Dystrophin in electric organ of Torpedo californica homologous to that in human muscle

We have found that dystrophin is highly concentrated at neuromuscular junctions and innervated membranes of the electric organ of Torpedo californica. In acetylcholine receptor-rich Torpedo membrane preparations dystrophin represents approximately 0.4% of total protein and can be extracted from these membranes by alkaline treatment in the absence of detergent, indicating that it is a peripheral membrane protein. Polyclonal antibodies raised against electrophoretically isolated Torpedo dystrophin cross-react with dystrophin in human muscle and unequivocally discriminate between normal and Duchenne muscular dystrophy patient's muscle. These results indicate that dystrophin is phylogenetically a highly conserved protein and that the relatively abundant dystrophin in electric organ would facilitate further investigations of its structure and function.

Purification and characterization of extracellular phospholipase A2 from human synovial fluid in rheumatoid arthritis

Extracellular phospholipase A2 was purified about 1.7 X 10(5) fold to near homogeneity from human synovial fluid of rheumatoid arthritis by sequential use of column chromatographies on heparin-Sepharose, butyl-Toyopearl, and reversed-phase HPLC. The final preparation showed a single band on SDS-polyacrylamide gel electrophoresis, and its molecular mass was estimated to be approximately 13,700 daltons. The purified enzyme had a pH optimum of 9.0 and required Ca2+ for maximum activity. It hydrolyzed phosphatidyl-ethanolamine more effectively than phosphatidylserine and phosphatidylcholine. These properties were similar to those of an extracellular phospholipase A2 detected in the peritoneal cavity of caseinate-treated rats.

Characteristics and pathophysiological roles of extracellular phospholipase A2 in inflamed sites

Extracellular phospholipase A2 found in inflamed sites of human and rat was purified and characterized. Phospholipase A2 isolated from peritoneal exudates of rat treated with casein, that isolated from human synovial fluids in rheumatoid arthritis, that secreted from activated platelets of rat and rabbit share common structural and biochemical features. Possible roles, dynamics and regulation of these extracellular phospholipases in inflammatory processes will be discussed.

Normal and dystrophin-deficient muscle fibers in carriers of the gene for Duchenne muscular dystrophy

Dystrophin is the gene product that is affected in Duchenne muscular dystrophy (DMD). Antibodies against dystrophin were used to study the protein in muscle fibers of carriers of the gene. The results showed that DMD carriers have normal and dystrophin-deficient fibers. Dystrophin immunohistochemistry may be helpful for the detection of DMD carriers.

Hydrolysis of platelet activating factor and its methylated analogs by acetylhydrolases

We examined the substrate specificity of PAF-degrading enzymes from various sources using platelet activating factor (PAF) and its synthetic analogs. The results were as follows: 1) Tissue-originated acetylhydrolases, such as rat kidney soluble enzyme, deacetylated 1S-methyl-1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (1S-Me-PAF) slightly more rapidly than PAF, whereas plasma acetylhydrolase hydrolyzed PAF more effectively than 1S-Me-PAF. 2) Rat polymorphonuclear leukocytes, monocytes, and lymphocytes homogenates showed an appreciable acetylhydrolase activity, the substrate specificity of which resembled that of the plasma enzyme. 3) Pleural exudates in an experimental pleurisy induced in rats by carrageenan contained an acetylhydrolase activity, the properties of which were similar to those of the plasma enzyme. 4) An extracellular phospholipase A2 activity, which was also observed in the pleural exudate and required Ca2+ ion for maximum activity, seemed not to participate in the deacetylation of PAF, since addition of EDTA did not affect the PAF deacetylation catalyzed by the pleural exudate. These findings indicate that the inactivation reaction of PAF present in the extracellular space is mainly catalyzed by plasma acetylhydrolase, which yields lysoPAF.

