Muscle water content

Despite their successful use for at least 20 years, the mechanisms by which they lower the blood pressure remain uncertain. Theories to explain the antihypertensive effectiveness of the diuretic agents have included a) alteration of sodium and water content on arterial smooth muscle, b) the induction of a decreased vascular response to catecholamines, c) a decrease in blood volume and total extracellular fluid volume, and d) a direct vasodilator action independent from the diuretic effect(12). 

If the salt content is reduced in muscles so is the water content. This means catabolism, flat muscles come show time, and a lack of vascularity. (It would inhibit erectile function also, but that is another issue all together.)... 

Laboratory experiments showed that the water content of the muscle of small, immature cod subjected to starvation rose (reflecting protein depletion) from 80% to around 86%, beyond which level the fish died. Larger fish, however, which had spawned several times, could be depleted until the water content of the musculature was over 95% - a remarkable adaptation to the more severe depletion imposed under natural conditions (Love, unpublished). While this phenomenon differs from that described above in fatty fish, it again illustrates a change in the metabolism of fish in response to growth. Likewise, Borisov and Shatunovsky (1973) studied the possibility of using the water content to estimate the natural mortality rate of Barents Sea cod. 

Small volume of yellow bile, low value of acid phosphatase, muscle protein normal, water content down to fed values, liver lipid reduced -recovery almost complete. 

Determinations of protein are relatively slow, but a protein-water line has been described (Love, 1970, Figure 85) in the muscle of Atlantic cod, a non-fatty species (r = -0.63). The water content (derived from the dry weight) therefore gives a reasonable estimate of the protein content of this and other non-fatty species. 

Figure 7 6 Relationship between the optical density (as in Figure 75) and the water content of cod white muscle caught at different times of the year. (After Love, 1962.)...

Love, R.M. (1960). Water content of cod (Gadus callarias L.) muscle. Nature, Lond. 185,692. 

Shatunovsky, M.I. (1963). Dynamics of fatness and water content in muscles and gonads of Baltic flounder as related to gonad maturation (In Russian). Voprosy Ikhtiologii 3,652-667. 

The amount of tightly bound water (water of hydration) present in the myoglobin solution can be calculated from the amplitude of the S dispersion using a method previously described (1,10). From the value of 3.6 for this parameter (Table I) a value of hydration of 0.15-0.02 unit mass of water per unit mass of myoglobin is obtained. Considered as a volume fraction of the total water content this would amount to about 4%, which compares well with the figure of 5% recently proposed for muscle fibres by Foster, Schepps and Schwan (16). 

The lipid, water, and protein contents of certain tissues vary markedly as a function of age. For example, the adipose tissues of neonates contain about 55% water and 35% lipids, whereas the corresponding figures for the adult are about 25% and 70%, respectively (Friis-Hansen, 1971). The proportion of water in skin falls as a function of age, due to an increase in collagen. The water contents of liver, brain, and kidneys decrease from birth to adulthood by 5-15%. The decrease in water contents of liver and kidneys is primarily due to an increase in protein, whereas this change in the brain is due to an increase in myelin. The overall composition of muscle in terms of lipid and water does not seem to vary with age (Dickerson Widdowson, 1960). 

Although zooplankton tend to maintain a rather rigid biochemistry, intra- and interspecific differences may arise due to physical characteristics (e.g., water content, body size), developmental stage, as weU as location (e.g., latitude) and season. Increased water content, and thus decreased muscle tissue, leads to a decrease in protein and N content in zooplankton (ChUdress and Nygaard, 1974 Morris and Hopkins, 1983). This may explain the lower N and protein content in gelatinous zooplankton relative to crustaceans as described above. The effect of water content on proteins can also be seen within taxonomic groups. For example, Calanus paciftcus... 

Skeletal muscle is a major component of body tissue and accounts for 40-50% of the body weight. Skeletal tissue is composed of specialized striated cells, which function to convert chemical energy to mechanical work. Skeletal muscle plays a central role in body metabolism and serves as a source of body heat and a storage depot for energy-rich compounds, protein, and intracellular ions (e.g., potassium). It also contains up to 80% of the body water content. In contrast to cardiac and smooth visceral muscle tissue, skeletal muscle is under voluntary control. 

The composition of fish striated muscle with respect to water, proteins, and lipids differs widely from one species to another, and within a species seasonal variations may occur. The influence of this factor has been investigated by Van Wyk (1944). In fatty fishes, an important increase in fat content is observed in Spring or in Summer, with a corresponding decrease in water content, while the nitrogen values remain relatively constant. Determinations made on many species by various authors have been compiled by Jacquot and Creac h (1950). Other evaluations have been done more recently on numerous Spanish fishes (De Las Heras and Mendez Isla, 1952) on a few Kolhapur fresh-water fishes (Airan and Joshi, 1952), and on Skipper Cololabis saira) (Tsuchiya et ah, 1953). Some of the figures given by Jacquot and Creac h (1950) are reproduced in Table I, which contains for each species a mean value or sometimes two values corresponding to the limits of variation. Water accounts for three-... 

LEDWARD, D. A. (1971). Metmyoglobin formation in beef muscles as influenced by water content and anatomical location. J. Food. Sci., 36, 138-140. 

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