Characterization of the glycine-dependent redox-cycling activity in animal fluids and tissues using specific inhibitors and activators: evidence for presence of PQQ

Pyrroloquinoline quinone, a redox cofactor first isolated from bacteria, efficiently catalyzes the nonenzymatic oxidation of glycine in the presence of nitroblue tetrazolium. We report that certain metallic cations and heterocyclic aromatic cations, like the N-methyl phenazonium cation and aryl-iodonium compounds, strongly and specifically inhibit this redoxcycling activity. The inhibition by metal cations is reversed by Tiron and that of the aromatic cations by Tiron and thyroxine. These inhibitors and activators affect authentic PQQ and the redox-activity of putative PQQ isolated from biological sources in a similar manner. This indicates that pyrroloquinoline quinone occurs naturally in animal tissues and fluids.

[Richter's hernia. An unusual disease course and incidence in a personal patient sample]

Richter's hernia is a special type of incarcerated hernia with strangulation of only a part of the circumference of the bowel wall. Diagnosis may be delayed for the frequent absence of intestinal obstruction or the mild local signs especially in the femoral site. Untreated, there may be formation of an abscess without communication to the peritoneal cavity with secondary formation of an enterocutaneous fistula. We describe the history of a 87 years old patient with a femoral hernia and formation of an enterocutaneous fistula 9 months after incarceration. Discussion with review of the literature.

[Non-familial ulcero-mutilating acro-osteopathy of the foot (Bureau-Barrière syndrome)]

We report on a case of severe acro-osteopathia ulcero-mutilans complicated by lethal endocarditis. The clinical course is presented with emphasis on the typical signs and symptoms. Diagnosis and treatment require a multidisciplinary approach to such patients.

Keratosis extremitatum (Greither's disease): clinical features, histology, ultrastructure

Keratosis palmoplantaris progrediens et transgrediens (Greither's disease) was first described by Greither in 1952. The inheritance pattern is autosomal dominant with variable expression. The clinical manifestation is characterized by diffuse palmoplantar keratoderma associated with hyperhidrosis and progressive extension of keratoderma to the dorsum of the hands and feet. In addition, hyperkeratotic plaques may occur on the elbows and knees. We describe a 44-year-old patient with typical features of Greither's disease. Immunohistologic and ultrastructural investigations are presented.

Is the antioxidant, anti-inflammatory putative new vitamin, PQQ, involved with nitric oxide in bone metabolism?

Our laboratory recently isolated free PQQ (2,7,9-tricarboxy-pyrroloquinoline quinone, methoxatin), a bacterial redox cofactor, from red cells, neutrophils, serum and milk and found free PQQ in CSF, synovial fluid and bile. The metabolism and functions of PQQ and ascorbate may be coupled. Physiologically, free PQQ catalyzes dioxygen-superoxide interconversion, and participates in both superoxide generation (respiratory burst) and scavenging (cell protection). Using a labeled aromatic o-diamine, superoxide formation by activated neutrophils was inhibited and the labeled phenazine adduct of PQQ could be isolated from the inhibited cells (Karnovsky et al., 1992). PQQ may convert xanthine oxidase to xanthine dehydrogenase (XD) and could be the physiological coenzyme of XD. PQQ plus copper, form a potent amine-oxidizing system. Shah et al., 1992 found that PQQ-Cu2+ catalyzes the oxidation of epsilon-amino groups in collagen and elastin. Rucker's lab (Smidt et al., 1991) has found that PQQ may be a vitamin for mouse pups. Watanabe et al., 1988 and Nishigori et al., 1989, showed that injected PQQ protects animals against oxidative stress injury. PQQ's in vivo antioxidant action, spares reduced glutathione. PQQ, as an actively transported organic anion, concentrates in cells. In other experiments (Aizenman et al., 1992), PQQ protected neurons against the neurotoxin action of the glutamate-receptor against NMDA. We shall consider possible roles for PQQ in the biosynthesis of nitric oxide (NO, endothelium-derived relaxing factor, EDRF) from L-arginine and in NO removal by superoxide. NO has now been linked to the inhibition of osteoclastic bone resorption.

[Transarticular amputation at the knee in peripheral arterial occlusive disease. Very positive experiences after routine use of the Klaes and Eigler technique]

In a retrospective study we compare our experience with the through-knee amputation in peripheral vascular disease. In the first 15 patients we used an amputation technique with circular incision. In about 50% of these patients we observed a delayed wound healing or they needed a reamputation to a higher bony level. In the 17 following patients we used the amputation technique described by Klaes and Eigler, using a posterior myocutaneous flap to cover the condyles. Only one of these patients needed a reamputation and another had a secondary wound healing. We conclude that the technique of through-knee amputation described by Klaes and Eigler is better adapted for patients with peripheral vascular disease.

