Enhancement by tetraphenylboron of inhibition of mitochondrial respiration induced by 1-methyl-4-phenylpyridinium ion (MPP(+))

The effect of tetraphenylboron (TPB(?)), an activator of a membrane transport of lipophilic cations, on the inhibition of mouse liver mitochondrial respiration induced by a neurotoxin, 1-methyl-4-phenylpyridinium ion (MPP(+)), and by some structurally related compounds was studied. Of the compounds tested, MPP(+) and 4-phenylpyridine (4-PP) significantly inhibited the respiration in an ADP-activated oxidation of substrates (state 3). TPB(?), dose-dependently, shortened the lag time of MPP(+)-induced inhibition and thus lowered the concentrations of MPP(+) for the inhibition. However, TPB(?), even at the high concentration (10 ?M), did not significantly affect 4-PP-induced inhibition. Carbonyl-cyanide-m-chlorophenylhydrazone (CCCP) blocked the respiratory inhibition by MPP(+), independent of K(+) concentration in the medium, and valinomycin blocked the inhibition only in the medium containing high K(+) concentration. Determination of the intramitochondrial MPP(+) concentration revealed about 1000-fold concentrated MPP(+) from that in the medium during the incubation with TPB(?), indicative of potentiation of MPP(+) transport into mitochondria by TPB(?). This might account for the enhancement of respiratory inhibition by MPP(+). In the case of 4-PP, it will penetrate the mitochondrial membrane and intrinsically inhibit the respiration, but cannot accumulate in mitochondria. The present results indicate that, although the inhibitory potency of MPP(+)per se is similar to 4-PP, MPP(+) will be highly concentrated within mitochondria by the membrane potential, as the drive force for its transport.

Study of inhibition mechanisms of glycosaminoglycans on calcium oxalate monohydrate crystals by atomic force microscopy

Atomic force microscopy (AFM) was applied to the (-101) faces of calcium oxalate monohydrate (COM) crystals grown from calcium oxalate (CaOx) solutions. Microstructures of many spiral hillocks with step height of 1 nm were observed on the faces. Then using AFM in situ, we analysed the re-growth process of the spiral steps on the face of COM seed-crystals in CaOx growth solutions that contained growth inhibitors of glycosaminoglycans and studied their inhibition mechanisms on COM crystals. The total morphology of the faces of COM seed crystals re-grown in the CaOx growth solutions was assessed by scanning electron microscopy (SEM). In the growth solution without glycosaminoglycans (control experiment) or with chondroitin sulphate (ChS), AFM images and SEM micrographs of the faces of the re-grown seed crystals showed two-dimensional (2D) nucleation although 2D nucleation was delayed in the presence of ChS. However, the addition of dermatan sulphate (DS) to the growth solution resulted in isotropic growth by a step flow mode and spiral mechanism. With regard to the main inhibition mechanisms of two glycosaminoglycans (ChS and DS) on COM crystals, it can be concluded from these results that ChS delays 2D nucleation and DS inhibits 2D nucleation.

Uptake of 1-methyl-4-phenylpyridinium ion (MPP+) and ATP content in synaptosomes

Symptoms such as those in Parkinson's disease are known to be induced by the neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). We tried to quantitatively measure synaptosomal MPP+ uptake using an MPP+ selective electrode to study the correlation between MPP+ uptake and respiratory inhibition. Synaptosomal MPP+ uptake was low but could be increased by the addition of glucose as an energy substrate, or increased with an increase in the concentration of MPP+. The rate of uptake was 0.2 nmol/mg protein/min at 50 microM MPP+. Tetraphenylboron (TPB+), which enhances cation permeability, increased MPP+ uptake, and the increase was proportional to the TPB+ concentration. When external MPP+ concentration was increased above 200 microM, ATP was depleted and the uptake of MPP+ decreased, which resulted in the release of intrasynaptosomal MPP+. MPP+ uptake was also decreased by depolarization of the membrane potential in synaptosomes. MPP+ was presumed to be distributed across both the synaptosomal and inner mitochondrial membranes, and to be affected by membrane potential as a lipophilic cation. When respiration of the inner mitochondria was inhibited by increasing the intrasynaptosomal MPP+ concentration, the concentration of MPP+ in cytosol was presumed to increase by the release of MPP+ from the mitochondria, and synaptosomal MPP+ uptake would then be decreased.

