced from ca. 40 to 30 Ma, before the shear movement, which was caused by the late Oligocene to early Miocene (ca. 27–22 Ma) extrusion activity. This suggests that a late Eocene to early Oligocene intraplate extension, possibly induced by delamination of thickened continental lithosphere, took place in northwestern Yunnan (or eastern Tibet) as a response to the India-Asia collision. This extension, and sea-floor spreading of the South China Sea that began ca. 30 Ma, could have accounted for the initiation of the Ailao Shan–Red River shear zone.

337 citations


Journal ArticleDOI
TL;DR: In this article, the microstructural changes of nano-SnO2 have been systematically studied using x-ray diffraction and Raman spectroscopy, and two major Raman peaks N-1 and N-2 in accordance with Matossi's force constant model have been found.
Abstract: The microstructural changes of nano-SnO2 have been systematically studied using x-ray diffraction and Raman spectroscopy. The nano-SnO2 grain assemblage possesses some features of the rutile structure, but has a large amount of defects: vacancies of oxygen, vacancy clusters, and local lattice disorder at the interface and interior surface, which lead to a significant lattice distortion and an evident space-symmetry reduction of D-4h(14) and the appearance of a group of new Raman peaks. Two major Raman peaks N-1 and N-2 in accordance with Matossi's force constant model have been found. When the annealing temperature is close to 673 K, the density of vacant lattice sires and local lattice disorders decreased rapidly in the grains, and the lattice distortion and Raman peaks N-1 and N-2 almost disappeared at the same time. It suggests that N-1 and N-2 are closely related to the microstructural change of the nanocluster grains, or in other words, N-1 and N-2 peaks mark an additional characteristic of space symmetry of the grain assemblage of nano-SnO2. The Raman peak N-3 may be related to local SnO2 clusters and vacancy clusters.

255 citations


Journal ArticleDOI
TL;DR: In this article, the authors recognized the consistent occurrence of the subduction wedge and collision prism onshore and offshore Taiwan and reconstructed the evolution of the accretionary prism during subduction and collision tectonics of Taiwan.

253 citations


Journal ArticleDOI
30 Dec 1997-Wear
TL;DR: A 2-ethyl hexoic acid (EHA) surface modified TiO2 nanoparticle with an average diameter of 5 nm was chemically synthesized in this article, and the frictionreduction and anti-wear behaviors of the prepared EHA-TiO2 as an oil additive in liquid paraffin were evaluated with a four-ball wear tester.

244 citations


Journal ArticleDOI
TL;DR: In the presence of a catalytic amount of triphenylphosphine, methyl 2,3-butadienoate smoothly reacted with aromatic or heteroaromatic N -tosylimines at room temperature to afford the [3+2] cycloaddition product in excellent yield as mentioned in this paper.

Journal ArticleDOI
TL;DR: A hypothetical model of coexistence of “Reactive oxygen cycle” with Q cycle and H+ cycle in mitochondrial respiratory chain to combine both processes of univalent electron leak for production of superoxide and of proton leak across inner mitochondrial membrane is proposed.
Abstract: Recently, we proposed a hypothetical model of coexistence of “Reactive oxygen cycle” with Q cycle and H+ cycle in mitochondrial respiratory chain to combine both processes of univalent electron leak for production of superoxide and of proton leak across inner mitochondrial membrane. This review presents a more detailed description of this model and summarizes the supporting experimental evidence obtained.

