Tissues mitochondria

Thiolester hydrolases are present in most tissues and cell compartments. High concentrations are found in liver microsomes and in brown adipose tissue mitochondria and peroxisomes. Several acyl-CoA hydrolases have shown a close relationship to the nonspecific carboxylesterases EC 3.1.1.1. Thus, palmitoyl-CoA hydrolase purified from rat liver microsomes was found to be identical to esterase pI 6.2I6A (ES4 type). An acyl-CoA hydrolase was isolated that showed high similarity to esterase pI 6.1 [74a] [129] [130]. These few examples are further illustrations of the unsatisfying situation of the traditional classification of esterases. 

The first defect, described in 1962 is, in fact, one of the rarest (Luft s syndrome). It arises from the uncoupling of mitochondria. The resting metabolic rate is markedly raised, there is profuse sweating, fever and generalised muscle weakness. The mitochondria of these patients have an increased permeability, not so much to protons, as in brown adipose tissue mitochondria, but to cations, such as Ca, the entry of which similarly dissipates the proton motive force. 

Emeretli, I.V. (1981b). Activity of succinate dehydrogenase in tissue mitochondria of Black Sea fishes (In Russian). Ekologiya Morya 1981 (7), 60-63. 

Malan, A., and E. Mioskowski (1988). pH-tempera-ture interactions on protein function and hibernation GDP binding to brown adipose tissue mitochondria. J. Comp. Physiol. B. 158 487-493. Martin, D.D., R.A. Ciulla, and M.F. Roberts (1999). Osmoadaptation in Archaea. Appl. Environ. Microbiol. 65 1815-1825. 

S. E. Mansurova, Yu. A. Shakhov and I. S. Kulaev (1973b). The coupling of inorganic pyrophosphate synthesis with respiration in animal tissue mitochondria (in Russian). Dokl. Akad. Nauk SSSR, 213, 1207-1209. 

Within the last decade we have obtained a tentative concept of the molecular basis for this mammalian mitochondrial thermogenesis, and we know that in contrast to the thermogenic plant mitochondria, substrate oxidation in brown adipose tissue mitochondria is basically energy conserving, with proton extrusion occurring [5], with respiratory control, and with an ability, in principle, to capture the chemical energy in the form of ATP. 

In this review we have not attempted to provide a historical account of the development of this concept (for such an account see Ref. 6), but rather attempted to show how this concept has enabled a series of apparently disparate observations on brown adipose tissue mitochondria to be unified. 

This review is updated to autumn 1983. For other reviews of brown adipose tissue mitochondria see Refs. 7-9, for a review on the integration of mitochondrial function in the brown fat cell see Ref. 3, and for the function of brown adipose tissue as such, see e.g., Refs. 4, 10-12. 

With our present understanding, the thermogenic qualities of brown adipose tissue mitochondria are a consequence of the existence in the mitochondrial inner membrane of a polypeptide, thermogenin, uniquely [13-15] found in brown adipose tissue. (For technical and historical reasons, thermogenin is also known under several other names, such as the GDP-binding protein, the 32000 protein, the purine-nucleotide-binding protein (NbP), the uncoupling protein (UCP), the proton conductance pathway, etc.)... 

The uncoupled state of traditionally isolated and tested brown adipose tissue mitochondria... 

Fig. 10.6. The effect of respiration and membrane potential (Ai )) on Cl permeation in brown adipose tissue mitochondria. When brown fat mitochondria were incubated in KCl in the presence of the ionophore, nigericin, they swelled (A, B). If a respiratory substrate (here G-3-P glycerol-3-phosphate) was added to the expanded mitochondria, they contracted, and this contraction ceased immediately and swelling was reintroduced if azide (NaNj) and an uncoupler (FCCP) were added (Fig. A). The passive halide ion permeability can be inhibited by GDP (cf.. Fig. 10.5), but respiration-driven contraction in KCl-expanded mitochondria was only partially inhibited by the presence of GDP (Fig. B) if again azide and uncoupler were added during the contraction, the mitochondria did not swell, indicating that the thermogenin channel was closed by GDP. This behaviour can partly be explained by the fact that the Cl permeation is driven by the membrane potential. Indeed, when, under similar conditions, the rate of contraction was plotted as a function of the membrane potential, it was seen that the rate was membrane potential dependent. It should, however, he noted that at low membrane potentials GDP nearly totally abolished the Cl permeation but when the membrane potential was increased above 30 mV, the inhibitory effect of GDP was apparently partially lost. The basis for this phenomenon is not understood it is not even known if there is a lower affinity of thermogenin for GDP in the energized membrane, as measurements of GDP affinities always refer to the non-energized situation. (Adapted from Nicholls et al. [27] (A, B) and Nicholls [94] (C).)...

Fig. 10.10. Determination of thermogenin amount in brown adipose tissue mitochondria by the enzyme-linked immunosorbent assay (ELISA) system. The amount of thermogenin was determined as elsewhere described (Cannon et al. [13] Sundin et al. [40] Hansen et al. [56]) in an assay system based on the competition between absorbed and added thermogenin for rabbit on/r-rat-thermogenin antibodies. The interaction was followed with a sheep onri-rabbit-IgG antibody conjugated to alkaline phosphatase. The reaction was linearized as indicated (abs 0 is the absorbance developed in the absence of competing thermogenin). It is seen that this assay can detect less than 0.25 fig thermogenin, i.e., the content in less than 10 fig of mitochondria. It is also seen that the thermogenin content of rat brown fat mitochondria is approximately doubled after a 24 h cold stress. (Our unpublished observations.)...

Fig. 10.11. The effect of osmolarity on the apparent number of GDP binding sites in brown adipose tissue mitochondria. The number of GDP-binding sites was measured in mitochondria from control and cold-exposed (24 h at 4°C) rats as earlier described (Sundin and Cannon [37]), but in media with the indicated concentrations of sucrose. Note that, if iso-osmotic sucrose is used (250 mM), a low GDP binding can be observed, especially in control rats. This may be related to the condensation phenomenon discussed in section 2.4. However, if 100 mM sucrose is used, the mitochondria swell, and the full number of binding sites is determined. (Our unpublished observations.)...

Miro carried out experiments using human muscle tissue. Mitochondria were isolated and each complex of the mitochondrial... 

Mukerji,S.K., Ting, I. P. Malate dehydrogenase (decarboxylating) (NADP) isoenzymes of Opuntia stem tissue. Mitochondria, chloroplast, and soluble forms. Biochem. Biophys. Acta ]67,239-249 (1968 a)... 

Staining Applications Cells gelatin lysosomes mammalian tissues mitochondria neurons nucleic acids proteins urine ... 

In lipid metabolism the turnover of triacylglycerols in adipose tissue has been examined as a possible substrate cycle but it is difficult to see how this could be quantitatively important. Much attention has been focused on brown adipose tissue, since it is known to be important in the generation of heat to maintain body temperature in new-born animals (Figure 5.23). Brown adipose tissue mitochondria are able to generate large quantities of heat because electron transport is largely uncoupled from oxidative... 

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