Purification and characterization of a rhamnogalacturonase with protopectinase activity from Trametes sanguinea

In a culture filtrate of Trametes sanguinea IFO 6490, we found a protopectin-solubilizing enzyme, protopectinase-T, that did not degrade polygalacturonic acid. The enzyme was purified to homogeneity with hydrophobic, cation-exchange, anion-exchange, and size-exclusion chromatographies. It had an apparent molecular mass of 55 kDa by SDS/PAGE and 39 kDa by size-exclusion chromatography on Superose 12. The isoelectric point was at pH 8.1. Protopectinase-T was stable from pH 3.0 to 6.0 and at temperatures up to 50 degrees C. The optimum pH for enzyme activity was 4.0 at 37 degrees C, and the optimum temperature was 50 degrees C at pH 5.0. Protopectinase-T catalyzed the release of highly polymerized pectin from lemon peel protopectin.

Scanning electron microscopic study of the effect of citrate and pyrophosphate on calcium oxalate crystal morphology

The effects of citrate and pyrophosphate on the morphology of calcium oxalate monohydrate crystals formed in a supersaturated calcium oxalate solution were examined by scanning electron microscopy. Within the normal range of urinary concentrations, citrate and pyrophosphate affected the morphology of the crystals. The length/width ratio of the crystals decreased at higher concentrations of citrate and pyrophosphate. Citrate seems to have a dual mechanism of inhibition of crystal growth (binding to the crystal surfaces) and of complexation (with calcium in the solution). Pyrophosphate is believed to bind preferentially to calcium in the solid phase rather than in the solution phase, as it affected crystal morphology at very low concentrations and was detected on the crystals by X-ray microanalysis. Pyrophosphate seems to bind to the monohydrate but not to the dihydrate.

[The effect of magnesium on calcium oxalate crystal shapes generated with glycosaminoglycan]

Our previous report has shown that the shapes of calcium oxalate crystals formed in a supersaturated solution with glycosaminoglycan varied with glycosaminoglycan species. The present study was conducted to demonstrate the effect of magnesium on the shapes of calcium oxalate crystals with glycosaminoglycan by optical and scanning electron microscopy. In the presence of magnesium, the phenomenon of the plate- or sheet-like crystals parallel growing on the surface of other crystals was observed with each glycosaminoglycan and was enhanced with hyaluronic acid, chondroitin sulfate, heparan sulfate or heparin, more marked in this order. On the other hand, with heparan sulfate or heparin the stratification of the plate-like crystals was observed, whereas with hyaluronic acid or chondroitin sulfate it was not observed. Moreover, the stratification of the crystals with heparin was stimulated more markedly with increasing magnesium concentrations, and the lamella-shaped crystals at low heparin concentrations in the presence of magnesium was similar to the crystals at high heparin concentrations. These results suggest that magnesium stimulates the effect of glycosaminoglycan on calcium oxalate crystal shapes.