Stereoselective effects of lysophosphatidylserine in rodents

1. The pharmacological action of the L- and D-enantiomers of lysophosphatidylserine has been studied in vivo by following the increase in blood and brain glucose content caused by this phospholipid in mice. Preliminary experiments have confirmed that these effects are the consequence of lysophosphatidylserine-induced mast cell activation since they are not observed in mast cell-deficient mice bearing the W/Wv genotype. 2. Maximal hyperglycaemic response and brain glucose accumulation occur at 10 mg kg-1 lysophosphatidyl-L-serine (i.v.). Half-maximal effect is at 3.5 mg kg-1. Lysophosphatidyl-D-serine at doses of up to 25 mg kg-1 i.v. elicits 40% (blood glucose) and 60% (brain glucose) of the maximal effect. The difference in activity between the two enantiomers is also observed in the desensitization to lysophosphatidylserine occurring when this phospholipid is administered by the oral route. 3. Lysophosphatidyl-L-serine is more active than the D-enantiomer in mouse isolated peritoneal mast cells. Activity ratios of 10 are observed between 20 and 50% histamine release. Similar results are obtained with rat isolated peritoneal mast cells. 4. It is concluded that the configuration of the alpha carbon atom of serine influences the activity of lysophosphatidylserine in vivo and in vitro. Thus, the appropriate position of the serine amino group is required for optimal interaction of the phospholipid head group and a receptor in the mast cell membrane.

Antitumor activity of synthetic alkylphospholipids with or without PAF activity

1-O-Octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET-18-OMe) has been reported to possess definite antitumor activity in vivo. Twenty-two alkyl lysophospholipid analogs were chemically synthesized, and their antitumor activity against mouse experimental tumors (Sarcoma 180, MM46, P388) was examined. Among them, 1-O-octadecyl-2-O-acetoacetyl-rac-glycero-3-phosphocholine was found to show antitumor activity similar to ET-18-OMe with less acute toxicity. Intravenous injection of the ET-18-OMe with sn-3 configuration retarded the subcutaneous growth of Sarcoma 180 cells effectively, while the growth inhibition by the sn-1 isomer was much less effective. This stereospecificity was similar to that observed in their activities as platelet-activating factor (PAF) agonists. The acetoacetyl compound, another PAF agonist, showed similar stereospecific antitumor action in vivo. These findings suggest that some alkyl lysophospholipids may activate host cells to a cytostatic stage against tumor cells in vivo through binding to a PAF receptor. Our preliminary results indicated that the responsible cells under these conditions might be primarily immature macrophages present in the bone marrow. No appreciable or even adverse stereospecificity was observed in the different sets of experiments where the activity of ET-18-OMe against MM46 tumor cells in vivo or the direct cytotoxicity against human promyelocytic leukemia HL-60 cells in vitro was examined. Under some conditions, the antitumor activity of ET-18-OMe in vivo may be revealed through direct cytotoxicity and/or modulation of the host defense system by "nonspecific" mechanisms. Some alkylphospholipids without PAF activity may also show antitumor activity through similar "nonspecific" mechanisms.

Purification and characterization of extracellular phospholipase A2 from peritoneal cavity of caseinate-treated rat

Peritoneal exudate produced in rat injected with caseinate contained extracellular phospholipase A2. The activity required Ca2+ ion and had a pH optimum of 9 (Chang, H.W., Kudo, I., Hara, S., Karasawa, K., & Inoue, K. (1986) J. Biochem. 100, 1099-1101). This phospholipase A2 was purified about 14,000-fold to near homogeneity by the sequential use of column chromatography on Sephadex G-75, Toyopearl HW-65, and TSK ODS-120T reverse-phase HPLC. The final preparation showed a single protein band on SDS-polyacrylamide gel electrophoresis, and its molecular weight was estimated to be approximately 13,500. The enzyme hydrolyzed phosphatidylethanolamine (PE) and phosphatidylserine (PS) more effectively than phosphatidylcholine (PC). When 1-acyl-2-[1-14C]inoleoyl-sn-glycero-3-phospholipids were used as a substrate, the apparent Km values were 0.027 mM with PE, 0.032 mM with PS, and 0.1 mM with PC, and the Vmax values were 105 mumol/min/mg with PE, 71 mumol/min/mg with PC. The enzyme activity was inhibited by p-bromophenacyl bromide, dithiothreitol, and mepacrine. The amino acid sequence of the NH2-terminal portion and the amino acid composition of the purified enzyme were determined. They were different from those of rat pancreatic phospholipase A2, but very similar to those of phospholipase A2 secreted from rat platelets.

