Deleterious effects of disulfiram on the respiratory electron transport system of liver mitochondria

• 1.1. The mechanism of action of disulfiram on the respiratory electron transport system of the liver mitochondria was studied in vitro.
• 2.2. Disulfiram inhibited the respiration supported by malate-glutamate as well as succinate.
• 3.3. Mitochondrial respiration inhibition was dependent upon alteration of —SH groups.
• 4.4. The inhibitory action of disulfiram might be related to the crosslinking of several proteins of the inner mitochondrial membrane.
• 5.5. The effects described above could be attributed to disulfiram per se and not to the main metabolite diethyldithiocarbamate.

     

Regulation of rat-kidney cortex fructose-1,6-bisphosphatase activity. II. Effects of adenine nucleotides

• 1.1. The native rat-kidney cortex Fructose-1,6-bisphosphatase is differentially regulated by adenine nucleotides in the presence of divalent cations.
• 2.2. Binding of AMP and ADP to the enzyme is co-operative. The inhibition by both nucleotides show an uncompetitive mechanism AMP being the most efficient inhibitor.
• 3.3. Mg²⁺ decreases the inhibition produced by AMP and ADP by enhancing their I_0.5 and completely annulates the inhibitory effect of ATP.
• 4.4. In the presence of Mn²⁺ ADP behaves as an inhibitor but no inhibition is evident with AMP, suggesting the existence of different allosteric sites for each nucleotide.

     

Sympathoadrenal activity during helox-cold induced hypothermia in syrian hamsters

• 1.1. As reflected by increasing plasma concentrations of cortisol, norepinephrine, epinephrine and dopamine, a marked stimulation of the adrenal cortex and of the sympathetic nervous system occurred in Syrian hamsters during moderate hypothermia induced by helium-oxygen atmosphere and cold.
• 2.2. A profound hyperglycemia was observed during hypothermia.
• 3.3. All effects due to the helium-oxygen atmosphere and cold exposure (helox-cold) disappeared almost completely after rewarming.
• 4.4. The results corroborate the hypothesis of an involvement of the adrenal cortex combined with the sympathetic nervous system in the control of acute induced heat production.

     

Purification and some properties of isocitrate dehydrogenase of a blowfly Aldrichina grahami

• 1.1. NADH-dependent isocitrate dehydrogenase has been purified 110-fold from the crude extract of the flight muscle mitochondria of Aldrichina grahami.
• 2.2. The purification procedure involved Triton X-100 treatment of isolated mitochondria, column chromatography on DEAE-cellulose, Affi-gel blue, and P-cellulose.
• 3.3. The purified enzyme was homogeneous by criteria of the polyacrylamide gel electrophoresis.
• 4.4. The enzyme of the blowfly contains more acidic amino acids and less hydrophobic amino acids than that of pig heart.
• 5.5. The molecular weight was determined to be 330,000 daltons. The subunit construction differs from ghat of mammalian isocitrate dehydrogenase.

     

Evidence for extracellular deamination of adenosine in the rat heart

• 1.1. In rat heart perfused with adenosine (10⁻⁶M), dilazep (10⁻⁴M) inhibited incorporation of adenosine into nucleotides (an index of nucleoside transport and phosphorylation) to a greater extent (70%) than metabolism to inosine and uric acid (40%) and actually increased the recovery of inosine to 30% of the adenosine infused.
• 2.2. Extrapolating for complete inhibition of transport suggested that 60% of adenosine metabolism was intracellular and 40% extracellular.
• 3.3. Static incubations of atria also gave an estimate for extracellular metabolism of 40%.
• 4.4. Adenosine deaminase was localised by immunocytochemistry to the extracellular surface of endothelial cells of small coronary arteries.
• 5.5. Extracellular deamination may explain the lack of effect of nucleoside transport inhibitors on responses to adenosine in rat heart.

     

Oxidative metabolism of the inner and outer ventricular layers of carp heart (Cyprinus carpio L.)

• 1.1. The biochemical characteristics of homogenates and mitochondria isolated from the outer and inner layers of the ventricular myocardium of carp were studied.
• 2.2. The homogenate prepared from the inner layer exhibited higher activity of cytochrome oxidase than that from the outer layer. No difference was found in the activity of cytochrome oxidase between mitochondria from the inner and outer layers. Difference spectra of cytochromes also showed that their content in mitochondria of both layers is similar and that the higher oxidative capacity of the spongious layer is due to a higher content of mitochondria.
• 3.3. In comparison with rat heart a higher content of cyt aa₃ and a lower content of Cyt b and cyt cc₁ were found in carp heart mitochondria.
• 4.4. In comparison with rat heart, carp heart mitochondrial enzymes were more sensitive to freezing-thawing and to detergent action.

