Environmental cues

Cells communicate with each other in order to form and maintain the vertebrate body. Cells must know when and where to move, and what to do once they get there. This is accomplished by sending and receiving chemical, tactile, and perhaps even electrical signals (Cooper and Schliwa, 1986). Cells can be observed responding to at least some of these environmental cues in tissue culture, and also responding to each other. The response of cells to these factors is known as cell behavior. 

Prokaryotic genes are often regulated in an on-off man-net in tesponse to simple environmental cues. Some eu-katyotic genes are regulated in the simple on-off man-... 

Vertebrate development reflects the other extreme of the genetic/epigenetic continuum unlike invertebrates, numerous environmental cues are employed to direct lineage decisions, including the decisions for survival,... 

Negus, N. C. and Berger, P. J. (1988) Cohort analysis environmental cues and diapause in microtine rodents. In M.S. Boyce (Ed.), Evolution of Life Histories of Mammals, Theory and Pattern. Yale University Press, New Haven, pp. 65-1 A. 

Regulation of transcription is a central mechanism by which cells respond to developmental and environmental cues. RNA polymerase Il-mediated transcription in eukaryotes is to a large extent regulated at the level of chromatin, which forms a physical barrier for the binding of proteins to the promoter region of a target gene. The basic unit of chromatin is the nucleosome, which consists of an octamer of histone proteins around which the DNA is wrapped (see Fig. la). 

Environmental cues associated with drug intake play a substantial role in the maintenance of habits and contribute to relapse (Abrams et al. 1988). The traditional model of addiction emphasizes affect, whereby drug-related cues trigger feelings of... 

Kaye, H., Mackintosh, N. J., Rothschild, M., and Moore, B. P. (1989). Odour of pyrazine potentiates an association between environmental cues and unpalatable taste. Animal Behaviours , 563-568. 

B. The lac operon of E coli is a good model for regulation of prokaryotic gene expression in response to environmental cues (Figure 12-4). 

The ability of a cell to respond to environmental cues is critical for its survival. Signals arrive from neighboring cells or are transported in the blood and instruct the cell to proliferate, to differentiate into new cell types, or even to die in a normally occurring process termed apoptosis. Cells must be able to receive these signals, interpret them correctly, and respond to the sig-... 

Conceptually, tics are best seen as senseless habits that arise in response to a highly selective set of somatic and/or environmental cues. Habits, like tics, are assembled routines that link sensory cues with motor action. The neural substrates of habit formation and tics are neural loops that connect the basal ganglia with the cortex and thalamus (Fig. 13.1 Graybiel, 1998 Leck-man and Riddle, 2000). 

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