Differentiation, in the periphery

Nature is economical in her means. She uses many of the same chemicals to accomplish her nervous purposes within the brain that she has already used to the same ends throughout the body. The good news is that once you have worked out the biochemistry and pharmacology of a neuromodulator in the body, you can apply a lot of what you know to its action in the brain. The bad news is that every time you target, for example, the acetylcholine system of the brain, you also hit the body. That means that the heart, the bowel, the salivary glands, and all the rest of the organs innervated by the autonomic nervous system are influenced. What is worse, the target sites within the brain may not only be as spatially dispersed as in the periphery, but may also be as functionally differentiated ... 

Large cell carcinomas are anaplastic tumors that show no evidence of differentiation. These tumors account for only about 15% of all lung cancers. These tumors tend to be large and bulky tumors arising in the periphery of the lung, to have a propensity to metastasize in a pattern quite similar to adenocarcinomas, and to be associated with a similar poor prognosis. 

Development and differentiation of T cells in thymus, spleen, or lymph nodes is assessed by T cell surface markers (see Chapters 2.3 and 3.2). Some T cell surface markers can also be used to examine T cell function. For example, the population of CD4p° /CD62L iow/cD44 s is considered memory T cells, whereas cD4p° 7CD25p T cells are considered regulatory T cells in the periphery. 

At the stem apex, alkaloids are present in all the young undifferentiated cells. According to Molle (6), the most recently formed cells have comparatively little, the precipitations increasing to a maximum density at a short distance behind the actual apex. The zone of tissue differentiation is also abundantly supplied, but as differentiation proceeds, alkaloids disappear from the vascular strands, and then from the central tissues of the pith. When differentiation is complete, the alkaloids are located principally in three concentric layers, in the epidermis and outer cortical layers just below it, in parenchyma within and adjacent to the phloem, and in the periphery of the pith just inside the xylem strands. The xylem parenchyma and medullary rays also possess alkaloids after they have disappeared from the conducting elements. 

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