Thermobalance hydropyrolysis of a bituminous coal sample and its macerals vitrinite and exinite: structural analysis of the relevant tars

Thermobalance hydropyrolysis experiments are carried out on a highly volatile coal sample and its main macerals, vitrinite and exinite. The results are discussed according to the characterization of the tars using ultrasound solvent extractions, extrography, liquid chromatography, capillary gas chromatography and mass spectrometry.     

Design, synthesis and evaluation of transition-state analogue inhibitors of Escherichia coli gamma-glutamylcysteine synthetase

Phosphinic acid-, sulfoximine- and sulfone-based transition-state analogues were synthesized and evaluated as inhibitors of Escherichia coli gamma-glutamylcysteine synthetase. These compounds have a carboxyl function at the beta-carbon to the tetrahedral central hetero atom so as to mimic the carboxyl group of the attacking cysteine in the transition state. The phosphinic acid- and the sulfoximine-based compounds were found to be potent ATP-dependent inactivators, both showing a slow-binding kinetics with overall affinities and second-order inactivation rates of one to two orders of magnitude greater than those of L-buthionine (SR)-sulfoximine (L-BSO). The sulfone was a simple reversible inhibitor without causing ATP-dependent enzyme inactivation, but its affinity toward the enzyme was still five times greater than that of L-BSO, indicating that the beta-carboxyl function plays a key role in the recognition of the inhibitors by the enzyme. The sulfoximine with (S)-beta-carbon to the sulfur was synthesized stereoselectively, and the two diastereomers with respect to the chiral sulfur atom were separated as a cyclic sulfoximine derivative. The sulfoximine with R-configuration around the sulfur served as an extremely powerful ATP-dependent inactivator with an overall inhibition constant of 39 nM and an inactivation rate of 6750 M-1 s-1, which correspond to 1260-fold higher affinity and almost 1400-fold greater inactivation rate as compared with L-BSO. The sulfoximine with (S)-sulfur was a simple reversible inhibitor with an inhibition potency comparable to that of the sulfone. The synthesis and inhibition profile of the N-phosphoryl sulfoximine is also described.     

Comparison of carbohydrate structures of serum alpha-fetoprotein by sequential glycosidase digestion and lectin affinity electrophoresis

Serum alpha-fetoprotein (AFP) is a glycoprotein of which the sugar chain is considered to show structural changes with malignancies. Microheterogeneity of the serum AFP carbohydrate structure was studied in samples from 35 patients with benign and malignant diseases. Sera were digested directly, extensively, and sequentially with sialidase. beta-galactosidase and beta-N-acetylhexosaminidase. Before and after digestion, sera were examined by means of lectin affinity electrophoresis using eight lectins. Relationships between AFP carbohydrate structures and liver diseases were elucidated by the lectin-reactive profiles and the effect of glycosidase digestion. More than 94% of the AFP carbohydrate structures found in patients with benign and malignant liver diseases were biantennary complex-type oligosaccharides. Changes in the AFP carbohydrate structures at the early stage of hepatocellular carcinoma revealed the addition of alpha 1-->6 fucose to the reducing terminal N-acetylglucosamine and monosialylated AFPs. In both advanced hepatocellular carcinoma and AFP producing extrahepatic malignancies, AFP carbohydrate structures were characterized as the further addition of beta 1-->4 N-acetylglucosamine and heterogeneity in the galactose and N-acetylglucosamine residues. Sequential glycosidase digestion and lectin affinity electrophoresis is useful for analysing the carbohydrate structures of serum glycoprotein.     

A cautious scheduler for multistep transactions

Given a classC of serializable schedules, a cautiousC-scheduler is an on-line transaction scheduler that outputs schedules in classC and never resorts to rollbacks. Such a scheduler grants the current request if and only if the partial schedule it has granted so far, followed by the current request, can be extended to a schedule inC. A suitable extension is searched among the set of all possible sequences of the pending steps, which are predeclared by the transactions whose first requests have already arrived. If the partial schedule cannot be extended to a schedule inC, then the current request is delayed. An efficient cautiousCPSR-scheduler has been proposed by Casanova and Bernstein. This paper discusses cautiousWRW-scheduling, whereWRW is the largest polynomially recognizable subclass of serializable schedules currently known. Since cautiousWRW-scheduling is, in general, NP-complete as shown in this paper, we introduce, a subclass (namedWRW ^#) ofWRW and discuss an efficient cautiousWRW ^#-scheduler. We also show that the fixed point set of the cautiousWRW ^#-scheduler properly containsCPSR. Therefore, ourWRW ^#-scheduler allows more concurrency than anyCPSR- scheduler.     

