Characterization of the microbial community in an anaerobic ammonium-oxidizing biofilm cultured on a nonwoven biomass carrier

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.     

Behaviour of chromium steels in liquid Pb-55.5Bi with changing oxygen content and temperature

The behaviour of protective oxide layers on P122 steel and its welds and of ODS steel in liquid Pb_44.5Bi_55.5 (LBE) is examined under conditions of changing temperatures and oxygen concentrations. P122 (12Cr) and its welded joints are exposed to LBE at 550 °C for 4000 h with oxygen concentrations of 10⁻⁶ and 10⁻⁸ wt% (p(O₂) = 8.1 × 10⁻²³ bar and 5.2 × 10⁻²⁷ bar) which change every 800 h. It is found that like in case of constant oxygen concentration of 10⁻⁶ wt% a protective spinel layer (Fe(Fe_1−xCr_x)₂O₄) was maintained on P122 and also on its welded joint. Two experiments with exposure times of 4800 h are conducted on ODS steel, both with temperatures changing from 550 to 650 °C and back every 800 h, one experiment with 10⁻⁶ the other with 10⁻⁸ wt% oxygen in LBE. Both experiments show strong local dissolution attack after 4800 h which is in agreement with the behaviour of ODS in LBE at a constant temperature of 650 °C. However, dissolution attack is less in LBE with 10⁻⁸ wt% oxygen (p(O₂) = 3.0 × 10⁻²⁵ bar).     

An Experimental Study of a Cooperative Positioning System

Several position identification methods are being used for mobile robots. Dead reckoning is a popular method but due to the error accumulation from wheel slippage, its reliability is low for measurement of long distances especially on uneven surfaces. Another popular method is the landmark method, which estimates current position relative to known landmarks, but the landmark method's limitation is that it cannot be used in an uncharted environment. Thus, this paper proposes a new method called Cooperative Positioning System (CPS) that is able to overcome these shortcomings. The main concept of CPS is to divide the robots into two groups, A and B where group A remains stationary and acts as a landmark while group B moves and then group B stops and acts as a landmark for group A. This process is repeated until the target position is reached. Compared with dead reckoning, CPS has a far lower accumulation of positioning errors, and can also work in three dimensions. Furthermore, CPS employs inherent landmarks and therefore can be used in uncharted environments unlike the landmark method. In this paper, we introduce the basic concept of CPS and its positioning principle. Next, we outline a second prototype CPS machine model (CPS-II) and discuss the method of position estimation using the variance of positioning error and weighted least squares method. Position identification experiments using the CPS-II model give a positioning accuracy of 0.12% for position and 0.32 degree for attitude after the robots traveled a distance of 21.5 m.     

Expression of DCC protein in colorectal tumors and its relationship to tumor progression and metastasis

The strains BALB/cHeA (BALB/c) and STS/A (STS) differ in production of IL-4 and IL-10, two Th2 cytokines, after stimulation of spleen cells with Concanavalin A, STS being a low and BALB/c a high producer. We analyzed the genetic basis of this strain difference using the recombinant congenic (RC) strains of the BALB/c-c-STS/Dem (CcS/Dem) series. This series comprises 20 homozygous strains. Each CcS/Dem strain contains a different, random set of approximately 12. 5% genes of the "donor" strain STS and approximately 87.5% of the "background" strain BALB/c. We selected for further analysis the RC strain production intermediate between BALB/c and STS. In (CcS-20xBALB/c)F2 hybrids we found that different loci control expression of IL-4 and IL-10. Cypr1 (cytokine production 1) on chromosome 16 near D16Mit15 controls IL-4 production, whereas the production of IL-10 is influenced by loci Cypr2 near D1Mit14 and D1Mit227 on chromosome 1 and Cypr3 marked by D5Mit20 on chromosome 5. In addition, the relationship between the level of these two cytokines depends on the genotype of the F2 hybrids at a locus cora1 (correlation 1) on chromosome 5. This differential genetic regulation may be relevant for the understanding of biological effects of T-helper cells in mice of different genotypes.     

Mobile catabolic genes in bacteria

The recent findings of various mobile catabolic genes have provided some insight into the evolution of microbial degradation systems for xenobiotic compounds. The catabolic genes undergo marked genetic rearrangements due to their presence on transposons or association with mobile genetic elements. Bacterial catabolic transposons fall into three defined structural classes. Class I elements include catabolic genes flanked by two copies of insertion sequences. Class II elements carry short terminal inverted repeats and transpose by the replicative mode in which transposase and resolvase are involved. Conjugative catabolic transposons represent the third class of mobile genetic elements. They carry all the genes required for excision, conjugal transfer to a new host, and integration. This review focuses on the structures, functions and roles of the recently characterized catabolic transposons in bacteria. Also described are the mobile catabolic elements that share structural similarity with the pathogenicity and symbiosis islands.     

