Isolation and characterization of a hypervariable region [D4S163] on chromosome 4

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Demonstration of peptide-specific and cross-reactive epitopes in proteins reacting with antimitochondrial antibodies of primary biliary cirrhosis

Recently the main targets of antimitochondrial antibodies (AMA) of primary biliary cirrhosis have been identified as parts of three related mitochondrial multienzyme complexes, namely pyruvate dehydrogenase (PDH), branched chain alpha-ketoacid dehydrogenase (BKDH) and alpha-ketoglutarate dehydrogenase (alpha-KGDH). Usually AMA-positive PBC serum samples show reactivity to more than one of these, raising the question whether they are exclusively different antibodies or are, at least in part, the result of cross-reactive specificities. With Western immunoblotting, four antigens with molecular masses of 74, 52, 51 and 43 kDa, are recognized by PBC sera. In this study, using affinity purified antibodies from mitochondrial proteins immobilized on nitrocellulose blots, we demonstrate the presence of peptide-specific and cross-reactive epitopes in some targets. In particular, at least three different epitopes present in the 74-kDa protein (presumed to by PDH-E2) are also present in the 51-kDa protein (probably PDH-X), and two in the 52-kDa peptide (possibly BCKDH-E2). Moreover, the 43-kDa mitochondrial protein (the identity of which is more problematic) has three epitopes. One of these is also present in the 74-, 52- and 51-kDa proteins, a second in the 74- and 51-kDa, and a third seems to be peptide-specific. These results show that different sera with the same immunoblotting pattern of reactivity can have antibodies with different antigenic specificities and, conversely, that the same specificity can be responsible for more than one band.

The susceptibility of elastin-fatty acid complexes to elastolytic enzymes

Elastin in vivo is likely to be complexed with amphipathic ligands such as lipids. The susceptibility of stable [3H] elastin-fatty acid complexes to the action of porcine pancreatic elastase (PPE) and to human neutrophil lysates over time was assessed. Elastolysis by PPE of substrates prepared with oleic or linoleic acids was initially higher (for up to 2 hours) than that of uncomplexed elastin. Stearic acid and elaidic acid (the trans isomer of oleic acid) did not enhance the elastolytic rate above control. The stimulatory effect of oleic and linoleic acids appeared to derive from increased adsorption of PPE onto elastin; the loss of stimulatory activity over time occurred in parallel with a progressive decrease in adsorption. All fatty acids tested inhibited elastolysis by neutrophil lysates, the effect being particularly marked with oleic and elaidic acids. These results indicate that 1). Complexed fatty acids can modulate the rate of elastin breakdown by elastases; 2). The effects observed with PPE are due to differences in adsorption of enzyme onto substrate, possibly as a result of steric considerations; 3). Since elastolysis by neutrophil lysates is inhibited by all fatty acids, the properties of different elastolytic enzymes should be considered in in vitro model systems of connective tissue breakdown.

Two cases of fulminant Mycoplasma pneumoniae pneumonia within 4 months

We report the clinical course and diagnostic findings in two patients with life-threatening Mycoplasma pneumoniae (MP) pneumonia who were treated in the same hospital in the course of only 4 months. The patients were previously healthy adults, aged 31 and 37 years, respectively. In both of them severe complications occurred which coincided with the acute MP respiratory infection.

The mechanism of the halothane-dependent efflux of calcium from rat-liver mitochondria

The halothane-dependent, calcium-induced loss of respiratory control in rat liver mitochondria [1, 2] is Mg2plus -dependent and is accompanied by an enhanced mitochondrial swelling. It is suggested that this swelling reflects an increase in calcium activity in the matrix space, due to a decrease in binding of the accumulated cation. This change in the partition of intramitochondrial calcium is correlated with an inhibition by halothane of energy-independent, calcium-induced swelling. The enhanced swelling associated with the active accumulation of calcium in the presence of halothane does not lead to a marked increase in permeability to other ions. Nevertheless, under conditions of energised calcium uptake, and in the presence of Mg2plus, a halothane-dependent, ruthenium red-insensitive efflux of calcium is observed. This is consistent with the proposed halothane-dependent increase in the matrix activity of accumulated Ca2plus. It is suggested that this mechanism accounts for the previously postulated [2] futile cycle of calcium uptake and release induced by halothane in rat liver mitochondria.

[Contaminating substances in 22 over-the-counter fish oil and cod liver oil preparations: cholesterol, heavy metals and vitamin A]

Fish oil capsules are increasingly used by self-medicating patients. We studied 22 commercial fish oil and menhaden oil preparations in respect to accompanying substances that could be harmful. The substances measured were: cholesterol as determined by gas liquid chromatography, heavy metals measured by atomic absorption, and vitamin A as determined by high-performance liquid chromatography (HPLC). The contents of cholesterol and heavy metals were in ranges which can be regarded as negligible; the content of vitamin A in menhaden oils, however, was found in amounts which warrant that pregnant women do not exceed the dosage as recommended by the manufacturers.

Expression of the primary biliary cirrhosis antigens in yeast: aspects of mitochondrial control

The mitochondria of 21 yeast strains were tested for the expression of primary biliary cirrhosis (PBC) specific antigens. The amounts of the antigens in the mitochondrial preparations varied with the strains. Genetic analysis of the strain differences in antigen expression indicated nuclear control which was complex. Those strains expressing the least amounts of antigens exhibited coagulating mitochondria in organellar preparations. Additional evidence relating expression of antigens to the physiological/structural state of mitochondria was that cells grown in the presence of the mitochondrial uncoupling agent, 2,4-dinitrophenol (DNP), failed to produce any antigens, and that glucose repression of mitochondria suppressed antigen expression. Blockage of mitochondrial protein synthesis either through petite mutation or by culture in the presence of erythromycin decreased the content of antigens in the mitochondria but did not completely block antigen production. The presence of the PBC antigen in the mitochondria of these cells with nonfunctional mitochondrial synthesizing machinery further indicates that these antigens are cytoplasmically synthesized. Analysis of the pre- and postmitochondrial fractions of all homogenates confirmed that the antigens are not only cytoplasmically synthesized but also have an extramitochondrial location in cells, probably in the plasma membrane.

