Cellular Location and Some Properties of Proteolytic Enzymes of Rumen Bacteria

Several physical and chemical techniques were used to extract, and to identify the location of, proteolytic enzymes associated with mixed rumen bacteria. Most activity was removable by gentle physical methods such as shaking and brief blending, without cell disruption, indicating that it was associated with coat and capsular material. Proteases were present also in the cell envelope, corresponding to the inner membrane fraction of gram-negative bacteria, and intracellularly and were removable by detergent and French press treatment. Temperature and pH profiles were obtained for the coat enzymes, likely to be the most important in the digestion of food protein. Inhibition studies indicated that these proteases, and those of the whole bacterial fraction from rumen fluid, were predominantly of the cysteine protease type.     

Cellular Electrophoretic Mobility and the Mitotic Cycle

The electrophoretic mobility of RPMI No. 41 cells grown in suspension, parasynchronized by double thymidine blocking and cold shock, is reported. No. 41 cells have a higher electrophoretic mobility during the mitotic peak phase than at other times in the mitotic cycle. Treatment of parasynchronous cells by neuraminidase reduces the mobility to the same value irrespective of the stage of the cells in the mitotic cycle. The higher electrophoretic mobility of cells in mitotic peak phase is probably due to a higher surface charge density at this time, possibly caused by a higher concentration of ionized neuraminic acid carboxyl groups at the hydrodynamic shear layer. The mobility of nonsynchronous rapidly and slowly growing cells differs; neuraminidase reduces their mobility by proportionately similar amounts. The results suggest that the differences in mobility between rapidly and slowly growing cells cannot be accounted for exclusively by differences in the amount of neuraminic acid groups at the shear layer.     

Simulating the Conversion of Rural Settlements to Town Land Based on Multi-Agent Systems and Cellular Automata

Rapid urbanization in China has triggered the conversion of land from rural to urban use, particularly the conversion of rural settlements to town land. This conversion is the result of the joint effects of the geographic environment and agents involving the government, investors, and farmers. To understand the dynamic interaction dominated by agents and to predict the future landscape of town expansion, a small town land-planning model is proposed based on the integration of multi-agent systems (MAS) and cellular automata (CA). The MAS-CA model links the decision-making behaviors of agents with the neighbor effect of CA. The interaction rules are projected by analyzing the preference conflicts among agents. To better illustrate the effects of the geographic environment, neighborhood, and agent behavior, a comparative analysis between the CA and MAS-CA models in three different towns is presented, revealing interesting patterns in terms of quantity, spatial characteristics, and the coordinating process. The simulation of rural settlements conversion to town land through modeling agent decision and human-environment interaction is very useful for understanding the mechanisms of rural-urban land-use change in developing countries. This process can assist town planners in formulating appropriate development plans.     

Question 7: The Vesicle World: The Emergence of Cellular Life can be Related to Properties Specific to Vesicles

The question “What was the minimum number of genes necessary in the early cell” is rephrased as “Is it feasible to assume that early cells had no genes?” It is shown that a kind of primitive life process could exist on the basis only of properties specific to vesicles, and that it would have the potential to evolve into more complex cell-like processes.     

Properties of Johnsongrass Chlorotic Stripe Mosaic Virus

Physicochemical, biological, and cytopathological properties of Johnsongrass chlorotic stripe mosaic virus (JCSMV) found in Iran were investigated. Virus particles were polyhedral, showed a knobbed surface structure, were c. 30 nm in diameter and had a buoyant density of 1. 359 g/ml in cesium chloride. Virions contained one major protein with a molecular weight of 41 kd and a single species of ssRNA with a molecular weight of 1. 43 × 10⁶ d. Acid hydrolysis of the virus followed by thin-layer electrophoresis gave the following molar percentages of the bases: A: 23. 5, G: 27. 5, C: 26 and U: 23. Separation of nucleotides of the viral RNA using alkaline hydrolysis was not successful. Mechanical inoculation of freshly purified virus or isolated RNA failed to infect Johnsongrass or maize plants. The virus was readily detected by ELISA in seeds from infected plants and young seedlings raised from such seeds, but not in later stages of growth. Ultrathin sections of infected cells showed high concentrations of virus particles in the cytoplasm and vacuoles. Virus-like particles also occurred in the stroma of chloroplasts and mitochondria. Cisternae of endoplasmic reticulum (ER) were often extremely inflated and filled by a fine fibrillar material. Small membrane-associated vesicles were frequently found in ER elements and occurred also in the permuclear space. Based on particle structure, properties of the nucleic acid, molecular weight of the coat protein and cytopathology, the virus resembles carmoviruses. However, lack of mechanical transmissibility is not known for any virus classified with this group. No serological reaction was detected with a total of 30 antisera to carmoviruses and other isometric viruses.     