Bay K 8644 increases resting Ca2+ spark frequency in ferret ventricular myocytes independent of Ca influx: contrast with caffeine and ryanodine effects

Bay K 8644, an L-type Ca2+ channel agonist, was shown previously to increase resting sarcoplasmic reticulum (SR) Ca2+ loss and convert post-rest potentiation to decay in dog and ferret ventricular muscle. Here, the effects of Bay K 8644 on local SR Ca2+ release events (Ca2+ sparks) were measured in isolated ferret ventricular myocytes, using laser scanning confocal microscopy and the fluorescent Ca2+ indicator fluo-3. The spark frequency under control conditions was fairly constant during 20 s of rest after interruption of electrical stimulation. Bay K 8644 (100 nmol/L) increased the spark frequency by 466+/-90% of control at constant SR Ca2+ load but did not change the spatial and temporal characteristics of individual sparks. The increase in spark frequency was maintained throughout the period of rest. The increase in Ca2+ spark frequency induced by Bay K 8644 was not affected by superfusion with Ca2+-free solution (with 10 mmol/L EGTA) but was suppressed by the addition of 10 micromol/L nifedipine (which by itself did not alter resting Ca2+ spark frequency). This suggests that the effect of Bay K 8644 on Ca2+ sparks is mediated by the sarcolemmal dihydropyridine receptor but is also independent of Ca2+ influx. Low concentrations of caffeine (0.5 mmol/L) increased both the average frequency and duration of sparks. Ryanodine (50 nmol/L) increased the spark frequency and also induced long-lasting Ca2+ signals. This may indicate long-lasting openings of SR Ca2+ release channels and a lack of local SR Ca2+ depletion. In lipid bilayers, Bay K 8644 had no effect on either single-channel current amplitude or open probability of the cardiac ryanodine receptor. It is concluded that Bay K 8644 activates SR Ca2+ release at rest, independent of Ca2+ influx and perhaps through a functional linkage between the sarcolemmal dihydropyridine receptor and the SR ryanodine receptor. In contrast, caffeine and ryanodine modulate Ca2+ sparks by a direct action on the SR Ca2+ release channels.     

Experimental study of tracheal patch reconstruction with a covered expandable metallic stent

BACKGROUND: We evaluated the efficacy of tracheal patch reconstruction with a covered expandable metallic stent (EMS) with omentoplasty. METHODS: After resecting the right half of the circumferential wall of two tracheal rings in adult beagle dogs, we inserted a covered EMS to reconstruct the defect interiorly. Then, through laparotomy, we made an omental pedicle flap and wrapped it around the EMS-interposed area. For comparison with the group without omentoplasty, we periodically examined the healing process macroscopically and histologically. RESULTS: Bronchofiberscopic observations revealed that incorporation of the covered EMS progressed with the passage of time and tracheal luminal patency was maintained well in both groups. However, polyplike granulation developed gradually at both ends of the EMS. Histologically, epithelium was regenerated in the patched area 4 weeks postoperatively and the area was covered with pseudostratified ciliated epithelium at 12 weeks postoperatively. Quantitative analysis of the macroscopic and histologic findings showed that the inflammatory polyps were reduced and epithelialization was promoted in the group with omentoplasty. CONCLUSIONS: Tracheal patch reconstruction with a covered EMS, when combined with omentoplasty, promoted early epithelial regeneration and suppressed the development of inflammatory polyps.     

Action of phenolic antioxidants on various active oxygen species

The action of phenolic antioxidants, such as probucol, on various active oxygen species was investigated using luminol chemiluminescence and spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The various active oxygen species, including hydroxyl radicals (Fenton reaction), superoxide anions, singlet oxygen and hypochlorite ions were examined with phenolic antioxidants under aqueous and nonaqueous conditions. Probucol showed a quenching effect on both superoxide anions and hypochlorite ions in nonaqueous solution. However, it had no effect on hydroxyl radicals. alpha-Tocopherol, a natural phenolic antioxidant, showed a stronger quenching effect on superoxide anions and hypochlorite ions than probucol, and quenched hydroxyl radicals in nonaqueous solution. Furthermore, Trolox showed a quenching effect on all active oxygen species in both aqueous and nonaqueous solution. The antioxidants were studied under comparable conditions in a series of test systems and the reactivity profiles depicted as 'radar charts' which are helpful for characterizing antioxidant action.     

Bending strength of pulp cement board composed of separated pulp from municipal solid waste

The relation between bending strength and X-ray diffraction intensity for pulp cement board composed of separated pulp from municipal solid waste was studied. Higher bending strength was observed for the boards with higher diffraction intensity of Ca(OH)₂. Lower bending strength at the same diffraction intensity was observed for the boards from coarsely separated pulps than those from other pulps used. This difference in bending strength was discussed in relation to the differences in the strength of pulp and the amount of fine fraction in pulp.