     

Effects of the nonsteroidal anti-inflammatory drug piroxicam on energy metabolism in the perfused rat liver

• 1.1. The actions of piroxicam, a nonsteroidal and noncarboxylic anti-inflammatory drug, on the metabolism of the isolated perfused rat liver were investigated. The main purpose was to verify if piroxicam is also active on glycogenolysis and energy metabolism, as demonstrated for several carboxylic nonsteroidal anti-inflammatories.
• 2.2. Piroxicam increased oxygen consumption in livers from both fed and fasted rats.
• 3.3. Piroxicam increased glucose release and glycolysis from endogenous glycogen (glycogenolysis).
• 4.4. Gluconeogenesis from lactate plus pyruvate was inhibited.
• 5.5. The action of piroxicam on oxygen consumption was blocked by antimycin A, but not by atractyloside.
• 6.6. The action of piroxicam in the perfused rat liver metabolism seems to be a consequence of its action on mitochondria.
• 7.7. It can be concluded that inhibition of energy metabolism and stimulation of glycogenolysis are not specific properties of carboxylic nonsteroidal anti-inflammatory drugs.

     

Effect of methyl methacrylate on mitochondrial function and structure

• 1.1. Treatment of isolated rat liver mitochondria with methyl methacrylate (MM) produced membrane disruption as evidenced by the release of citrate synthase, and changes in the ultrastructure of mitochondria.
• 2.2. At concentration 0.1%, MM uncoupled oxidative phosphorylation as evidenced by stimulation of state 4 respiration supported either by pyruvate plus malate or succinate (+rotenone) and ATP-ase activity in intact mitochondria.
• 3.3. At concentration 1% MM stimulated ATP-ase activity in intact mitochondria and succinate (+rotenone) oxidation at state 4 and was without effect on this substrate oxidation at state 3.
• 4.4. MM inhibited pyruvate plus malate oxidation either at state 3 or in the presence of uncoupling agents.
• 5.5. MM inhibited the NADH oxidase of electron transport particles at a concentration which failed to inhibit either succinic oxidase or the NADH-ferricyanide reductase activity.
• 6.6. The data presented suggest that in the isolated mitochondria MM inhibits NADH oxidation in the vicinity of the rotenone sensitive site of complex I.
• 7.7. The general conclusion is that MM may block an electron transport and to uncouple oxidative phosphorylation in rat liver mitochondria. The overall in vitro effect would be to prevent ATP synthesis which could result in cell death under in vivo conditions.

     

Rapid preparation of subsarcolemmal and interfibrillar mitochondrial subpopulations from cardiac muscle

• 1.1. Subsarcolemmal and interfibrillar mitochondria were prepared with complete recovery from rabbit and porcine heart muscle by upward-flotation during 60 sec of Percollö density gradient centrifugation.
• 2.2. Mitochondrial subpopulations were identified and characterized according to buoyant density, electron-microscopy, marker enzyme activities and respiratory performance.
• 3.3. ADP-induced state 3-respiration related to latent citrate synthase activity as a marker for structurally intact mitochondria was not significantly different in both mitochondrial subtypes.

     

Protein tyrosine phosphorylation in normal rat tissues

• 1.1. Exogenous and endogenous tyrosine protein phosphorylation activities were examined in soluble and partieulate fractions from various normal tissues by using poly-[Glu-⁸⁰Na, Tyr²⁰] and a monoclonal antibody specific for phosphotyrosine.
• 2.2. Phosphorylation of the exogenous substrate by the partieulate forms of TPKs was 2- to 10-fold higher than by soluble forms. The activities of partieulate and soluble enzymes decreased in the following order: spleen > (thymus = kidney) > testes ⩾ (pancreas = liver = brain) > heart.
• 3.3. The level of endogenous phosphorylation in the tissues decreased respectively in the following order: thymus > brain ⩾ (pancreas = liver) > spleen > testes > kidney > heart for the partieulate fractions, and spleen > thymus > brain > pancreas ⩾ liver > testes > kidney > heart for the soluble fractions.
• 4.4. A large number of phosphotyrosine-containing proteins were detected. In addition, several phosphotyrosine-containing proteins of similar molecular weight were found in different tissues and fractions.

