Replication phenomenon

Fig. 3 Replication phenomenon during polymerization. (View this art in color at www. dekker.com.)...

The drug is found to inhibit the replication phenomenon of the influenza type A viruses specifically at low concentrations. The above admantanamine essentially possesses two vital mechanisms, namely ... 

Viruses, in general, utilize only the enzyme-system of the host-cell for two purposes, namely first, to synthesize DNA and secondly, to replicate virus, thereby enabling it to perform their usual metabolic activities. They may carry out either the transformation or the replication processes of the cell at the same time. By virtue of the fact that viruses are obligate intracellular parasites, therefore, their replication phenomenon solely depends on the host s cellular processes. 

The drug gets converted by the help of cellular enzymes into corresponding mono-, di-, and triphosphate structural analogues which strategically interfere with viral nucleic acid replication phenomenon, particularly jeopordizing the very preliminary steps involved in DNA-synthesis. It has been observed that the antiviral effect is, in certain instances, proved to be much superior to that of idoxuridine and cytarabine. 

Traditional commercial catalyst supports are designed to allow fragmentation to take place in this ordered fashion. If the fragmentation step takes place under ideal conditions, one particle of supported catalyst will yield one polymer particle with roughly the same shape. This is referred to as replication phenomenon and is one of the most remarkable characteristics of heterogeneous olefin polymerization. 

The last alternative is the only one that has industrial interest much catalyst research is behind the design of catalyst particles that can be properly fragmented to form uniform polymer partides. This leads to the so-called replication phenomenon , whereby the size distribution of the catalyst partides is neatly replicated by the size distribution of the polymer particles exiting the reactor, as illustrated in... 

Figure 8.32. Proper replication of the catalyst particles is essential for stable reactor operation and also for the handling of the polymer particles in post-reactor processes. Reactor residence time distribution in CSTRs may have an important effect on the replication phenomenon the references at the end of the chapter provide more details on this subject [46-50].

Fig. 8.32. Replication phenomenon for polymerization with heterogeneous coordination catalysts.

The basic influence of the catalyst characteristics on the polymer morphology through the replication phenomenon are well known ). The SB 12 catalyst is in the shape of spherical particles having a very narrow particle size distribution (fig. 1). The width of the particle size distribution can be estimated by the polydispersity index (PI) equal to the weight (Dw) to number (Dn) mean diameter ratio ... 

ITowever, most normal somatic cells lack telomerase. Consequently, upon every cycle of cell division when the cell replicates its DNA, about 50-nucleotide portions are lost from the end of each telomere. Thus, over time, the telomeres of somatic cells in animals become shorter and shorter, eventually leading to chromosome instability and cell death. This phenomenon has led some scientists to espouse a telomere theory of aging that implicates telomere shortening as the principal factor in cell, tissue, and even organism aging. Interestingly, cancer cells appear immortal because they continue to reproduce indefinitely. A survey of 20 different tumor types by Geron Corporation of Menlo Park, California, revealed that all contained telomerase activity. 

Fig. 5 illustrates a peculiar kinetic phenomenon which occurs when an initially disordered alloy is first annealed at temperature T corresponding to area b in Fig. 1 and then quenched to the final temperature T into the spinodal instability area d antiphase boundaries "replicate , generating approximately periodic patterns. This phenomenon reflects the presence of critical, fastest growing concentration waves under the spinodal instability (the Calm waves ). Lowering of the temperature to T < T results in lowering of the minority concentration minimum ("c-well ) within APB, while the expelled solute atoms build the c-bank adjacent to the well . Due to the... 

There is a specific dilution rate known as critical dilution rate where a washout phenomenon takes place. At the critical dilution rate there is not enough time for the microorganisms to replicate. 

Autocatalysis, although not rare, is not common either. A study of this phenomenon is crucial for the treatment of oscillating reactions, which are presented in Section 8.8. If the data give an indication of autocatalytic behavior, one quick laboratory test is to use the leftover solution from a completed reaction as the solvent for the next. If the replicate is faster than the first trial, autocatalysis is suggested. 

