Metabolic change

Another widely used approach to the elucidation of metabolic sequences is to feed cells a substrate or metabolic intermediate labeled with a particular isotopic form of an element that can be traced. Two sorts of isotopes are useful in this regard radioactive isotopes, such as and stable heavy isotopes, such as or (Table 18.3). Because the chemical behavior of isotopically labeled compounds is rarely distinguishable from that of their unlabeled counterparts, isotopes provide reliable tags for observing metabolic changes. The metabolic fate of a radioactively labeled substance can be traced by determining the presence and position of the radioactive atoms in intermediates derived from the labeled compound (Figure 18.13). 

Measurements of metabolite concentrations in muscle fibers before and after fatiguing stimulation have shown that ATP decreases from 6 to 4.6 mM and PCr decreases from 35 to 2.4 mM with a calculated increase in Pj from 3 to 38 mM (Dawson et al., 1978 Nassar-Gentina et al., 1978). The free ADP concentration was calculated to increase from 30 to 200 pM. At the same time pH decreased from 7.0 to 6.5 (Dawson et al., 1978 Juel, 1988 Westerblad and Lannergren, 1988). The effect of these metabolic changes has been studied in skinned muscle fibers, i.e., fibers in which the cell membrane has been removed. The skinning of the fibers... 

It has been shown that inositol triphosphate (IP3) is involved in the excitation-contraction coupling in smooth muscle (Vergara et al., 1985), but presently no clear evidence has been reported for a similar involvement in skeletal muscle. If IP3 functions as a messenger for Ca release, it would bridge the gap between muscle metabolic changes and Ca release, as ATP is a prerequisite for IP3 regeneration. 

As discussed above, pronounced metabolic changes are associated with the decrease in force during intense exercise. Reasonably good correlations are ob-... 

Edwards, R.H.T., Hill, D.K., Jones, D.A. (1975). Metabolic changes associated with the slowing of relaxation in fatigued mouse muscle. J. Physiol. 251,287-301. 

The dramatic decrease in the morbidity and mortality of HIV-infected individnals in the last decade, due to the wide use of HAART, has been somewhat tempered by the emergence of mid-long term toxicities. A characteristic body fat redistribntion and metabolic changes, inclnding dyslipidemia and insnlin resistance, are amongst the most prevalent and worrisome consequences (Carr et al. 2003). As HIV-infected individnals have increasing life expectancies, the risk for cardiovascnlar complications has emerged as an important canse of morbidity and mortality and preventive measnres should be considered to minimize their impact (Weber et al. 2006). 

Siddiqui MKJ, Anjum F, Qadri SSH. 1987a. Some metabolic changes induced by endosulfan in hepatic and extra hepatic hssues of rat. J Environ Sci Health B22 553-564. 

Barse, A.V., Chakrabarti, T., Ghosh, T.K. et al. (2007). Endocrine disruption and metabolic changes following exposure of Cyprinus carpio to diethyl phthalate. Pesticide Biochemistry and Physiology 88, 36-42. 

A. Massonneau, N. Langlade. S. Leon, J. Smutny, E, Vogt, G. Neumann, and E. Martinoia, Metabolic changes associated with proteoid root development in white lupin (Lupimis aihus L.) relationship between organic acid excretion, sucrose metabolism, and fermentation. Planta. Submitted. 

Subchondral bone undergoes metabolic changes, including increased bone turnover, that appear to be precursors to tissue destruction. The normally contiguous bony surface becomes fissured. Persistent use of the joint eventually results in loss of cartilage, permitting bone-to-bone contact that ultimately promotes thickening and eburnation of exposed bone. Microfractures may appear in subchondral bone, and osteonecrosis may develop beneath the surface. 

Fig. 7. Neurohumoral control of the metabolic changes during the acute phase of septic shock. AVP, vasopressin SNS, sympathetic nervous system TAG, triacylglycerol FFA, free faty acid. (Reproduced with permission from Clin. Endocrinol. K. N. Frayn, 24,577-599, 1986, by copyright permission of Blackwell Science Ltd., Oxford, UK.)...

Brody, A.L., Mandelkem, M.A., London, E.D. et al. Brain metabolic changes during cigarette craving. Arch. Gen. Psychiatry. 59 1162, 2002. 

Relatively less work has been done on immobilization of plant and animal cells and spores of microbes in silica matrixes. The main drawback is less viability of the cells in sol-gel matrices. Thus more refined methods are required to utilize harness of the whole cells entrapped in sol-gel matrices and biosensing applications. At the same time studies such as interactions between sol-gel matrices and whole cells and metabolic changes during immobilization have to be closely monitored for the exploration of new matrices and methods. 

The rate and pathways of metabolism change during development 535... 

Kolko, M., DeCoster, M. A., Rodriguez de Turco, E. B. and Bazan, N. G. Synergy by secretory phospholipase A2 and glutamate on inducing cell death and sustained arachidonic acid metabolic changes in primary cortical neuronal cultures./. Biol. Chem. 271 32722-32728,1996. 

When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A s efficiency, as one of the cells firing B, is increased. ... 

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