Extracellular phospholipase A2 activity in peritoneal cavity of casein-treated rats

An extracellular phospholipase A2 was detected in the peritoneal cavity of rats injected intraperitoneally with casein. This activity required Ca2+ ion and had a pH optimum of 9. The increase of phospholipase A2 activity in the peritoneal fluid as a function of time roughly paralleled the increase in the number of polymorphonuclear (PMN) leukocytes found in the peritoneal cavity. Phospholipase A2 activity was also observed in rat PMN homogenates, and its characteristics were similar to those of the enzyme found in cell-free peritoneal fluid fraction. PMN leukocytes may release non-lysozomal phospholipase A2 into the extracellular space as 'inflammation reactions' proceed.

Abundance of dimethylamine in seafoods: possible implications in the incidence of human cancer

Levels of secondary and primary amines in various squids and other seafoods were determined by the newly developed dabsylation-HPLC method. Ammonia and dimethylamine were found in all of the seafoods analyzed, and some of them also contained methylamine, isobutylamine, ethylamine, and/or diethylamine. Extremely high levels of dimethylamine and methylamine were detected in all squids analyzed and in certain other seafoods. Very high activity of trimethylamine oxidase was observed in fresh squid tissue. Pyrolysis of sarcosine HCl and trimethylamine HCl yielded high levels of dimethylamine and methylamine. Various cooking conditions (extracting, frying, and broiling) had profound effects on amine content. Broiling was found to elevate the amine contents in most seafoods.

Long-lived metastable states and hysteresis in the binding of acetylcholine to Torpedo california acetylcholine receptor

Studies of the binding of [3H]acetylcholine to receptor-rich membranes of Torpedo californica electric organ under conditions that normally lead to a state of equilibrium did not give rise to equilibrium binding curves. Instead, the acetylcholine receptor was found to develop very long lived metastable states resulting in hysteresis in binding. Under conditions where the concentration of free [3H]acetylcholine is both less than 0.1 microM and smaller or comparable to the total receptor concentration, the degree of binding of acetylcholine depends on the rate, i.e., the mode, of increasing the acetylcholine concentration (rapid mixing vs. dialysis). The equilibrium positive cooperativity in high-affinity acetylcholine binding previously inferred from the data is deceiving; the curvature in Scatchard representations is a consequence of long-lived nonequilibrium distributions between high-affinity and lower affinity receptor conformers. By manipulation of the experimental conditions, true equilibrium binding, resulting in a linear Scatchard binding curve, was obtained and yielded the apparent equilibrium constant, K = 5 +/- 1 nM at 4 degrees C. The stoichiometry of the high-affinity site associated with this K value was found to be one acetylcholine per receptor monomer (Mr 250 000) when carefully standardized [3H]acetylcholine analyzed for both radiopurity and acetylcholine concentration was used. While our fresh membrane fragments prepared in the presence of 4 mM Ca2+ revealed up to twice as many 125I-alpha-bungarotoxin sites in 0.1% nonionic detergent relative to those assayed in the absence of detergent, nonionic detergent treatment of membrane fragments did not result in any change in total available acetylcholine binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphoglycerate kinase deficiency myopathy: Biochemical and immunological studies of the mutant enzyme

A new phosphoglycerate kinase variant (PGK New Jersey) has been purified from muscle and cultured fibroblasts of a patient with recurrent myoglobinuria. The mutant enzyme had higher than normal affinity for adenosine triphosphate (ATP) and 3-phosphoglycerate, and a shift of the pH optimum towards the acidic side. Antibodies raised against PGK purified from normal muscle were used to evaluate the presence of immunologically cross-reacting enzyme protein in tissues from the patient. Immunodiffusion and an antibody consumption test showed the presence of reduced amounts of cross-reacting material in the patient's muscle. Several PGK variants have been characterized in asymptomatic individuals or in patients with hemolytic anemia. The biochemical features of PGK New Jersey, the only known variant associated with recurrent myoglobinuria, distinguish this mutant enzyme from others.