Properties of the peptides liberated from rice protein in sokujo-moto

In the supernatant of sokujo-moto, a high level of acid carboxypeptidase (ACP) activity and a large amount of peptides were observed, however, the amount of free amino acids liberated was small. In order to determine why these peptides were not hydrolyzed to any significant degree by the ACP, the properties of the peptides in sokujo-moto were investigated in this study. Peptides were fractionated from sokujo-moto by ion exchange column chromatography. ACP purified from rice-koji (rice overgrown with Aspergillus oryzae) was allowed to react with the peptides, and it was found that they were not hydrolyzed to any significant degree by the enzyme. Gel filtration chromatography was performed to ascertain the molecular size distribution of the peptides in sokujo-moto, and it was revealed that they were of low molecular sizes; molecular size: mainly in the range of 200-400, and chain length: 2-3. ACP purified from rice-koji was also allowed to react with various synthetic peptides, and it was found that ACP of rice-koji could not rapidly hydrolyze low-molecular-size peptides, such as dipeptides or tripeptides. Acid protease (AP) purified from rice-koji released peptides of molecular sizes mainly in the range of 300-600 or above from rice protein under acidic conditions (pH 3.6; the pH of sokujomoto). When AP and ACP were allowed to act at the same time on rice protein, mainly low-molecular-size peptides (molecular sizes mainly in the range of 200-400) were produced. From these results, it was estimated that AP released peptides with molecular sizes mainly in the range of 300-600 or above from rice protein and ACP degraded the relatively higher molecular size peptides among them to lower molecular size peptides; consequently only low-molecular-size peptides with molecular sizes mainly in the range of 200-400 were released in the supernatant of sokujo-moto.     

Optical matching of a slowly extracted beam with transport line

In order to define the optical parameters of a slowly extracted beam at the entrance of the extraction channel and to realize optical matching with the beam line, the outgoing separatrix was measured at HIMAC. Modifying the lattice parameters of the ring model according to the measurement result, the simulation result makes it possible to predict the optical parameters at the extraction channel. As a result, it was experimentally verified that optical matching of the slowly extracted beam with the transport line was realized. The measured beam size and dispersion functions were in good agreement with the calculation result at each monitor in the transport line. Particle tracking also predicts the beam profile at each profile monitor in the beam line. Further, a quasi-parallel beam was demonstrated by changing the beam optics in the beam line.     

Adjuvant intra-arterial chemotherapy with gastrin receptor antagonist after hepatic resection in colorectal cancer metastasis

The aim of this study was to determine whether chemo-endocrine therapy after the resection of liver metastasis from colorectal cancer would prevent recurrence in the remnant liver and prolong survival. Eleven colorectal cancer patients underwent hepatic resection for liver metastasis. Subsequently, they were administered Proglumide gastrin antagonist 1,200 mg/day + 5'-DFUR 800 mg/day for 2 years. In seven of them, MMC 6-10 mg and ADM 20 mg were infused intra-arterially every two weeks alternately for one year. In four of them, 5-FU 250 mg/day was infused for seven days continuously intra-arterially every two weeks for one year. Recurrence in the remnant liver occurred in four of 11 patients. All of these patients underwent repeated hepatectomy. The mean disease-free survival in the remnant liver was 37 months and the five-year survival rate was 91%. These results indicate that intra-arterial chemotherapy with gastrin receptor antagonist might be effective for adjuvant therapy in patients with resectable liver metastasis from colorectal cancer.     

Elimination of artifacts in MRCP: technical consideration

Artifacts of MR cholangiopancreatography (MRCP) include fluid-filled gastrointestinal tracts, respiratory motion artifacts, spasm of Oddi's sphincter, vascular compression of bile ducts, overlapping of various anatomical structures and bright signal of surrounding fatty tissue. In this article, various technical considerations to eliminate these artifacts were described for the better imaging analysis of MRCP. The use of high-concentration ferric ammonium citrate (Ferriseltz) is recommended to reduce bright signal of fluid-filled gastrointestinal tracts. In case of long breathhold sequences, O2-inhalation study is useful to eliminate respiratory motion artifacts. Careful attention should be paid to the spasm of Oddi's sphincter and the vascular compression of bile ducts to avoid erroneous interpretation of MRCP findings.