Tissue processing Chapter

This technique is required for any embryo-fetal developmental toxicity in the rat, mouse, rabbit, or minipig. Caesarean sections are performed on dams before birth. Fetuses are removed and examined externally. Further examinations are then performed to examine internal soft tissues (see Chapters 19 and 20) and skeleton. Fetuses intended for skeletal examinations are eviscerated and the carcasses are fixed. The Alizarin Red S staining process requires several days. The meticulous examination involves the examination of each fetal in a specific order starting from the head to the tail, with the fetus in ventral and dorsal positions. 

Chapter 2 How Different Tissues Process Drug Response... 

Phospholipids and glycosphingolipids are amphipathic lipid constituents of membranes (Chapter 10). They play an essential role in the synthesis of plasma lipoproteins (Chapter 20) and eicosanoids (Chapter 18). They function in transduction of messages from cell surface receptors to second messengers that control cellular processes (Chapter 30) and as surfactants. Cholesterol is mainly of animal origin and is an essential constituent of biomembranes (Chapter 10). In plasma, cholesterol is associated with lipoproteins (Chapter 20). Cholesterol is a precursor of bile acids formed in the liver of steroid hormones secreted by adrenals, gonads, and placenta and 7-dehydrocholesterol of vitamin D formed in the skin. In tissues, cholesterol exists primarily in the unesterified form (e.g., brain and erythrocytes), although appreciable quantities are esterified with fatty acids in liver, skin, adrenal cortex, and plasma lipoproteins. 

Amylases act on glycogen in a manner closely similar to that on amylopectin (see under Starch). As the storage product of carbohydrates in the animal body, glycogen is in eqxiilibrium with other tissue components through the metabolic processes (Chapter XIII). 

Once the basic metabolic pathways have been considered, the book continues with Section 5, Control Processes, which covers regulatory mechanisms operating within the cell and also the hormones responsible for integrating the body s various component systems. Section 6 on Soft Tissues contains chapters on body fluids, epithelium and connective tissue and deals with areas rarely covered in detail in textbooks of biochemistry. 

The processes of electron transport and oxidative phosphorylation are membrane-associated. Bacteria are the simplest life form, and bacterial cells typically consist of a single cellular compartment surrounded by a plasma membrane and a more rigid cell wall. In such a system, the conversion of energy from NADH and [FADHg] to the energy of ATP via electron transport and oxidative phosphorylation is carried out at (and across) the plasma membrane. In eukaryotic cells, electron transport and oxidative phosphorylation are localized in mitochondria, which are also the sites of TCA cycle activity and (as we shall see in Chapter 24) fatty acid oxidation. Mammalian cells contain from 800 to 2500 mitochondria other types of cells may have as few as one or two or as many as half a million mitochondria. Human erythrocytes, whose purpose is simply to transport oxygen to tissues, contain no mitochondria at all. The typical mitochondrion is about 0.5 0.3 microns in diameter and from 0.5 micron to several microns long its overall shape is sensitive to metabolic conditions in the cell. 

The remainder of this chapter will deal with natural polymers. These are large molecules, produced by plants and animals, that carry out the many life-sustaining processes in a living cell. The cell membranes of plants and the woody structure of trees are composed in large part of cellulose, a polymeric carbohydrate. We will look at the structures of a variety of different carbohydrates in Section 23.3. Another class of natural polymers are the proteins. Section 23.4 deals with these polymeric materials that make up our tissues, bone, blood, and even hair. ... 

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