Pattern analysis of stem cell differentiation during <Emphasis Type="Italic">in vitro Arabidopsis</Emphasis> organogenesis

Plant somatic cells have the capability to switch their cell fates from differentiated to undifferentiated status under proper culture conditions, which is designated as totipotency. As a result, plant cells can easily regenerate new tissues or organs from a wide variety of explants. However, the mechanism by which plant cells have such remarkable regeneration ability is still largely unknown. In this study, we used a set of meristem-specific marker genes to analyze the patterns of stem cell differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro. Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis.     

Enhancement of cell growth by intracellularly expressed herpes simplex virus thymidine kinase

A recombinant cell line (NIH3T3:pLtkSN) was made by infecting parental cells (NIH3T3) with a recombinant retrovirus (pLtkSN) encoding herpes simplex virus thymidine kinase (HSVtk) gene. The cells expressing HSVtk (NIH3T3:pLtkSN) grew 2.3 times more than the parental cells (NIH3T3) in Dulbecco's Modified Eagles Media containing 10% (v/v) horse serum. The NIH3T3:pLtkSN cells also showed a significant enhancement in the maximal cell concentration and the specific growth rate even at 2.5% serum concentration. The specific O2 uptake rate of NIH3T3 was 2.1 times greater than that of NIH3T3:pLtkSN. Under both O2-limited and O2-unlimited conditions, it appears that HSVtk plays an important role in enhancing the growth characteristics of animal cells.     

Evidence for the signaling role of methyl jasmonate, methyl salicylate and benzothiazole between poplar (Populus simonii × P. pyramidalis ‘Opera 8277’) cuttings

Interplant communication has been widely demonstrated in plants, especially in herbaceous plants. In this study, mechanical damage was shown to affect the levels of pyrochatechol, chlorogenic acid, gallic acid and p-hydroxyl benzoic acid in poplar (Populus simonii × P. pyramidalis ‘Opera 8277’) cuttings, indicating the activation of defense response. In neighboring intact cuttings, the levels of those phenolics also varied when compared to the control, suggesting the interplant communication between poplar cuttings. Three volatiles, methyl jasmonate, methyl salicylate and benzothiazole, were detected in volatiles emitted from mechanically damaged poplar cuttings. All of them can induce changes in the levels of four phenolics. Therefore, they could act as airborne signals between P. simonii × P. pyramidalis ‘Opera 8277’ cuttings. The different change patterns of phenolic contents induced by different volatiles imply that the defense response activated in neighboring plants may be regulated by multiple signaling pathways. The results also suggest that the entire defense response of plants involves a variety of airborne signals in wound-induced volatiles.     

A rapid extraction method for detecting aflatoxin producing isolates

A rapid extraction method for screening aflatoxin producing potential ofAspergillus flavus group isolates is described. The method is performed using a moist wheat medium with ca. five infected grains extracted with 2 mL of chloroform, and using thin layer chromatography. This method was proved with 95A. flavus isolates from animal feeds.     

Association of viral and plasmid DNA with the nuclear matrix during productive infection

The association of simian virus 40 (SV40) DNA or plasmid DNA in subcellular fractions from either infected or transfected cells was examined. In lytically infected cells, approx. 25% of viral specific DNA during the infection cycle was retained in nuclei after washing with low ionic strength buffer and 1% Triton X-100. Viral replicating DNA found in the nuclear matrix was capable of performing limited DNA synthesis by the endogenous DNA polymerase in vitro. Viral DNA synthesized in vitro hybridized preferentially to SV40 Hind-III B and C fragments which are in proximity to the origin of replication. In plasmid-transfected COS-7 cells (SV40-transformed cells), the amount of plasmid DNA found in the nuclear matrix was related to its replication efficiency in cells. More than 80% of the plasmid DNA was tightly associated with subnuclear structures. Little or no plasmid DNA was found in the cytoplasmic fraction. The results suggest that, in extrachromosomal model systems, the association of DNA with nuclear matrix is important for the regulation of DNA replication.     

Sliding controller design for a nonlinear fermentation system

The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.     

The formation and characteristics of China's existing system

Conclusion To sum up, the character of China's existing system is basically all-embracing totalitarianism formed by the combination of the old tradition of feudal-despotism and the new tradition of Stalinism. This system is the basic source of all the social evils in China.The ultimate aim of the democratic movement is to transform the old, allembracing totalitarian system and to establish a democratic, free, humane, and rational new system. The present ruling group is the beneficiary and defender of the existing system. The contradictions and conflicts between reformers who want to transform the old system and the hardliners who want to protect the old system formed the crux of the struggle of the 1989 democratic movement. Because the democratic movement lacked preparation in theory, organization, tactics and strategy, and because the ruling group controls the means of dictatorship — especially the army —military force was used to suppress the democratic movement with brutal bloodshed. In order to promote the democratic movement, we should sum up some lessons and experiences. First, we should study in depth the existing system and oppose feudaldespotism and Stalinism through effective propaganda and education. Second, we should arouse the democratic consciousness of the broad masses of the people, uniting with them and the healthy elements inside the Party, government, and army to struggle for the smashing of the old system and the establishment of a new system.Su Shaozhi is former Director of the Institute for the Study of Marxism-Leninism and Mao Zedong Thought, Chinese Academy of Social Sciences, Beijing, and currently Visiting Professor at the Bradley Institute for Democracy and Public Values, Marquette University, Milwaukee, Wisconsin