Augmented anti-acetylcholine receptor response following long-term penicillamine administration

Because of the association of D-penicillamine (DP) therapy with myasthenia gravis, we have studied long-term DP treatment in five inbred strains of mice with doses comparable to those used in patients with rheumatoid arthritis. No clinical weakness or anti-acetylcholine receptor (AChR) antibody developed with up to 6 months of treatment, but augmented responses did occur to challenge with purified AChR in adjuvant. Anti-AChR antibody titers in C57BL/6 and C3H/He mice were significantly higher after challenge with AChR in DP-treated than in control mice. Augmented anti-AChR titers were not seen in strain A mice, but after 6 months of DP treatment increased susceptibility developed to the induction of experimental autoimmune myasthenia gravis. Nine weeks after challenge with purified AChR, 10 of 11 mice developed clinical weakness, leading to death in 6. Results of edrophonium testing were positive in 5 of 6 mice, and electrophysiological abnormalities were demonstrated in 3 of the surviving mice. Long-term DP treatment is associated with augmented anti-AChR antibody responses in C3H/He and C57BL/6 mice, and increased susceptibility to experimental autoimmune myasthenia gravis in strain A mice.

N-nitrosophenacetin: its synthesis, characterization, mutagenicity, and teratogenicity

Reaction of phenacetin (CAS: 62-44-2; p-acetophenetidide) with nitrous fumes (N2O3) in glacial acetic acid at 0-5 degrees C yields N-nitrosophenacetin (NP), 2-nitrophenacetin, N-nitroso-2-nitrophenacetin (NNP), and other compounds. Both NP and NNP are fairly stable at low temperature (-30 degrees C) but extremely labile at ambient temperature. NP (median lethal dose to Sprague-Dawley rat: 21 mg/kg body wt) is 80 times more toxic than its parent compound phenacetin and is directly mutagenic to bacterial cells including Salmonella typhimurium and Sarcina lutea. The mutagenicity of NP is comparable to that of N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7; 1-methyl-3-nitro-1-nitrosoguanidine] and requires no microsomal metabolic activation. The teratogenic potential of NP was studied in White Leghorn chick embryos given a single dose of 5-15 micrograms/egg on day 6 of incubation. A low incidence of exencephaly and eyelid defect and a high incidence of feather and claw malformations were found in the treated group; no such malformed embryos were found in the control group. The teratogenicity of NP was found to be weaker than that of MNNG, but stronger than that of N-methyl-N-nitrosourea (CAS: 684-93-5), dimethylnitrosamine (CAS: 62-75-9; N-nitrosodimethylamine), and diethylnitrosamine (CAS: 15-18-5; N-nitrosodiethylamine).

Alpha-bungarotoxin binding to the myotome and choline acetyltransferase activity in the rabbit embryo

We have previously found incomplete sarcomeres and acetylcholinesterase activity in the myoblasts of the myotome of the rabbit at day 13 of gestation. We now report that an acetylcholine (ACh)-synthesizing enzyme and the nicotinic receptor are present at this stage as well. A study of the myotome using [125I]alpha-bungarotoxin shows that the mononucleated myoblasts have alpha-bungarotoxin binding sites before they migrate away to form multinucleated myotubes. Choline acetylcholinesterase activity and/or a different ACh-synthesizing enzyme are found at early stages of development, even before the spinal nerve has formed. An ACh-synthesizing enzyme is present in the notochord, a neural tube-dorsal root ganglion preparation, as well as in rows of myotomes separated from the latter preparation. Assays of isolated myotomes with very little adherent mesenchyme indicate that the enzyme is located either within the myotome or in its immediate vicinity. Cholinergic components, therefore, are associated with the mononucleated myoblasts of the myotome before they fuse to form myotubes and before they receive their permanent innervation.

High concentrations of dimethylamine and methylamine in squid and octopus and their implications in tumour aetiology

The levels of the common secondary amines in various squid, in octopus and in 17 other seafoods were determined by HPLC. Ammonia and dimethylamine were found in all of the seafoods tested and some of them also contained methylamine and/or ethylamine. Particularly high levels of dimethylamine (946-2043 ppm) and methylamine (38-255 ppm) were detected in various species of squid and in the octopus. Reaction of nitrite in acidic medium with aqueous extract of squid yielded appreciable amounts of N-nitrosodimethylamine. The optimum pH for this reaction was around 2.4. Dimethylamine in dried squid tissues was readily extracted with water or 1% sodium carbonate solution. Heat treatment of dried squid at 200 degrees C was found to increase its amine content dramatically. It appeared that pyrolytic decarboxylation of some amino acids might cause this increase. Squid is a popular seafood in Japan and other oriental countries. The high incidence of stomach cancer in Japan and China is thought by epidemiologists to be associated with traditional Japanese and Chinese diets. Our present finding that squid and other seafoods contain unusually high levels of dimethylamine and other amines adds to the evidence that dietary factors may have an important role in the aetiology of stomach cancer and other gastro-intestinal tumours.

