Tissues chemical changes

Active hyperemia. The increase in blood flow caused by enhanced tissue activity is referred to as active hyperemia. Assuming a constant blood pressure, then according to Ohm s law (Q = AP/R), the increase in blood flow is the result of a decrease in local vascular resistance. Tissue metabolism causes several local chemical changes that can mediate this metabolic vasodilation. These include ... 

Each of these chemical changes promotes vasodilation of arterioles. In addition, the increase in tissue temperature associated with increased metabolism further contributes to metabolic vasodilation. The resulting increase in local blood flow restores these substances to their resting values. More oxygen is delivered and excess carbon dioxide, hydrogen and potassium ions, and adenosine are removed. 

With the exception of Buchner s yeast extract and some comparable muscle preparations (Chapter 4), disrupting tissues often caused such damage to cells that normal metabolism was irreversibly affected. A further obstacle was that classical methods of analysis were neither sufficiently sensitive, rapid nor simple enough for the multiple measurements required to follow chemical changes in small samples of tissue. 

The chemical changes that take place in detached fruit are directly, or indirectly, related to the oxidative and fermentative activities collectively referred to as biological oxidations. Once the fruit is harvested, respiration, the process concerned with the oxidation of predominantly organic substances by the cell, assumes the dominant role, and the fruit no longer depends on absorption of water and minerals by the root, on conduction by vascular tissues, and on the photosynthetic activity of the leaves. After harvest, the fruit lives an independent life by utilizing substrates accumulated during maturation.385... 

The fat-soluble vitamins can be extracted from the food matrix without chemical change using a solvent system that is capable of effectively penetrating the tissues and breaking lipoprotein bonds. A total lipid extraction is required for the simultaneous determination of vitamers or vitamins with a wide range of polarities, and, for this purpose, a mixture of chloroform and methanol (2 + 1) is highly efficient (82). The Rose-Gottlieb method is particularly suitable for ex-... 

The development of the types of skeletons that characterize Tommotian faunas constituted a major evolutionary event. Although skeletons are known to support soft tissue and to facilitate locomotion, such adaptive functions cannot explain why so many different kinds of skeletons developed suddenly in the early part of Tommotian time. It has been suggested that a chemical change within the oceans triggered the production of these skeletons, but this hypothesis does not explain why some skeletons were composed of calcium carbonate and others of calcium phosphate, two compounds with quite different chemical properties. The rapid evolution of various kinds of external skeletons is probably in part attributable to the fact that animals... 

FPA imaging and spectroscopy for monitoring chemical changes in tissue... 

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