Studies on the nature of adenosine diphosphatase activity from rat liver mitochondria

Adenosine diphosphatase (ADPase) activity was studied in rat liver with [beta-32P]ADP as a substrate. Mitochondria and outer mitochondrial membrane fractions were isolated and assayed for ADPase and various marker enzymes. ADPase activity was strikingly reduced when the outer membranes were removed from the mitochondria whether by digitonin treatment or osmotic shock. Addition of the inter-membrane space subfraction to the purified outer membranes resulted in enhanced ADPase activity. Addition of the inter-mitochondrial membrane enzyme adenylate kinase to outer membranes also produced a large stimulation of activity. The ADPase activity could also be reconstituted in vitro with adenylate kinase and either mitoplast ATPase or ouabain-sensitive (Na+ + K+ + Mg2+)-ATPase. Chloroform-released ATPase, however, was not capable of producing an ADPase activity when combined with adenylate kinase. Gel permeation chromatography of Triton-solubilised outer mitochondrial membranes was unable to resolve ADPase activity from contaminating ATPase. These results suggest that the majority of ADPase activity in rat liver mitochondria consists of the coupled activity of adenylate kinase and ATPase.

Discovery of a novel multilocus DNA polymorphism [DNF24]

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Comparison of effects of inhibitors on adenosine triphosphatase and adenosine diphosphatase activities in rat-liver mitochondria

Adenosine diphosphatase (ADPase) activity and ATPase activity were assayed in rat liver mitochondria and outer mitochondrial membrane preparations with [beta-32P]ADP and [gamma-32P]ATP as substrates. Inhibition studies were performed with the mitochondrial ATPase inhibitor oligomycin and the adenine nucleotide transport inhibitor, carboxyatractyloside. Kinetic studies were also performed with the nucleotide thiophosphate analogs adenosine 5'-O-thiophosphate, adenosine 5'-O-(2-thiodiphosphate) and adenosine 5'-O-(3-thiotriphosphate) which can act as inhibitors of phosphohydrolases. It is concluded that part of the apparent ADPase activity of intact mitochondria is mediated via ATPase, presumably in conjunction with adenylate kinase. In addition the outer mitochondrial membrane appears to show a distinct ADPase not attributable to contamination by inner membrane ATPase.

Differential growth inhibition of human diploid fibroblasts by 2-deoxyglucose and antimycin A with ageing in vitro

The relative growth inhibitory effects of 2-deoxyglucose and antimycin A were monitored at five stages during the life-span in vitro of human diploid fibroblasts. A marked age-dependent response was observed with 2-deoxyglucose but not with antimycin A. The results confirm an increase in the rate of glycolysis with ageing, which appears to be independent of cellular mitochondrial respiratory chain capacity. This may be associated with reduced utilization of the hexose monophosphate shunt and a consequent decline in the availability of ribose moieties for nucleic acid biosynthesis.

Discrimination between M2 and M4 antimitochondrial antibodies in primary biliary cirrhosis

10 sera were studied from patients with primary biliary cirrhosis (PBC), that were anomalous in their reactivity against mitochondrial antigens as detected by Western blotting. They had low reactivity against the major, M2 reactive antigen (Mr for beef heart mitochondria, 74 Kd) but reacted against an antigen of Mr 52 Kd (species independent) which was apparently inaccessible in submitochondrial particles (SMP) on ELISA and which was not present in chloroform-released ATPase preparations. In all respects this differed from the characteristics of the M2 antigens and it is concluded that these sera are detecting predominantly the M4-reactive antigen.

Mitochondrial antigenic structure and enzyme activity in ageing human diploid fibroblasts

It has been proposed that cellular ageing may be caused by loss of mitochondrial function due to the action of free radicals. To investigate this hypothesis, antigenic structures of the mitochondrial inner membrane/matrix and of the outer mitochondrial membrane of human diploid fibroblasts were monitored by immunoblotting at four stages during cellular lifespan in vitro. At the same time, specific activities of the enzymes oligomycin-sensitive ATPase (O-S ATPase), malate dehydrogenase (MDH) and glutamate dehydrogenase (GDH) were assayed to assess the functional capacity of cellular oxidative phosphorylation and of the tricarboxylic acid cycle. No changes were found with ageing in inner mitochondrial membrane-associated matrix components, or in the activities of O-S ATPase and MDH. However GDH activity increased significantly with ageing in vitro, possibly indicating greater amino acid utilization for energy production in older cells. There was loss of an outer mitochondrial membrane antigen, of approximate molecular weight 60 kilodaltons (kDa), in the oldest cells tested, which may influence outer membrane transport capacity late in the cellular lifespan. Overall, the results fail to provide support for the hypothesis that ageing primarily results from free radical-induced impairment of mitochondrial function.

Correlation of oligomycin-sensitive ATPase activity in trypanosomes with their content of an antigen to primary biliary cirrhosis

The amounts of an antigen to primary biliary cirrhosis (PBC) which occur in subcellular fractions of Trypanosoma rhodesiense and T. lewisi correlate positively with the oligomycin-sensitive (OS) ATPase activity of these fractions. This result is consistent with the mitochondrial ATPase association of the antigen in mammalian and other cells. Higher levels of OS-ATPase and of PBC antigen in T. lewisi accord with a more extensive mitochondrial development in this species.