[Development of a semi-closed underwater breathing apparatus, the "eOBA"]

Nippon Sanso K.K developed a compact semi-closed underwater breathing apparatus, the eOBA. It consists of a mouthpiece, manifold with a purge valve, two spring-loaded flexible tubes, a small CO2 absorbent canister (net wt. = 190g), and two compact high pressure bottles (50ccx2: 190kg/cm2: 80%O2, 20%N2) with a regulator which supplies the gas at the constant flow rate of 1.5 l/min and lasts for 10 min. Thus, a counterlung is not incorporated. However, spring-loaded tubes act as a counterlung since its volume increases to 3.5 l when fully inflated. Dives to a depth of 5m are also recommended because of no bypass valve. This new eOBA was tested using the mechanical breathing machine and CO2 supply system to the circuit. For the various combinations of tidal volumes (0.5-2.5 l) and respiratory rates (10-20 breaths/min), the pressure at the mouthpiece, respiratory volume and the CO2 level were continuously monitored. The CO2 absorption rates were then calculated. The thin sloping P-V loops demonstrate that the eOBA is a flow dependent type of apparatus. It was found that the external work of breathing (0.1 kg.m/l at 30 l/min) were allowable. The CO2 absorption rates were sufficient when minute ventilation increased to 30 l/min. Thus, results show that the eOBA must be suitable for shallow and short dives.

[The effect of glycosaminoglycans on calcium oxalate crystal formation]

The effect of glycosaminoglycans on calcium oxalate crystal formation in the supersaturated solution was studied by examining the size and shape of calcium oxalate crystals generated under an optical microscope. It was found that heparan sulfate and heparin were more effective growth inhibitors than chondroitin sulfate and hyaluronic acid at concentrations within their respective urinary range. With increasing calcium and/or glycosaminoglycans concentration in the solution, the degree of growth inhibition caused by glycosaminoglycans was enhanced. Calcium oxalate crystal shapes generated with various glycosaminoglycans varied with glycosaminoglycan species. One of the causes of those differences in the shape and degree of growth inhibition might be the structural differences between them, that is, the number of sulfate residue and O- or N-form they contain. Calcium oxalate crystal shapes in the presence of heparin or heparan sulfate at higher concentrations were similar to those of calcium oxalate monohydrate crystals in the urinary sediments of hyperoxaluric patients. These facts might suggest the possibility that heparin and/or heparan sulfate were present in the crystal forming region.

Effect of glycosaminoglycans on calcium oxalate crystal aggregation

We have examined the effect of some glycosaminoglycan species on the aggregation of calcium oxalate monohydrate crystal by means of a Coulter counter. Our results showed that hyaluronic acid stimulated the aggregation at low concentrations but inhibited it at higher concentrations, and that both chondroitin sulfate and heparan sulfate acted as inhibitors. Glycosaminoglycans seem, therefore, to have quite different effects on the calcium oxalate crystal aggregation within their individual range of urinary concentration.

[Urinary material affecting calcium oxalate monohydrate stone formation]

We previously reported that the low molecular and uronic acid-rich fractions in the urine from calcium oxalate stone formers promoted aggregation of calcium oxalate monohydrate seed crystals. In this study, we have demonstrated that lyophilized material of the fractions contains hyaluronic acid as a sole glycosaminoglycans, as well as acidic amino acid-rich proteins and urinary pigment which is supposed to combine with protein. It is known that hyaluronic acid is present in stone matrix, that calcium containing stones contain proteins rich in acidic amino acids, and that the external color of calcium oxalate monohydrate calculi is usually brownish. These facts correspond with our present results. Therefore, it is suggested that the urinary material promotes the calcium oxalate crystal aggregation, sticks the crystals together and is incorporated into the stone.

[Effect of urinary material and glycosaminoglycans on calcium oxalate monohydrate crystal aggregation]

We have examined by the coulter counter method whether some substances promote or inhibit calcium oxalate monohydrate crystal aggregation. The substances tested were hyaluronic acid, chondroitin sulfate and urinary lyophilized material of less than 10 k dalton fractions having aggregate activity. As a result, hyaluronic acid promoted aggregation at low concentrations but inhibited it at higher concentrations, and chondroitin sulfate only inhibited it. They seem, therefore, to have quite different effects, depending on their urinary concentrations, on calcium oxalate crystal aggregation process. However, urinary fractions only promoted aggregation in a dose-response manner. This promoting effect might be caused by not only hyaluronic acid that was contained in the fractions but also by some other promoters.