Investigations on the mitochondria of the housefly, Musca domestica L. III. Requirements for oxidative phosphorylation

Proteomic profile of mouse fibroblasts exposed to pure magnesium extract

Magnesium and its alloys gain wide attention as degradable biomaterials. In order to reveal the molecular mechanism of the influence of biodegradable magnesium on cells, proteomics analysis was performed in this work. After mouse fibroblasts (L929) were cultured with or without Mg degradation products (Mg-extract) for 8, 24, and 48h, changes in protein expression profiles were obtained using isobaric tags for relative and absolute quantitation (iTRAQ) coupled two dimensional liquid chromatography-tandem mass spectrometry (2D LC MS/MS). A total of 867 proteins were identified (relying on at least two peptides). Compared to the control group, 205, 282, and 217 regulated proteins were identified at 8, 24, and 48h, respectively. 65 common proteins were up or down- regulated within all the three time points, which were involved in various physiological and metabolic activities. Consistent with viability, proliferation, and cell cycle analysis, stimulated energy metabolism as well as protein synthesis pathways were discussed, indicating a possible effect of Mg-extract on L929 proliferation. Furthermore, endocytosis and focal adhesion processes were also discussed. This proteomics study uncovers early cellular mechanisms triggered by Mg degradation products and highlights the cytocompatibility of biodegradable metallic materials for biomedical applications such as stents or orthopaedic implants.

Metabolic pathways in Anopheles stephensi mitochondria

No studies have been performed on the mitochondria of malaria vector mosquitoes. This information would be valuable in understanding mosquito aging and detoxification of insecticides, two parameters that have a significant impact on malaria parasite transmission in endemic regions. In the present study, we report the analyses of respiration and oxidative phosphorylation in mitochondria of cultured cells [ASE (Anopheles stephensi Mos. 43) cell line] from A. stephensi, a major vector of malaria in India, South-East Asia and parts of the Middle East. ASE cell mitochondria share many features in common with mammalian muscle mitochondria, despite the fact that these cells are of larval origin. However, two major differences with mammalian mitochondria were apparent. One, the glycerol-phosphate shuttle plays as major a role in NADH oxidation in ASE cell mitochondria as it does in insect muscle mitochondria. In contrast, mammalian white muscle mitochondria depend primarily on lactate dehydrogenase, whereas red muscle mitochondria depend on the malate-oxaloacetate shuttle. Two, ASE mitochondria were able to oxidize proline at a rate comparable with that of alpha-glycerophosphate. However, the proline pathway appeared to differ from the currently accepted pathway, in that oxoglutarate could be catabolized completely by the tricarboxylic acid cycle or via transamination, depending on the ATP need.

Cell structure and the metabolism of insect flight muscle

The biochemical properties of insect flight muscle were investigated to ascertain the mechanisms whereby energy is made available for the contractile processes. It was found: 1. The endogenous respiration of muscle homogenates was diminished by starving the flies. The substrate for this respiration was probably glycogen. 2. To obtain the maximal rate of oxidation of glucose, the homogenate had to be fortified with inorganic phosphate, Mg ions, ATP, and cytochrome c. The nucleotides, AMP and ADP, were not as effective as ATP. The addition of DPN or TPN was not necessary for this system. 3. Flight muscle homogenates oxidized glycogen, some sugars, and amino acids, as well as the intermediates of the glycolytic and tricarboxylic acid cycles. Other evidence demonstrated the substrate specificity of the muscle. 4. By centrifugation, the muscle homogenate was divided into two fractions: one, a soluble fraction representing the sarcoplasm; the other, the particulate fraction which contained the fibrils and the sarcosomes. 5. The particulate fraction, alone, oxidized all the citric acid cycle intermediates, α-glycerophosphate, phosphopyruvate, and the amino acids, glutamic, proline, and cysteine. Regardless of the substrate, no oxygen uptake was found with the sarcoplasm by itself. 6. A recombination of the sarcoplasm and the particulate component was required for the oxidation of glycogen, the hexoses, and all the phosphorylated intermediates of glycolysis, except phosphopyruvate. 7. Isolated mitochondria accounted for all the enzymatic activity of the particulate fraction. These results demonstrate that the enzymes of intermediate metabolism are localized in the sarcoplasm or sarcosomes. The third cytological entity, the myofibrils, plays no role in the energy-providing scheme. From a functional viewpoint, the sarcoplasm and the mitochondria, in combination, furnish the energy for the actomyosin contraction. The results are discussed in relation to analogous findings in other insects and vertebrates.