Purification and Properties of the Geminivirus Euphorbia Mosaic Virus

Euphorbia mosaic virus was purified from infected plants of Nicotiana benthamiana. Highest concentrations of virus particles were found in infected plant tissue between 10–12 days after inoculation. The enzyme driselase assisted in purification of the virus particles from the infected tissue yielding about 600 μg/kg of plant material. Purified preparations showed a maximum absorption at 260–263 nm and the ratio of absorption at 260 and 280 nm was 1.4. The viral nucleic acid was digestedby DNase I and S₁ Nuclease but not RNase A. A single coat protein with a MW of 32,000 d and two DNA bands with a MW 0.96 × 10⁶ d (2870 nucleotides) and 0.90 × 10⁶ d (2700 nucleotides) were associated with the purified virus particles. Virus specific DNA was isolated from infected tissue between 7 and 15 days after inoculations.     

山东烟台小麦土传病毒病由小麦黄花叶病毒和土传小麦花叶病毒相关病毒复合侵染所致

在山东省烟台地区的小麦上发生一种由土壤中禾谷多粘菌Polymyxa graminis传播的病毒病,感病小麦植株表现矮化褪绿和花叶症状.我们于1997年4月从病区采集感病小麦植株,进行了病毒种类鉴定.直接电镜观察发现有二种病毒粒子,一种粒子呈棒状,占大多数,其长度约为300nm和150nm; 另一种粒子呈线状,数量较少,长度为500nm～700nm.免疫电镜结果表明,棒状病毒粒子仅与土传小麦花叶病毒(soil-borne wheat mosaic virus, SBWMV)抗血清反应,而不与小麦黄花叶病毒(wheat yellow mosaic virus,WYMV)抗血清和小麦梭条斑花叶病毒(wheat spindle streat mosaic virus,WSSMV)抗血清反应;反之,线状病毒仅与WYMV、WSSMV抗血清反应,而不与SBWMV抗血清反应.用WYMV和SBWMV两种抗血清同时进行修饰时,线状病毒粒子和棒状病毒粒子均发生反应.     

Life Cycle Perspectives to Achieve Business Benefits: From Concept to Technique

The purpose of this paper is to describe how one pollution prevention tool, life-cycle assessment, can be used to identify and manage environmental issues associated with product systems. Specifically, this paper will describe what life-cycle assessment is, determine the key players in its development and application, and present ideas on how life-cycle assessment can be used today. LCA provides a systematic means to broaden the perspective of a company's decisionmaking process to incorporate the consideration of energy and material use, transportation, post-customer use, and disposal, and the environmental releases associated with the product system. LCA provides a framework to achieve a better understanding of the trade-offs associated with specific change in a product, package, or process. This understanding lays the foundation for subsequent risk assessments and risk management efforts by decision-makers.     

Very Simple Models, the Self-Modifying Automata and Chain of Self-Modifying Automata, Can Explain Self-Referential Properties of Living Beings

Very often, living beings seem able to change their functioning when external conditions vary. In order to study this property, we have devised abstract machines whose internal organisation changes whenever the external conditions vary. The internal organisations of these machines (or programs), are as simple as possible, functions of discrete variables. We call such machines self-modifying automata.These machines stabilise after any transient steps when they go indefinitely through a loop called p-cycle or limit cycle of length p. More often than not, the p in the cycle is equal to one and the cycle reduces to a fixed point.In this case the external value (v) can be considered as the index of function f such as: f_v(v)^–v and the machine has the property of self-replication and to be self-referential. Many authors, in computer and natural science, consider that self-referential objects are a main concept in comprehension of perception, behaviour and associations.In the third part, we have studied chains of automata. Only one automaton changes its internal organisation at each step. Chains of automata have better performances than single self-modifying automata: Higher frequency of fixed point occurrence and a shorter transient length. The performances of the chains of automata improve when the value of their internal states increases whereas the performances of single automata decrease.     

Growth Cycle of Predacious Bdellovibrios in a Host-Free Extract System and Some Properties of the Host Extract

Host-free growth and reproduction of a host-dependent strain of Bdellovibrio bacteriovorus incubated with an extract from host cells were studied. The morphological changes occurring in the cells were correlated with deoxyribonucleic acid (DNA) synthesis as measured by labeled nucleotide or orthophosphate incorporation. The host-free developmental cycle of Bdellovibrio is similar to that of the two-membered system; the early loss of flagella, the elongation into filaments, and multiple fission into flagellated progeny are typical for both host-free and intraperiplasmic development of bdellovibrios. Filament length and time of division appear to depend on the concentration of the host extract. Host extract was found to be heat stable and DNase stable, and Pronase sensitive and RNase sensitive. Addition of ribonucleic acid to the extract medium at various times during the Bdellovibrio growth cycle demonstrated that host extract is required continuously during the cycle for growth. The observations reported give a unified picture of Bdellovibrio development and allow for the suggestion that wild-type bdellovibrios depend upon the presence of some host factor for induction of DNA synthesis, whereas depletion of host factor triggers division. The ecological implications of such host dependence are discussed.