Primary structure of three mannosyl-glycoasparagines and nine sialyl-oligosaccharides isolated from the urine of two patients with Gaucher''s disease (infantile form)

Initial-rate measurements were made of the reduction of pyridine-3-aldehyde and p-carboxybenzaldehyde by NADPH catalyzed by pig liver aldehyde reductase I. The initial velocity analysis and product inhibition data suggest that aldehyde reductase I obeys a compulsory-order mechanism with pyridine-3-aldehyde as substrate but follows a partially random-order pathway with p-carboxybenzaldehyde. The partially random-order pathway would be operative only at high concentrations of p-carboxybenzaldehyde. In both cases, aldehydes and the corresponding alcohol substrates inhibit the enzyme at high concentration. Abortive ternary complexes are shown to be formed with pyridine-3-aldehyde and with p-carboxybenzaldehyde. Dissociation of the coenzyme from the abortive ternary complex seems only to be observed with p-carboxybenzaldehyde. This study suggests overall that an enzyme kinetic mechanism may be different, depending on whether specific interactions can occur between certain amino acid residue(s) of the protein active site and substrates. Finally, the mechanism of the inhibition of pyridine-3-aldehyde reduction by diacid derivatives is discussed.     

Iron content of sediment and phosphate adsorption properties

Phosphorus can occur in sediments in different forms and accordingly its availability varies. The distinction between the phosphorus fractions is made with two chemical extraction methods; an ammonium oxalate-oxalic acid extraction and an extraction according to Hieltjes & Lijklema (1980).The iron and aluminum liberated with the ammonium oxalate-oxalic acid extraction method is linearly correlated (r ² = 0.73) with the phosphorus liberated in the first two steps of the Hieltjes and Lijklema extraction by: P = 0.035 (Fe + Al) + 0.001 (P, Fe and Al in mmol g^–1).The iron and aluminum (hydr)oxides are very important fractions in the sediment adsorption capacity for phosphorus. The phosphorus sorption capacity (PSC) is 0.080 mol P (mol (Fe + Al))^–1 and the adsorption constant (k) is 11.9 µmol P l^–1. Here it is assumed that iron and aluminum (hydr)oxide have the same affinity for phosphorus.     

Chemical behaviour of cytidine 5'-monophospho-N-acetyl-beta-D-neuraminic acid under neutral and alkaline conditions

The chemical behaviour of CMP-N-acetylneuraminic acid under neutral and different alkaline conditions has been investigated. The products formed were isolated by ion-exchange chromatography and gel filtration and analysed by colorimetric methods, thin-layer chromatography, combined gas-liquid chromatography/mass spectrometry and/or 360-MHz 1H-NMR spectroscopy. A maximum stability of CMP-N-acetylneuraminic acid was observed at pH8-11. In the tested pH range of 6-13, CMP and N-acetylneuraminic acid were formed in variable amounts as decomposition products. 2-Deoxy-2,3-dehydro-N-acetylneuraminic acid was produced at pH greater than 7; the amount of this substance increased with increasing pH. In anhydrous triethylamine its yield was 50%. A new neuraminic acid derivative, N-acetyl-beta-D-neuraminic acid 2-phosphate, could be isolated from the mixture of alkaline decomposition products of CMP-N-acetylneuraminic acid. The yield of this compound was maximum 22% in anhydrous triethylamine. Because 2-deoxy-2,3-dehydro-N-acetylneuraminic acid was formed under simulated physiological conditions, it is assumed that this compound, which occurs in tissues and fluids of man and animals, is derived from CMP-N-acetylneuraminic acid non-enzymically also under conditions in vivo.     

The structure of sialyl-glycopeptides of the O-glycosidic type, isolated from sialidosis (mucolipidosis I) urine

Plants performing crassulacean acid metabolism show a large nocturnal accumulation of malic acid in the vacuole of the photosynthetic cells. It has been postulated that an H+-translocating ATPase energizes the transport of malic acid across the tonoplast into the vacuole. In the present work we have characterized the ATPase activity associated with vacuoles of the crassulacean-acid-metabolism plant Kalancho? daigremontiana and compare it with other phosphohydrolases. Vacuoles were isolated by polybase-induced lysis of mesophyll-cell protoplasts. The vacuoles had a high activity of unspecific acid phosphatase (pH optimum 5.3). The acid phosphatase was strongly inhibited by ammonium molybdate (with 50% inhibition at about 0.5 mmol m-3), but was not completely inhibited even at much higher ammonium-molybdate concentrations. In contrast, the vacuolar ATPase activity, assayed in the presence of 100 mmol m-3 ammonium molybdate, had a pH optimum of 8.0. ATP was the preferred substrate, but GTP, ITP and ADP were hydrolyzed at appreciable rates. The mean ATPase activity at pH 8.0 was 14.5 nmol h-1 (10(3) vacuoles)-1, an average 13% of which was attributable to residual acid-phosphatase activity. Inorganic-pyrophosphatase activity could not be demonstrated unambiguously. The vacuolar ATPase activity was Mg2+-dependent, had an apparent Km for MgATP2- of 0.31 mol m-3, and was 32% stimulated by 50 mol m-3 KCl. Of the inhibitors tested, oligomycin slightly inhibited the vacuolar ATPase activity and diethylstilbestrol and NO-3 were both markedly inhibitory. Dicyclohexylcarbodiimide and tributyltin were also strongly inhibitory. Tributyltin caused a 50% inhibition at about 0.3 mmol m-3. This is taken as evidence that the vacuolar ATPase might function as an H+-translocating ATPase. It is shown that the measured activity of the vacuolar ATPase would be of the right order to account for the observed rates of nocturnal malic-acid accumulation in K. daigremontiana.     