Journal ArticleDOI
13 Nov 1997-Nature
TL;DR: This analysis suggests that this new taxon represents a part of the early therian radiation before the divergence of living marsupials and placentals; that therians and multituberculates are more closely related to each other than either group is to other mammalian lineages.
Abstract: A new symmetrodont mammal has been discovered in the Mesozoic era (Late Jurassic or Early Cretaceous period) of Liaoning Province, China. Archaic therian mammals, including symmetrodonts, are extinct relatives of the living marsupial and placental therians. However, these archaic therians have been mostly documented by fragmentary fossils. This new fossil taxon, represented by a nearly complete postcranial skeleton and a partial skull with dentition, is the best-preserved symmetrodont mammal yet discovered. It provides a new insight into the relationships of the major lineages of mammals and the evolution of the mammalian skeleton. Our analysis suggests that this new taxon represents a part of the early therian radiation before the divergence of living marsupials and placentals; that therians and multituberculates are more closely related to each other than either group is to other mammalian lineages; that archaic therians lacked the more parasagittal posture of the forelimb of most living therian mammals; and that archaic therians, such as symmetrodonts, retained the primitive feature of a finger-like promontorium (possibly with a straight cochlea) of the non-therian mammals. The fully coiled cochlea evolved later in more derived therian mammals, and is therefore convergent to the partially coiled cochlea of monotremes.

Journal ArticleDOI
TL;DR: In this paper, the IAP (Institute of Atnjospheric Physics) land-surface model (IAP94) is described and validated with field measurements in off-line simulations.
Abstract: The IAP (Institute of Atnjospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attentionhas been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log-linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model’s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.

Journal ArticleDOI
TL;DR: The evidence indicates that UgV is probably of relatively recent origin, that such variants do not appear often, and that the current epidemic has resulted from the rapid spread of UgV to infect plants and to invade regions in which ACMV already occurred.
Abstract: Summary To study the cause of the current epidemic of severe mosaic in Ugandan cassava, PCR analysis was used to detect and identify African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and the recently reported recombinant geminivirus (UgV), which is derived from ACMV and EACMV, in leaf extracts from cassava plants grown from cuttings in the glasshouse at Dundee. The cuttings were collected from plants showing symptoms of different severities and growing at different sites in Uganda inside, at the periphery of, and outside, the area affected by the epidemic. ACMV occurred throughout the nine districts sampled but UgV was detected only in the area affected by the epidemic. EACMV was not found in Uganda. Most plants containing ACMV alone expressed mild or moderate mosaic, whereas very severe mosaic developed in most plants containing UgV plus ACMV and a few of those containing UgV only. Very severe mosaic in cassava from southern Sudan was likewise associated with co-infection by UgV and ACMV. The very severe disease was reproduced by graft-inoculating geminivirus-free cassava with UgV plus ACMV; plants inoculated with either UgV or ACMV developed severe or moderate symptoms, respectively. Unlike ACMV, Malawian EACMV did not enhance the severity of symptoms induced by UgV. However, a very severely affected plant from Ukerewe Island, Tanzania, contained ACMV and EACMV but not UgV. UgV attained a much greater concentration in cassava than did ACMV but the opposite occurred in Nicotiana benthamiana. In neither host was total virus antigen concentration affected by co-infection. Factors affecting the genesis, selection and spread of UgV are discussed. The evidence indicates that UgV is probably of relatively recent origin, that such variants do not appear often, and that the current epidemic has resulted from the rapid spread of UgV to infect plants and to invade regions in which ACMV already occurred. The novel type of virus complex so produced, consisting of an interspecific recombinant virus (UgV) and one of its parents (ACMV), typically has even more severe effects than UgV alone.

Journal ArticleDOI
TL;DR: In this article, the wear traces and the transfer film were observed by scanning electron microscopy (SEM) and it was inferred that the transferred film contributed largely to the decreased friction coefficient and wear rate of the filled PEEK composites.

Journal ArticleDOI
TL;DR: In this article, geochemical and Sm-Nd isotopic data are presented for basaltic volcanic rocks from the Longsheng Ophiolite, which were crystallized at 977 ± 10 Ma and tectonically emplaced into the Danzhou Group (Banxi equivalent) along the southern margin of the Yangtze Block, SE China during the Neoproterozoic.
Abstract: Geochemical and Sm-Nd isotopic data are presented for basaltic volcanic rocks from the Longsheng Ophiolite, which were crystallized at 977 ± 10 Ma and tectonically emplaced into the Danzhou Group (Banxi equivalent) along the southern margin of the Yangtze Block, SE China during the Neoproterozoic. The volcanic rocks have undergone low-grade alteration and metamorphism, displaying high Na2O contents (>5%) and a large variation of mobile elements, but a relatively small range of immobile elements. With enrichment of Th and LREEs, relatively low high-field-strength elements and other REEs, and the Ta-Nb-Ti negative anomaly, the volcanic rocks are geochemically similar to basalts forming in subduction-related environments, typical of the “supra-subduction zone” ophiolites. Nd isotopes of the volcanic rocks preclude a MORB-like depleted mantle source for the Longsheng Ophiolite, though their Sm-Nd isotopic systems have been rehomogenized during the late Neoproterozoic alteration. The Longsheng volcanic rocks, therefore, are interpreted to have been generated either by extension and thinning of a continental arc, or at a backarc side of continental arc during the early stage of the backarc spreading.