Specific detection of quinoproteins by redox-cycling staining

Quinones and related quinonoid substances catalyze redox cycling at an alkaline pH in the presence of excess glycine as reductant. With nitroblue tetrazolium and oxygen present there is concomitant reduction of the tetrazolium to formazan. This property of quinonoid compounds is used for the specific staining of quinoproteins, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotted onto nitrocellulose. The dopa-containing vitelline proteins and the 6-hydroxydopa-containing bovine serum amine oxidase are stained with the nitroblue tetrazolium/glycinate reagent. Also, the mammalian quinoproteins, diamine oxidase and lysyl oxidase, purported to contain pyrroloquinoline quinone, tested positive in this procedure. No quinonoid components were detected in three putative pyrroloquinoline quinone-containing quinoproteins, dopamine beta-hydroxylase, lipoxygenase, and peptidylglycine-amidating monoxygenase. Redox-cycling staining therefore confirms the presence of covalently bound quinones in the copper-dependent amine oxidases, but not in two putative quinoprotein oxygenases. Clarification of the biological significance of quinolation should be facilitated by identification of quinoproteins using this approach.

Eczematous infiltrated plaques to subcutaneous heparin: a type IV allergic reaction

Two patients are described who had delayed reactions with eczematous plaques to subcutaneous injections of heparin. Subcutaneous challenge with high and low molecular weight heparin compounds were positive in both patients. Patch and intradermal tests with heparin were positive in one subject. Histological and immunohistochemical studies indicated that it was a type IV allergic reaction.

Acid-promoted tautomeric lactonization and oxidation-reduction of pyrroloquinoline quinone (PQQ)

Acid-treatment facilitates PQQ detection by electron ionization mass spectroscopy with a molecular ion at M/e 330 and a base ion formed by triple decarboxylation at M/e 198. Other ions found probably arise through acid-catalyzed tautomeric lactonization of PQQ to PQQ-lactone (PQQL) with subsequent oxidation of PQQL and reduction of PQQ. We propose that a carboxyl group, presumably the 9-carboxyl, attacks a double bond in PQQ, reversibly converting the 4,5-orthoquinone into an 4,5-enediol and forming an isomeric lactone, PQQL, of 330 daltons. The masking of carbonyls may explain the low reactivity of PQQ with carbonyl reagents in acid. Acid-promoted tautomeric lactonization with carbonyl-masking is known to occur with fluoresceins, phenolphthalein and other compounds, but has not been recognized before with PQQ. Acid-treated PQQ demonstrates molecular and other ions derived from reduced PQQ (PQQ(2H] or its lactone at M/e 332 with a base ion at M/e 200. There is compelling evidence for a dehydrogenated lactone, PQQ(-2H)L), at M/e 328 with a base ion at M/e 196. We suggest that PQQ, in tautomeric equilibrium with PQQL, oxidizes PQQL to PQQ(-2H)L (328 daltons), with its concurrent reduction to PQQ(2H) (332 daltons). With acidified D2O, PQQ shows deuterated products with ions at M/e values consistent with lactonization and oxidation-reduction. An analytically useful quinoxaline adduct, formed from PQQ and 2,3-diaminonaphthalene (PQQ-DAN) of 452 daltons, also undergoes acid-tautomerization-lactonization and oxidation-reduction similar to PQQ showing molecular ions at M/e 450, 452 and 454 and decarboxylation-derived strong (base) ions at M/e 318, 320 and 322.(ABSTRACT TRUNCATED AT 250 WORDS)

[Fornix rupture. A contribution to differential acute abdomen diagnosis]

The diffuse retroperitoneal extravasation of urine most often secondary to an ureteric calculus may present as a surgical emergency with localized or general abdominal symptoms. As the clinical signs are intriguing, history and a blurred psoas shadow on the plain film of the abdomen are the best guides to the right diagnosis definitely confirmed by an intravenous urography. Management usually is conservative and the recovery most often uneventful.

PQQ, the elusive coenzyme

The recently discovered redox coenzyme, PQQ (methoxatin), is widely distributed. Quantitation of protein-bound PQQ has been difficult, but unique redox cycling reactions, which reflect its striking biological properties, reveal trace amounts. PQQ is a potential target for drugs.

Methoxatin (PQQ), coenzyme for copper-dependent amine and mixed-function oxidation in mammalian tissues

The newly discovered coenzyme PQQ can now be measured at picomole levels with redox cycling methods developed in our laboratory. PQQ-peptides have been obtained from digests of the copper quinoenzymes, diamine oxidase, lysyl oxidase and dopamine-beta-hydroxylase. PQQ is present in egg yolk and milk, suggesting its immediate availability for developing embryos and newborn animals. We suggest that PQQ, when exposed in traumatized, ischemic, inflammed or pathological tissues, may catalyze the formation of large amounts of superoxide and should be considered as a source of oxidative stress when planning pharmacotherapeutic intervention. PQQ and quinoproteins play a role in the redox metabolism and structural integrity of cells and tissues.