Penicillamine-induced myasthenia gravis: effects of penicillamine on acetylcholine receptor

Autoimmune diseases, including myasthenia gravis, occur in patients treated with D-penicillamine. Because D-penicillamine might induce autoantibodies by the mechanism of antigenic alteration, we studied the reaction of D-penicillamine with purified acetylcholine receptor from Torpedo californica. We found that brief exposure to D-penicillamine resulted in its covalent attachment to two receptor subunits, alpha (40,000 daltons) and gamma (59,000 daltons), presumably by reduction and formation of mixed disulfides. Furthermore, D-penicillamine treatment resulted in a dramatic modification of the equilibrium acetylcholine binding properties of both purified receptor and receptor-rich membrane fragments.

Factors in the production of experimental autoimmune myasthenia gravis in acetylcholine receptor immunized rabbits

The development of experimental autoimmune myasthenia gravis (EAMG) was studied in 10 rabbits which were repeatedly injected with Torpedo acetylcholine receptor (AChR). Serum samples were obtained at various times for determination of complement fixing antibody level, serum complement level and the capacity of serum to inhibit neuromuscular transmission in amphibian muscle (passive transfer inhibiting capacity, PTIC). In seven animals the rise in level of circulating antibody occurred immediately before or in synchrony with the development of EAMG and frequently at such times serum complement rose irregularly. The PTIC was elevated during appearance of EAMG. In some animals a rise in complement fixing antibody level occurred without appearance of EAMG; in two others EAMG appeared without significant rise in antibody level. The data indicate that development of EAMG is associated with the production of antibodies which are capable of depressing neuromuscular transmission by reducing the sensitivity of the postjunctional membranes to acetylcholine. This depression can be potentiated by serum complement. Some but not all of the antibodies produced appear to fix complement when combined with Torpedo AChR. Evidence indicating possible existence of a presynaptic contribution to the development of EAMG is given.

Thymic abnormalities: antigen or antibody? Response to thymectomy in myasthenia gravis

The therapeutic value of thymectomy for myasthenia is still questioned although it retains an important place among management modalities that strive for sustained remission. Questions derive from uncertainty as to appropriate timing, variable extent of resection and quantitation of response. Forty-seven patients, followed one to seven years, underwent an extended transsternal or combined transcervical-transsternal procedure with anterior mediastinal exenteration. Sixteen have been in complete remission from six months to six years, four are asymptomatic on occasional pyridostigmine and eight are significantly improved. Evaluation of thymic pathology (hyperplasic, involuted areas, and thymoma) included a search for thymic myoid cells by fluorescence cytochemistry. Antibodies to acetylcholine receptor present in 38 of 43, decreased post-operatively to normal in four, by 50% to 80% in 14, by 20 to 50% in three and were unchanged in 14. Most remissions occurred in young women with noninvoluted hyperplastic glands and variably high anti-AChR titers which dropped toward normal in seven of 15. These results encourage us to utilize this procedure routinely.

Spectrophotometric determination of reaction stoichiometry and equilibrium constants of metallochromic indicators. III. Antipyrylazo III complexing with Ca2+ and acetylcholine receptor protein

Stoichiometries, equilibrium constants and optical extinction coefficients of calcium-antipyrylazo III (An) complexing are determined with the analytical method described in article I of this series. Spectrophotometric Ca titrations of An at the wavelengths 595 and 710 nm indicate overall dissociation equilibrium constants for the complexes CaAn, CaAn2 and Ca2An to be 4.5 x 10(-4) M, 1.1 x 10(-8) M2 and 1.5 x 10(-6) M2, respectively, extrapolated to zero ionic strength. Ca titrations of solutions containing An plus acetylcholine receptor protein give clear evidence that An binds to the protein to a large extent in the presence of Ca2+; furthermore, addition of acetylcholine results in release of protein-bound Ca and An. This is the first reported indication that antipyrylazo III binds to biological material and questions the usefulness of this dye as a Ca indicator in biological systems.