Journal ArticleDOI
TL;DR: In this article, the authors reconstructed the climatic and environmental variations since the Last Interglaciation based on the study of the upper 268 m of the 309m-long Guliya ice core.
Abstract: The climatic and environmental variations since the Last Interglaciation are reconstructed based on the study of the upper 268 m of the 309-m-long Guliya ice core. Five stages can be distinguished since the Last Interglaciation from the δ 18O record in the Guliya ice core: Stage 1 (Deglaciation), Stage 2 (the Last Glacial Maximum), Stage 3 (interstadial), Stage 4 (interstadial in the early glacial maximum) and Stage 5 (the Last Interglaciation). Stage 5 can be divided further into 5 substages; a, b, c, d, e. The δ 18O record in the Guliya ice core indicates clearly the close correlation between the temperature variation on the Tibetan Plateau and the solar activities. The study indicates that the solar activity is a main forcing to the climatic variation on the Tibetan Plateau. Through a comparison of the ice core record in Guliya with that in the Greenland and the Antarctic, it can be found that the variation of large temperature variation events in different parts of the world is generally the same, but the variation amplitude of temperature is different.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the disproportionation of aqueous Au(I) chloride complexes at elevated temperature using the solubility method and obtained the following polynomial: log KA1 = −13.55 + 8593/T−700610/T2 (T =Kelvin, valid from 25 to 200°C).

Journal ArticleDOI
TL;DR: In this article, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes.
Abstract: From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes. From the time delays, one can estimate the size of the region dominating the production of the UV emission lines in this source. We find the strong UV emission lines to respond to continuum variations with time delays of about 23-31 for Lyα, 27 for C IV λ1549, 19-24 for N V λ1240, 17-18 for Si IV λ1400, and 07-10 for He II λ1640. The most remarkable result, however, is the detection of apparent time delays between the different UV continuum bands. With respect to the UV continuum flux at 1315 A, the flux at 1485 A, 1740 A, and 1825 A lags with time delays of 021, 035, and 028, respectively. Determination of the significance of this detection is somewhat problematic since it depends on accurate estimation of the uncertainties in the lag measurements, which are difficult to assess. We attempt to estimate the uncertainties in the time delays through Monte Carlo simulations, and these yield estimates of ~007 for the 1 σ uncertainties in the interband continuum time delays. Possible explanations for the delays include the existence of a continuum-flux reprocessing region close to the central source and/or a contamination of the continuum flux with a very broad time-delayed emission feature such as the Balmer continuum or merged Fe II multiplets.

Journal ArticleDOI
TL;DR: In this paper, radio galaxies can heat and support the cluster gas with injected cosmic-ray protons and magnetic field densities, which are permitted by Faraday rotation and gamma-ray observations of clusters of galaxies.
Abstract: The masses of clusters of galaxies estimated by gravitational lensing exceed in many cases the mass estimates based on hydrostatic equilibrium. This may suggest the existence of nonthermal pressure. We ask if radio galaxies can heat and support the cluster gas with injected cosmic-ray protons and magnetic field densities, which are permitted by Faraday rotation and gamma-ray observations of clusters of galaxies. We conclude that they are powerful enough to do this within a cluster radius of roughly 1 Mpc. If present, nonthermal pressures could lead to a revised estimate of the ratio of baryonic mass to total mass, and the apparent baryonic overdensity in clusters would disappear. In consequence, Ωcold, the clumping part of the cosmological density Ω0, would be larger than 0.4 h -->−1/250.