Modelling sediment transport in shallow lakes — interactions between sediment transport and sediment composition

In shallow, wind exposed lakes, the light conditions, the cycling of nutrients, heavy metals and organic micro-pollutants and changes in the local composition of the sediment top layer can be dominated by resuspension/erosion of bottom sediment and sedimentation of suspended solids. A 2 dimensional model for Sediment Transport, Resuspension and Sedimentation in Shallow lakes (STRESS-2d), based on an existing transport model, is discussed. In the model, mass balance equations for the water compartment and the bottom sediment are solved numerically. Up to 7 sediment fractions can be taken into account, each having a specific set of resuspension/erosion and sedimentation parameter values. Several options for modelling the changes in the bottom sediment composition are available.A simulation experiment for Lake Veluwe (The Netherlands), in which model options with and without the distinction of sediment fractions were used, showed that using sediment fractions to account for the variability in the sediment composition leads to an improvement of the model results, particularly the simulated phosphorus sediment-water exchange fluxes. For Lake Ketel (The Netherlands) two options for modelling changes in the bottom sediment composition are compared. It is shown that an option in which a thin water-sediment layer on top of the more consolidated bottom sediment is simulated provides an improvement in the simulation of the suspended solids concentration.     

Primary structure of the asparagine-563-linked carbohydrate chain of an immunoglobulin M from a patient with Waldenstrom's macroglobulinemia. A reinvestigation by 500-MHz H-NMR spectroscopy

The activity of microsomal cholesterol 7α-hydroxylase is shown to be increased in vitro by ATP, Mg²⁺, and a cytosolic protein fraction. There was a loss of enzyme activity in the presence of E. coli alkaline phosphatase which was proportional to the amount of phosphatase. Much of this loss was recovered upon addition of ATP, Mg²⁺, and a cytosolic protein fraction.     

2-Acetamidoglucal, a new metabolite isolated from the urine of a patient with sialuria.

A new metabolite, namely 2-acetamidoglucal, has been found in the urine of a patient with sialuria in addition to the metabolites N-acetylneuraminic acid, N-acetylmannosamine, N-acetylglucosamine and 2-deoxy-2,3-dehydro-N-acetylneuraminic acid reported earlier. the structure has been identified by mass spectrometry and 360 MHz proton nuclear magnetic resonance spectroscopy and verified by synthesis. All accumulated compounds fit into the metabolic pathway for the biosynthesis of CMP-N-acetylneuraminic acid. Sialuria is discussed in terms of a failure of regulation of UDP-N-acetylglucosamine 2-epimerase.     

Receptor-mediated internalization and degradation of diphtheria toxin by monkey kidney cells.

The receptor-mediated internalization and degradation of radiolabeled diphtheria toxin by cultured monkey kidney cells was studied. The ability of a number of enzymes and chemicals to remove cell surface-bound toxin was tested; the combination of pronase and inositol hexaphosphate (PIHP) proved most effective. Using PIHP, the kinetics of toxin-cell association at 37 degrees C was resolved into two compounds: surface binding and internalization. The PIHP assay also allowed estimation of the half-time of toxin internalization (about 25 min). An assay involving precipitation of culture supernatants with trichloroacetic acid was developed and used to measure the rate of degradation and excretion of cell-associated toxin. Agents which markedly inhibited toxin internalization similarly prevented degradation, implying an intracellular location for the degradative process. The primary radioactive product excreted by Vero cells was monoiodotyrosine. The extent and rate of toxin degradation indicated lysosomal involvement. Finally, agents which blocked internalization or degradation, or both, (e.g. antibody and concanavalin A), protected cells from the cytotoxin action of diphtheria toxin, suggesting that these processes are necessary for expression of biological effect.     

Dance Choreography Is Coordinated with Song Repertoire in a Complex Avian Display

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Exposure of neural crest cells to elevated glucose leads to congenital heart defects, an effect that can be prevented by N-acetylcysteine

BACKGROUND: Diabetes mellitus during pregnancy increases the risk for congenital heart disease in the offspring. The majority of the cardiovascular malformations occur in the outflow tract and pharyngeal arch arteries, where neural crest cells are essential for normal development. We studied the effects of specific exposure of neural crest cells to elevated glucose on heart development. Antioxidants reduce the damaging effect of glucose on neural crest cells in vitro; therefore, we investigated the effect of supplementing N-acetylcysteine in vivo. METHODS: Cardiac neural crest of HH 8-12 chicken embryos was directly exposed by a single injection in the neural tube with 30 mM D-glucose (or 30 mM L-glucose as a control). To examine the effect of a reduction in oxidative stress, we added 2 mM N-acetylcysteine to the injected D-glucose. RESULTS: Exposure of neural crest cells to elevated D-glucose-induced congenital heart malformations in 82% of the embryos. In the embryos injected with L-glucose, only 9% developed a heart malformation. As expected, all malformations were located in the outflow tract and pharyngeal arch arteries. The frequency of heart malformations decreased from 82% to 27% when 2 mM N-acetylcysteine was added to the injected D-glucose. CONCLUSIONS: These data are the first to confirm that the vulnerability of neural crest cells to elevated glucose induces congenital heart malformations. The fact that N-acetylcysteine limits the teratogenicity of glucose implies that its damaging effect is mediated by an increase of oxidative stress in the neural crest cells.