The sarcotubular system of frog skeletal muscle. A morphological and biochemical study

In the frog skeletal muscle cell a well defined and highly organized system of tubular elements is located in the sarcoplasm between the myofibrils. The sarcoplasmic component is called the sarcotubular system. By means of differential centrifugation it has been possible to isolate from the frog muscle homogenate a fraction composed of small vesicles, tubules, and particles. This fraction is without cytochrome oxidase activity, which is localized in the mitochondrial membranes. This indicates that the structural components of this fraction do not derive from the mitochondrial fragmentation, but probably from the sarcotubular system. This fraction, called sarcotubular fraction, has a Mg(++)-stimulated ATPase activity which differs from that of muscle mitochondria in that it is 3 to 4 times higher on the protein basis as compared with the mitochondrial ATPase, and is inhibited by Ca(++) and by deoxycholate like the Kielley and Meyerhof ATPase. We therefore conclude that the "granules" of the Kielley and Meyerhof ATPase, which were shown to have a relaxing effect, are fragments of the sarcotubular system. The isolated sarcotubular fraction has a high RNA content and demonstrable activity in incorporating labeled amino acids, even in the absence of added supernatant.

Enzyme changes in flight muscle correlated with aging and flight ability in the male housefly

Magnesium-activated adenosine triphosphatase activity in the giant mitochondria (sarcosomes) of the flight muscle of aging male houseflies decreases concomitantly with failure in flight as reflected in the loss of wings during the second week of adult life. Preceding the loss of wings, however, there is a rapid decline in the activity of an alpha-glycerophosphate dehydrogenase which is located in the extramitochondrial fraction and is dependent on nicotinamide adenine dinucleotide.

Atherogenesis and fibrinogen: historical perspective and current status

A review of 117 research publications describes a deficiency in fatty acid transport into intracellular oxidative energy metabolism which causes increased fibrinogen synthesis and turnover into fibrin. The increased production of fibrin, coupled with depressed activation of plasminogen, increases the fibrin/plasmin ratio causing thrombosis-induced atherogenesis. This discovery unifies the two schools of atherogenesis based on blood lipid or fibrin deposition theories.

Hamster brown-adipose-tissue mitochondria. The role of fatty acids in the control of the proton conductance of the inner membrane

The specific ability of fatty acids to increase the proton conductance of the inner membrane of mitochondria from the liver and brown adipose tissue of cold-adapted hamsters was compared. The liver and brown-adipose-tissue mitochondria had their effective proton conductances increased by respectively 0.028 and 0.94 nmol H+- min-1. (mV of proton electrochemical gradient)-1 for each nmol of palmitate bound. No difference could be detected between the abilities of liver and brown-adipose-tissue mitochondria to bind fatty acids. Purine nucleotides did not displace farry acids from the brown-adipase-tissue mitochondria. The endogenous fatty acid content of hamster brown-adipose-tissue mitochondria prepared in the absence of album was found to be equivalent to 17 +/- 7 nmol of palmitate/mg protein. The fatty acid content was reduced to 1 nmol/mg after preincubation of the mitochondria with CoA, ATP and carnitine. No inert pool of fatty acids could be detected. The endogenous fatty acids of hamster liver mitochondria were less than 4 nmol of palmitate equivalent/mg protein. Some of the fatty acid associated with the brown-adipose-tissue mitochondria originates during preparation of the mitochondria. In the light of these results, the physiological role of the fatty acids in controlling the proton conductance of the brown-adipose-tissue mitochondrial inner membrane, and hence- non-shivering thermogenesis, is re-evaluated.