Journal ArticleDOI
01 Jul 1997-Polymer
TL;DR: In this article, the effect of adding nonaphenol polyethyleneoxy (10) ether (OP 10 ) into the electropolymerization solution of pyrrole on the tensile strength and structure of the as-prepared polypyrrole (PPy) films was reported.

Journal ArticleDOI
TL;DR: In this paper, the electronic structure of crystalline Y2O3 was investigated by first-principles calculations within the local density approximation (LDA) of the density-functional theory.
Abstract: The electronic structure of crystalline Y2O3 is investigated by first-principles calculations within the local-density approximation (LDA) of the density-functional theory. Results are presented for the band structure, the total density of states (DOS), the atom-and orbital-resolved partial DOS. effective charges, bond order, and charge-density distributions. Partial covalent character in the Y-O bonding is shown, and the nonequivalency of the two Y sites is demonstrated. The calculated electronic structure is compared with a variety of available experimental data. The total energy of the crystal is calculated as a function of crystal volume. A bulk modulus B of 183 Gpa and a pressure coefficient B' of 4.01 are obtained, which are in good agreement with compression data. An LDA band gap of 4.54 eV at Gamma is obtained which increases with pressure at a rate of dE(g)/dP = 0.012 eV/Gpa at the equilibrium volume. Also investigated are the optical properties of Y2O3 up to a photon energy of 20 eV. The calculated complex dielectric function and electron-energy-loss function are in good agreement with experimental data. A static dielectric constant of epsilon(O)= 3.20 is obtained. It is also found that the bottom of the conduction band consists of a single band, and direct optical transition at Gamma between the top of the valence band and the bottom of the conduction band may be symmetry forbidden.

Journal ArticleDOI
TL;DR: In this article, tree species diversity of four tropical forest vegetation types was investigated in Xishuangbanna, southwestern China and the results reveal the long-tailed rank/abundance diagrams of these forests.
Abstract: Tree species diversity of four tropical forest vegetation types was investigated in Xishuangbanna, southwestern China These are: tropical seasonal rain forest, tropical montane rain forest, evergreen broad-leaved forest and monsoon forest over limestone A total of 17 samples were taken and four species diversity indices were calculated: Shannon-Wiener's H′, the complement of Simpson's index, d′, Fisher's α and evenness index E The results reveal the long-tailed rank/abundance diagrams of these forests However, this feature is greatly reduced in the samples of monsoon forest over limestone Tropical seasonal rain forest shows the highest tree species diversity of all four vegetation types Owing to the variation of microenvironment, diversity values within the same vegetation type vary between the samples from different patches The tree species diversity of single-dominant rain forest is not significantly lower than that of mixed rain forest, because the dominant species of some single-dominant rain forests are principally in the emergent layer This is composed of sparse and huge trees of one species and, consequently, creates a unique canopy architecture and more heterogeneous microenvironments for the more diversified species composition under the emergent layer The occurrence of tree species with small population sizes, particularly of species represented by only one individual, is highly correlated with the tree species diversity of the local forest vegetation They are crucial elements in the richness of local biodiversity

Journal ArticleDOI
TL;DR: To promote land application of sewageSludge in China, a statewide survey of sewage sludge production and harmful components in sewage slud should be carried out.

Journal ArticleDOI
01 Aug 1997-Wear
TL;DR: In this paper, the tribological behavior of polyetheretherketone (PEEK) filled with nanometer SiC was investigated on a block-on-ring machine by running a plain carbon steel ring against the PEEK composite block.

Journal ArticleDOI
30 Dec 1997-Wear
TL;DR: In this article, the influence of nanometer SiC, micron SiC and whisker SiC fillers on the friction and wear of polyetheretherketone (PEEK) composites was studied.

