Purification and some properties of a xylanase from Aspergillus sydowii MG49

Aspergillus sydowii MG49 produces a 30-kDa exosplitting xylobiohydrolase during growth on xylan. A specific chemical modification and substrate protection analysis of purified xylanase provided evidence that tryptophan and carboxy and amino groups are present at the catalytic site of this enzyme. Thermal inactivation of the xylanase occurs because of irreversible polymolecular aggregation, which is slower in the presence of glycerol.     

Chemical control of superconducting properties of (Y,Ca)(Sr,Ba)2Cu2.7Ga0.3O7−δ

The partial substitution of Ga at the Cu(1) (chain) sites of the YBa₂Cu₃O₇ structure allows synthesis at ambient pressure of Ba-free analogs, e.g., YSr₂Cu_2.7Ga_0.3O_7?δ . Materials with this composition have been found to be nonsuperconducting, but superconductivity has been induced by one or more of the following methods: Ca substitutions at the Y site; Ba substitutions at the Sr site; annealing in high-pressure oxygen. The influence of these chemical manipulations onT _c has been monitored and all methods have been found to enhanceT _c . The electronic effects of Ba substitutions have been deduced indirectly using powder neutron diffraction, and such substitutions appear to result in a redistribution of hole density into the Cu(1) sites from the superconducting CuO₂ planes.     

A prototype 3D optically interconnected neural network

We report the implementation of a prototype three-dimensional (3D) optoelectronic neural network that combines free-space optical interconnects with silicon-VLSI-based optoelectronic circuits. The prototype system consists of a 16-node input, 4-neuron hidden, and a single-neuron output layer, where the denser input-to-hidden-layer connections are optical. The input layer uses PLZT light modulators to generate optical outputs which are distributed over an optoelectronic neural network chip through space-invariant holographic optical interconnects. Optical interconnections provide negligible fan-out delay and allow compact, purely on-chip electronic H-tree type fan-in structure. The small prototype system achieves a measured 8-bit electronic fan-in precision and a calculated maximum speed of 640 million interconnections per second. The system was tested using synaptic weights learned off system and was shown to distinguish any vertical line from any horizontal one in an image of 4×4 pixels. New, more efficient light detector and small-area analog synapse circuits and denser optoelectronic neuron layouts are proposed to scale up the system. A high-speed, feed-forward optoelectronic synapse implementation density of up to 10⁴/cm² seems feasible using new synapse design. A scaling analysis of the system shows that the optically interconnected neural network implementation can provide higher fan-in speed and lower power consumption characteristics than a purely electronic, crossbar-based neural network implementation     

Intestinal obstruction and peritoneal carcinomatosis after endoscopic resection of transitional carcinoma of urinary bladder

Gut involvement in bladder tumours is low, even exceptional in the presence of surface, low-grade neoplasia. The authors explain their experience in the diagnosis and management of a patient treated endoscopically for a vesical surface tumour which subsequently exhibited peritoneal and gut metastatic seeding. The various mechanisms for gut dissemination of vesical neoplasias and the repercussion of their endoscopic management are discussed.     

The Continuous Interpolating Self-organizing Map

The self-organizing map (SOM) [5] provides a general data approximation method which is suitable for several application domains. The topology preservation is an important feature in data-analysis and may also be advantageous for the evaluation of the data in a function approximation or regression task. For this reason the interpolated self-organizing map (I-SOM) adds an output layer to the SOM architecture which computes a real valued output vector. This paper presents an extension of I-SOM towards a continuous interpolation. It is compared to RBF and to the parametrized self-organizing map.     

Fault tree analysis in case of multiple faults, especially covered and uncovered ones

It is shown that by a proper adaptation of Boolean algebra, multiple faults can be modeled for a subsequent fault tree analysis in an exceptionally convenient way. Specifically, the problem of properly modeling coverage can be solved satisfactorily. The approach is not only very simple to understand, but also, due to symbolic calculations, very attractive in cases where many sets of input parameters are to be processed quickly. (Note that this is not a paper on multi-valued analysis.)     