Zonation of the adrenal cortex. II. Effect of BSA on coupling efficiency of mitochondria isolated from the zona glomerulosa of the bovine adrenal cortex

Effect of bovine serum albumin on coupling efficiency of mitochondria isolated from the zona glomerulosa of the bovine adrenal cortex in various media was examined polarographically and electron microscopically. Albumin restored the coupling efficiency of mitochondria isolated from the zona glomerulosa regardless of isolation media when succinate or malate was oxidizable substrate. Respiratory controls greater than 5 were obtained. Albumin, however, had no effect when glutamate, beta-hydroxybutylate and pyruvate were the oxidizable substrates. The conditions have been found under which mitochondria of the zona glomerulosa stay in the orthodox configuration and yet coupled.

Oxidative phosphorylation by muscle mitochondria of dysstrophic mice

Oxidative phosphorylation was studied in mitochondria isolated from the skeletal muscle of control and dystrophic mice of the Jackson Laboratory strain 129/Re, aged 32–104 days. The isolation procedure included a preliminary incubation of the muscle minced in a medium containing a proteinase (Nagarse) followed by gentle homogenization and differential centrifugation. Polarographic estimations in the presence and absence of adenosine diphosphate (ADP) indicated that the rate of oxygen uptake, ADP/0 ratio, respiratory control ratio, and phosphorylation rate were not significantly different in the mitochondria isolated from control and dystrophic mice. Bovine serum albumin increased the ADP/0 and respiratory control ratios, but the values for the control and dystrophic preparations again did not differ significantly in the presence of albumin.

Oxidative phosphorylation and respiratory control in mitochondria from Aspergillus niger

1. Tightly coupled mitochondria were isolated from Aspergillus niger by using an all-glass homogenizer followed by differential centrifugation. 2. The mitochondria oxidized the common intermediates of the tricarboxylic acid cycle, NADH(2) and the ascorbate-tetramethyl-p-phenylenediamine system. 3. High P/O ratios and control of respiration by ADP were obtained with all substrates tested. The average P/O ratios observed were: 1.5-1.8 with succinate as substrate [respiratory control ratio (RC) 2-4]; 0.8-1.0 with ascorbate-tetramethyl-p-phenylenediamine (RC 1.2-1.5); 1.4-1.8 with NADH(2) (RC 2-3); 2.4-2.8 with alpha-oxoglutarate (RC 3-5). 4. Bovine serum albumin (0.05-0.2%) was essential for tightly coupled respiration to be observed. 5. Coupled oxidation of exogenous NADH(2) was relatively insensitive to rotenone and Amytal. 6. The mitochondria responded to specific inhibitors and uncoupling agents in a manner similar to that of mammalian mitochondria. 7. It was concluded that the isolated mitochondria from A. niger show respiratory properties similar to those reported for intact yeast and mammalian mitochondria.

Aldolase activity in confused flour beetle, Tribolium confusum Duval (Tenebrionidae, Coleoptera)

Certain biochemical characteristics of aldolase in Tribolium confusum homogenate have been determined. The Michaelis constant (Km) has been calculated to be 1.2 × 10−3 M. The effect of various inhibitors suggests that T. confusum aldolase resembles muscle aldolase.Intracellular localization of the enzymatic activity shows that aldolase is contained mainly in the soluble fraction and to a less extent, in an unbound form, in nuclei.Aldolase activity has been demonstrated in relation to various stages in the life cycle of this insect. Such a study reveals that the Embden-Meyerhof glycolytic pathway is not a prominent energy-yielding pathway in T. confusum.