Journal ArticleDOI
TL;DR: In this paper, the authors used satellite imagery to quantify rates and patterns of landscape change between 1972 and 1988 in the Changbai Mountain Reserve and its adjacent areas in the People's Republic of China and North Korea.
Abstract: Satellite imagery was used to quantify rates and patterns of landscape change between 1972 and 1988 in the Changbai Mountain Reserve and its adjacent areas in the People’s Republic of China and North Korea. The 190,000 ha Reserve was established as an International Biosphere Reserve by The United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1979. It is the most important natural landscape remaining in China’s temperate/boreal climate. The images used in this research cover a total area of 967,847 ha, about three-fourths of which is in China. Imagery from 1972 and 1988 was classified into 2 broad cover types (forest and non-forest). Overall, forests covered 84.4% of the study area in 1972 and 74.5% in 1988. Changes in forest cover within the Reserve were minimal. The loss of forest cover outside the Reserve appears to be strongly associated with timber harvesting at lower elevations. Landscape patterns in 1988 were more complex, more irregular, and more fragmented than in 1972. This is one of the few studies to assess landscape changes across two countries. The rates and patterns of forest-cover loss were different in China and North Korea. In North Korea, extensive cutting appears to have occurred prior to 1972 and this has continued through 1988 while in China, most cutting appears to have occurred since 1972.

Journal ArticleDOI
TL;DR: In this article, a transfer-matrix treatment of the tunnel conductance and magnetoresistance for tunneling through ferromagnet/insulator (semiconductor) single junctions and double junctions subject to a dc bias is presented.
Abstract: Based on the two-band model, we present a transfer-matrix treatment of the tunnel conductance and magnetoresistance for tunneling through ferromagnet/insulator (semiconductor) single junctions and double junctions subject to a dc bias. Our results are qualitatively in agreement with the experimental measurements for the single junction. For the double junction, we find that there exists, spin-polarized resonant tunneling and giant tunnel magnetoresistance. The highest value of the magnetoresistance in a double junction can reach 90%. We anticipate that our results will stimulate some interest in experimental efforts in designing spin-polarized resonant-tunneling devices.

Journal ArticleDOI
15 May 1997-Cancer
TL;DR: The apoptosis‐related genes p53, bcl‐2, and c‐myc have important roles in the regulation of programmed cell death, and thus may be involved in the process of the suspected PROG‐induced apoptosis.
Abstract: BACKGROUND Progesterone (PROG) has been shown to reduce the risk of developing ovarian carcinoma in postmenopausal women who have undergone estrogen and progestogen replacement therapy, and it has been clinically used to treat some types of ovarian tumors. It is not yet clear whether or not the antitumor activity of progestogen is due to its ability to induce apoptosis in precarcinomatous and carcinomatous ovarian cells. The apoptosis-related genes p53, bcl-2, and c-myc have important roles in the regulation of programmed cell death, and thus may be involved in the process of the suspected PROG-induced apoptosis. METHODS Antiproliferation effects of PROG on 3AO and AO ovarian carcinoma cells were determined by 3H-thymidine incorporation. Apoptosis of the PROG-treated cells was determined by DNA laddering analysis and was quantitated by both nuclear condensation and flow cytometry after cells were stained with propidium iodide. Cell cycle analysis was also performed by flow cytometry. The expression of p53, bcl-2, and c-myc after 72 hours of PROG treatment was detected by Northern blot analysis. RESULTS In both 3AO and AO cell lines, cells proliferation was maximally inhibited by PROG after 72 hours of treatment at 10 μM concentration. Under the same conditions, more than 50% of PROG-treated cells had undergone apoptosis, whereas less than 3% of the cells were apoptotic in untreated cell cultures. After exposure to PROG for 72 hours, cells were arrested in the G1 phase of the cell cycle, and the levels of p53 mRNA were remarkably increased in both cell lines. No changes in expression of bcl-2 or c-myc were detected. CONCLUSIONS PROG significantly inhibited cell proliferation and induced apoptosis in both of the ovarian carcinoma cell lines tested in this study. PROG treatment markedly up-regulated p53 expression in these cells, indicating involvement of p53 in PROG-induced apoptosis. Cancer 1997; 79:1944-50. © 1997 American Cancer Society.