Endosonographic features of esophageal granular cell tumors

BACKGROUND AND STUDY AIMS: Granular cell tumors of the esophagus are rare tumors. A definite diagnosis is achieved by endoscopic biopsies in only 50% of cases. Endoscopic ultrasonography (EUS) is the best procedure in the evaluation of upper gastrointestinal tract submucosal tumors. The aim of this study was to describe the endosonographic findings of esophageal granular cell tumors. METHODS: From January 1989 to March 1994, 15 patients with 21 granular cell tumors which had negative biopsies were examined by EUS (Olympus GF UM3 or GF UM20,7,5 and 12 MHz). In five cases, the tumor was also studied with a 20 MHz Olympus miniprobe. The final histological diagnoses were obtained by subsequent endoscopic snare resection in 20 cases and surgically in one case. RESULTS: The endosonographic features (with the GF UM3 or GF UM20) of esophageal granular cell tumors were: a) a tumor size of less than 2 cm in 95% of cases; b) an hypoechoic solid pattern in 100% of cases; c) a tumor arising in the inner layers in 95% (second echo-poor layer n=15; third echo-rich layer n=5). In one case, the endosonographic finding was transmural malignant infiltration of the esophageal wall (histologically confirmed). CONCLUSION: When a granular cell tumor of the esophagus is suspected, EUS can show the inner layer location of the tumor and thus contribute to planning the endoscopic resection or follow up. When the tumor also invades the outer layers, EUS can contribute to planning the surgical resection.     

Perturbation in the 240Pu/239Pu global fallout ratio in local sediments following the nuclear accidents at Thule (Greenland) and Palomares (Spain)

Diabetes complicates 2-3% of all pregnancies and is associated with an increase in both perinatal morbidity and mortality, though reasons for these adverse outcomes are unknown. Estrogen biosynthesis is a critical factor during pregnancy and is carried out in the placenta via aromatase (cytochrome P450 19A1), which catalyzes the conversion of C-19 androgens to C-18 estrogens. Previous studies have shown that hormones such as insulin-like growth factors and insulin regulate aromatase activity when studied in vitro. Interestingly, levels of these hormones are altered in patients with diabetes. Thus, we hypothesized that the presence of maternal diabetes may alter placental aromatase activity and thus estrogen biosynthesis, possibly serving as one factor in the adverse outcomes of babies born to mothers with diabetes. To this end, we measured the production of 19-hydroxyandrostenedione, 19-oxoadrostenedione and estrone in 30 placental tissues from diabetic patients, using [7-3H]androst-4-ene-3,17-dione as a model substrate for aromatase (P450 19A1). A statistical difference was detected in the percentage of 19-oxoandrostenedione formed between the overt and control groups (P < 0.05). Additionally, NADPH P450-reductase levels were measured in these same tissues to determine whether alterations in this enzyme necessary for aromatase activity could be affected by diabetes. No differences in reductase levels were detected among the patient groups. However, a statistical correlation was found between NADPH P450-reductase activity and the formation velocities of all three estrogen products (P < 0.05). Thus, it appears that the presence of diabetes does not affect placental aromatase activity.     

Etoposide-induced PC12 cell death: apoptotic morphology without oligonucleosomal DNA fragmentation or dependency upon de novo protein synthesis

Etoposide, a topoisomerase II inhibitor used in cancer therapy, has been shown to induce apoptosis in vitro in a variety of cell types. In the present study, we have characterized the effects of etoposide on undifferentiated rat pheochromocytoma PC12 cells. Etoposide killed PC12 cells in a time- and concentration-dependent manner. 20-24 h incubation with 10 micrograms/ml etoposide induced 25-50% cell death. Hoechst 33258 staining revealed apoptotic morphology in dying cells. No evidence was found of either oligonucleosomal DNA fragmentation, as shown by agarose gel electrophoresis, or endonuclease involvement, as shown by the inability of aurintricarboxylic acid to prevent cell death. Cycloheximide and actinomycin-D were unable to prevent etoposide cytotoxicity indicating that the process is not dependent upon de novo protein or mRNA synthesis. NGF (5 ng/ml) prevented etoposide-induced PC12 cell death. These results offer an example of how the morphological features of apoptosis are not necessarily associated with oligonucleosomal DNA fragmentation or with de novo macromolecule synthesis.