     

Tissue lipoperoxidation and glutathione peroxidase activity in puromycin aminonucleoside injected rats

• 1.1. Lipoperoxidation (LPx) and glutathione peroxidase (GPx) activity were measured in kidney, liver, heart, lung, brain and testis from control and puromycin aminonucleoside (PAN) injected rats on days 1–6, 8, 10, 16 and 22 after vehicle or PAN injection.
• 2.2. PAN-injected rats developed proteinuria on day 3.
• 3.3. In PAN-injected rats: (a) LPx increased in kidney, liver, lung, brain and testis before day 3 and in heart on day 3; (b) GPx activity increased in kidney, liver, heart, lung and testis and diminished in brain on day 3 or after.

     

The mechanism of calcium-dependent activation of respiration of liver mitochondria from hibernating ground squirrels,Citellus undulatus

• 1.1. It is shown that Ca²⁺-dependent activation of respiration of liver mitochondria from hibernating ground squirrels is accompanied by mitochondrial swelling.
• 2.2. The swelling of mitochondria from hibernating ground squirrels, as well as the activation of mitochondrial respiration, is precluded by cyclosporin A, p-bromphenacylbromide and oligomycin. Carboxyatractiloside, on the contrary, under these conditions favors the swelling and the acceleration of respiration.
• 3.3. It was concluded that Ca²⁺-dependent activation of hibernating ground squirrel liver mitochondrial respiration resulted from the appearance of a non-specific permeability pathway and from swelling of mitochondria.

     

Osmotically-induced volume changes in isolated cells of a pond snail

• 1.1. To assess whether the stretch-activated (SA) channels in snail cells could contribute to osmoregulation, information is needed about the behaviour of the cells under anisosmotic conditions.
• 2.2. Cells of Lymnaea stagnalis were therefore examined during acute hyposmotic stress (HOS).
• 3.3. Kidney, heart and neuronal cells (monitored photographically) swelled less than expected for strictly semipermeable cells, but exhibited no regulatory volume decrease.
• 4.4. Long-term viability of the cells was not compromised following acute hyposmotic stress.
• 5.5. Quinidine, which blocks SA channels in Lymnaea, intensified stress-induced swelling most markedly in kidney cells.
• 6.6. The data can, however, be explained without invoking recruitment of SA channels.

     

Presynaptic modulation of sensory afferents in the invertebrate and vertebrate nervous system

• 1.1. Ultrastructural examination of the central terminals of sensory afferent neurons in both invertebrates and vertebrates demonstrates that the synapses that form the substrate for presynaptic inhibition and facilitation are almost universally present.
• 2.2. Presynaptic modulation of afferent input acts in many ways which tailor the inflow of sensory information to the behaviour of the animal, effectively providing a means of turning this on and off, or of combining information of the same or different modalities to refine responsiveness or clarify ambiguity.
• 3.3. Presynaptic modulation may act in several different roles on the same afferent.
• 4.4. A comparison of the mechanisms of presynaptic inhibition in different animals demonstrates the likelihood of a variety of common mechanisms,several of which may act simultaneously on the same terminal.These include changes in the conductance of the afferent membrane to Cl^-, K⁺and Ca²⁺ions, in addition to less well understood mechanisms that directly affect transmitter release.
• 5.5.A single transmitter can produce several effects on a terminal through the same or different receptors.
• 6.6. Ultrastructural studies of afferent terminals reveal that only a proportion of boutons on a given afferent may receive presynaptic input and that this may depend on the region of the nervous system in which these are found or on the identity of the postsynaptic neurons contacted.
• 7.7. The synaptic relationships of afferent terminals can be complex. In invertebrates different types of presynaptic neuron may interact synaptically,as may postsynaptic dendrites in vertebrates.
• 8.8. Axons presynaptic to afferent terminals in vertebrates frequently synapse also with dendrites postsynaptic to the afferents.
• 9.9. In both invertebrates and vertebrates reciprocal interactions between afferents and postsynaptic neurons are seen.
• 10.10. Ultrastructural immunocytochemistry reveals the likely dominance of GABA as an agent of presynaptic inhibition but also demonstrates the possible presence of other transmitters some of whose roles are less completely understood.

