Resting phase

The death rate coefficient is usually relatively small unless inhibitoiy substances accumulate, so Eq. (24-10) shows an exponential rise until S becomes depleted to reduce [L. This explains the usual growth curve (Fig. 24-21) with its lag phase, logarithmic phase, resting phase, and declining phase as the effect of takes over. 

One of the important characteristics of living beings is to alternate between active and rest phases, but the underlying mechanism/s and functions... 

These models picture the mixing process as consisting of motion phases and rest phases. In a model proposed by Einstein (E3) and discussed by Jacques and Vermeulen (Jl) and Cairns and Prausnitz (C5), it is assumed that the time represented by a motion phase is much less than that by a rest phase. For the packed bed, the motion phase might be taken as the period when the fluid element is passing through the restriction between particles, and the rest phase as the period when the fluid element is in the void space. If values are assigned to the probabilities of motion or rest, consideration of the geometry of the fluid elements motions will lead to... 

Giddings and Eyring (G2), Giddings (Gl), and Klinkenberg (KIO) have also proposed a model based on similar rest-phase — motion phase considerations. However, they used different assignments of the probabilities. 

The action potential has been divided into five phases, rapid depolarization (phase 0), early repolarization (phase 1), plateau (phase 2), rapid repolarization (phase 3) and finally the resting phase in myocytes or slow diastolic depolarization (phase 4). The last is a property in cells with the potential for automaticity (defined later). A brief outline of each of these phases in the normal myocyte is given next. 

Unfortunately, many human cancers have a large proportion of cells in the resting phase, and these cells are also resistant to the class 3 agents, which include cyclophosphamide, dactinomycin, and fluorouracil. 

Fig. 14.L Division activity and fate of a cell. Cells can move from a division-active state to a differentiated state or into the resting phase Go. The transition into Go phase is generaUy reversible, whereas differentiated cells often cannot return to the division-active state. The cell can be directed from all three stadia into programmed cell death, or apoptosis.

In the absence of external mitogenic signals or in the presence of a majority of antimi-togenic signals, cell division activity may be stopped. The cell enters the resting phase (Go phase). From Go phase, cell division may be resumed when mitogenic signals reappear. 

To answer this question we need to look more closely at the sleep side of depression. There are three parts to the main story. The first is that many depressives have a markedly reduced time to onset of the first REM period after falling asleep. This tendency to enter REM rapidly is measured as REM latency. The second part is that depressives may also have a marked reduction in time spent in stages III and IV, the deepest and most restful phase of NREM sleep. That could be one reason that their sleep is so unrefreshing. The third reason is that the first REM period is often longer—and stronger—than is seen in age and sex matched normal controls. These processes are represented in terms of the AIM state space model as figure 11.1. 

Fig- 35. The in-plane magnetostriction Ay, coercivity HqHc and Curie temperature Tq as a function of the annealing temperature Ta for TbDyFe + Zr/Nb multilayers. Open square symbols indicate the phase transition temperature of an amorphous rest phase. After Fischer et al. (1999). 

After a long fallow period, other workers have recently begun to extend Challenger s arsenic biomethylation work (1-3). Cox and Alexander have studied this reaction by the mold Candida humicola (59-9/). The overall reaction may be summed up by the reaction shown in Eq. (6). Both cell extracts and whole cells of Methanobacterium strain M.o.H. converted arsenate to dimethylarsine (92). Investigations on C. humicola and other molds determined that the rate of (CH s production follows the growth rate pattern of the mold, and decreases when the mold reaches the resting phase (93). The methylated arsenic intermediates were identified by use of... 

There has been concern at various times that prolonged oral contraception might cause permanent changes in the genital system. When high-dose products were in use, various studies showed condensation of the superficial cortical layers of the ovary (SEDA-8, 863). Severe atrophy of the endometrium after a period of oral contraception has been described (267), but the report usually quoted is one that dates from a period when high doses were in use, and the incidence is not known, since the endometrium is not usually examined. Certainly, the endometrium will go into a resting phase in women who have amenorrhea, but there is no reason to believe that it will become permanently unresponsive. 

A hair shaft contains little or no DNA. The major source of DNA from hair is the hair root pulled from the scalp. The hair that sheds by itself or comes out easily on pulling from the scalp is most likely from the resting phase of the hair follicle and is not a good source of DNA, as it contains mostly cellular debris at its root. However, it is possible to isolate DNA from pulled hair roots [24]. 

At the end of the effective stroke the cilium disengages from the mucus gel and enters the rest phase where it lies parallel to the epithelium pointing in the direction of mucus flow. This position is believed to discourage any reversal of mucus movement. 

---