Although it is difficult to obtain dmgs capable of intermpting viral replication, it had been known for many years that infection of a host with one vims could sometimes prevent infections with a second, quite unrelated vims. This phenomenon was called... 

Abstract. In eukaryotic cells, replicated DNA molecules remain physically connected from their synthesis in S phase until they are separated during anaphase. This phenomenon, called sister chromatid cohesion, is essential for the temporal separation of DNA replication and mitosis and for the equal separation of the duplicated genome. Recent work has identified a number of chromosomal proteins required for cohesion. In this review we discuss how these proteins may connect sister chromatids and how they are removed from chromosomes to allow sister chromatid separation at the onset of anaphase. 

Virus restriction and modification by the host We have already seen that one form of host resistance to virus arises when there is no receptor site on the cell surface to which the virus can attach. Another and more specific kind of host resistance involves destruction of the viral nucleic acid after it has been injected. This destruction is brought about by host enzymes that cleave the viral DNA at one or several places, thus preventing its replication. This phenomenon is called restriction, and is part of a general host mechanism to prevent the invasion of foreign nucleic acid. 

If the virus has double-stranded RNA (ds RNA), this RNA serves as a template in a manner analogous to DNA. There are three classes of viruses with ss RNA and they differ in the mechanism by which mRNA is synthesized. In the simplest case, the incoming viral RNA is the plus sense and hence serves directly as mRNA, and copies of this viral RNA are also copied to make further mRNA molecules. In another class, the viral RNA has a minus (-) sense. In such viruses a copy is made (plus sense) and this copy becomes the mRNA. In the case of the retroviruses (causal agents of certain kinds of cancers and AIDS), a new phenomenon called reverse transcription is seen, in which virion ss RNA is copied to a double-stranded DNA (through a ss DNA intermediate) and the ds DNA then serves as the template for mRNA synthesis (thus ss RNA ss DNA ds DNA). Retrovirus replication is of unusual interest and complexity. 

In addition, the authors suggest that all such systems must have a semi-permeable active boundary (membrane), an energy transduction apparatus and (at least) two types of functionally interdependent macromolecular components (catalysts and records). Thus, the phenomenon of life requires not only individual self-replication and self-sustaining systems, but it also requires of such individual systems the ability to develop a characteristic, evolutionary dynamic and a historical collectivist organisation. 

How can negative fluctuations in entropy production occur or be triggered As Manfred Eigen shows in his evolution theory, fluctuations in entropy production can be caused by the coming into being of a self-replicating molecular species which is capable of selection. Autocatalytically active mutants can also have the same effect. Looked at this way, the phenomenon of evolution consists of a continuous series of instabilities, i.e., collapses of stationary states. 

Therefore, there is no doubt that inhibition of PARP leads to DNA hypermethylation in vivo. But what is the molecular mechanism behind this phenomenon To get an insight into this mechanism, PARPs were inhibited at different phases of the cell cycle [41]. Both the mRNA and protein levels of Dnmtl were precociously increased in Gl/S phase. These elevated Dnmtl levels, affecting the normal equilibrium between p21 and Dnmtl in this phase, led to higher than normal levels of the PCNA-Dnmtl complex, and thus, to higher DNA methylation of the sequences replicated in early S phase (CpG islands are early replicating) (see Fig. 3d). 

The approach applies to repeated observations pertinent to each treatment, or to observations in two-dimensional arrays, if one factor (which could serve as the block in a two-factor analysis) is considered as a replicate entity. The idea is illustrated in the case of permeation fluxes through a membrane [15] with pertinent calculations given in Table 3. If the effect of the k = 6 salts is considered as a replicate (random) phenomenon, and the observed and calculated values (N= 2) are ranked according to the flux observations, the probability computed by an appropriate modification of Eq.(3) as... 

Loros Of course, Synecococcus doesn t have a nucleus but it displays perfectly functional rhythms. There may be something there. Who has replicated the Acetahularia work Another perfectly reasonable explanation of the. Acetabularia phenomenon is that parts of the clock requiring daily transcription are encoded for in the chloroplast. It could be a plastid clock. 

---