     

Evidence that protein kinase C is involved in regulating glucose transport in the adipocyte

• 1.1. The role of protein kinase C in the mechanism of stimulation of glucose transport in rat adipocytes was investigated.
• 2.2. Glucose transprt was stimulated by dioleoylglycerol (DOG), tetradecanoyl phorbol acetate (TPA) and phospholipase C (PLC).
• 3.3. Agents that inhibit protein kinase C (polymyxin B, gossypol and quercitin) also inhibited glucose transport that had been stimulated by DOG, TPA, PLC and insulin.

     

Subcellular distribution of metals within the kidney of the bivalve Mercenaria mercenaria (L.)

• 1.1. The subcellular distribution of nine transition metals (plus four additional elements) was measured in the kidney tissue of the quahog, Mercenaria mercenaria.
• 2.2. Elemental analyses of the subcellular fractions indicated three main patterns of metal distribution within kidney cells.
• 3.3. Barium, iron, manganese and lead were associated primarily with kidney granules.
• 4.4. Cadmium, copper, potassium and magnesium were found mainly in the cytosolic fraction.
• 5.5. Calcium, phosphorus and zinc were found in all isolated fractions, probably reflecting the important roles that these elements play in bivalve metabolism.
• 6.6. The organelle composition of the isolated subcellular fractions was determined using marker enzyme assays and microscopic techniques.

     

Ependymins and their potential role in neuroplasticity and regeneration: Calcium-binding meningeal glycoproteins of the cerebrospinal fluid and extracellular matrix

• 1.1. Ependymins are unique, highly divergent secretory proteins of the fish endomeninx. Thus far, no homologous sequences have been characterized in mammals.
• 2.2. Soluble ependymins are the predominant constituents of the cerebrospinal fluid of many teleost fish. A bound form of these glycoproteins is associated with the extracellular matrix probably with collagen fibrils. The latter may be the functional form of ependymins.
• 3.3. Ependymins bind Ca²⁺ via N-linked sialic acid residues leading to a conformational transition.
• 4.4. The molecular function of ependymins seems to be related to cell contact phenomena involving the extracellular matrix. For example, adhesive or anti-adhesive interactions may possibly influence ingrowing axons.

     

Ionic dependence and vanadate sensitivity of (Na+, K+)-ATPase isolated from branchial sac of ascidians

• 1.1. Ion dependence and vanadium-induced inhibition on branchial sac ATPase in five species of ascidian Phlebobranchiata (vanadium-accumulating) and Stolidobranchiata (iron-accumulating) were studied.
• 2.2. The ATPase was obtained from the microsomal fraction, which was prepared from each ascidian branchial sac.
• 3.3. The ATPase was dependent on Mg²⁺ and activated by exogenous Na⁺ + K⁺.
• 4.4. Ouabain inhibited the ATPase activity in vitro, 10 μM to 100 μM vanadate, in vitro, suppressed the (Na⁺, K⁺)-ATPase.

     

Changes in the activity of the adrenal cortex in fasted echidnas (Tachyglossus aculeatus) exposed to low ambient temperatures

• 1.1. The adrenal cortex is necessary for survival of echidnas at low ambient temperatures. In this study, adrenal gland activity was investigated in echidnas exposed to 2 days of cold (14°C) and fasting, alternating with 2 days at room temperature and feeding ad lib.
• 2.2. In the cold. 2.75 ± 0.29% (SD) of the initial body weight was lost daily. Plasma amino acid concentration did not change while glucose concentration decreased from 2.6 ± 0.3 to 1.5 ± 0.3 mmol/l with consecutive sessions of cold.
• 3.Plasma concentrations of corticosterone (7.2 ± 1.4 nmol/l) and cortisol (4.4 ± 1.9 nmol/l) were unchanged by repeated cold exposure. However, the adrenal response to ACTH stimulation decreased and the clearance of corticosteroids increased after cold exposure.
• 4.It was concluded that exposure to cold increases the utilization of glucocorticoids and decreases the capacity for their biosynthesis.

     

Proteomics Analysis of Extracellular Matrix Remodeling During Zebrafish Heart Regeneration

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Highlights

• •We have developed a decellularization protocol for ECM protein enrichment.
• •We have characterized the proteome of adult zebrafish heart ECM.
• •We describe dynamic changes in heart ECM proteome during regeneration.
• •We describe changes in heart ECM stiffness during regeneration.