How do I determine what cells are secreting a soluble substance within a tissue?

I think it depends on the nature of the cell population to investigate (whether is is "mobile" or bound to a body mass. The general idea is to use fluorescent or radioactive dyes that can be monitored with imaging systems in vivo.

A good example is given by Injections of a radioactive dye for sentinel lymph node identification, by the use of a radiolabeled, low molecular weight dye (e.g., .sup.125I-labeled methylene blue). This radiolabled dye is mixed with an unlabeled, similar molecular weight dye (e.g., isosulfan or methylene blue). The mixture is injected at the time of surgery, and rapidly migrates to reach the lymph nodes in less than 20 min, more preferably in less than 15 min and most preferably in less than 10 min.

Optical whole-body imaging techniques can also be used for monitoring normal and leukemic hematopoietic cell homing in vivo. A recently developed near-infrared (NIR) lipophilic carbocyanine dye 1,1[prime]-dioctadecyl-3,3,3[prime],3[prime]-tetramethylindotricarbocyanine iodide (DiR) is used to safely and directly label the membranes of human leukemic Pre-B ALL G2 cell lines as well as primary murine lymphocytes and erythrocytes. DiR has absorption and fluorescence maxima at 750 and 782 nm, respectively, which corresponds to low light absorption and autofluorescence in living tissues. This allows to obtain a significant signal with very low background level. This powerful technique can potentially visualize any cell type without use of specific antibodies conjugated with NIR fluorescent tag or loading cells with transporter-delivered NIR fluorophores.

finally, definite, each and every thing is secreted with the aid of cells. in case you propose, is floor substance secreted with the aid of the cells that it surrounds, the respond is "often" (collagen) yet no longer constantly (a marvelous form of morphogens are created someplace else, then snagged with the aid of purpose cells with the the ideal option extra suitable-cellular membrane proteins). The term "floor substance" isn't utilized in modern-day biology. often we communicate bearing directly to the "extracellular matrix" or "basement membrane"