Oral administration of antigen does not influence the proliferation and IFN-γ production of responsive CD8+ T cells but enables to establish T cell clones with different lymphokine production profile.

Feeding of a whole casein diet, which abolished the α_s1-casein-specific proliferation and IFN-γ productivity of CD⁴⁺ T cells, did not affect the proliferative response of CD8⁺ T cells with regard to the antigen dose response, cell dose response, kinetics of the proliferation and epitope specificity, as well as IFN-γ production. To assess the characteristics of the CD8⁺ T cells, we established α_s1-casein-specific CD8⁺ T cell clones from both casein-fed and control mice. The established clones produced different amount of IFN-γ and IL-10, and one clone derived from the casein-fed mice produced a remarkable amount of IL-10. The clones from casein-fed mice produced considerable amounts of TGF-β, while those from control mice produced only small amounts. The possible role of CD8⁺ T cells in oral tolerance is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mouse {beta}-galactoside {alpha}2,3-sialyltransferases: comparison of in vitro substrate specificities and tissue specific expression

Four types of ß-galactoside     

Expression of neural cell adhesion molecule (N-CAM) in perisinusoidal stellate cells of the human liver

Neural cell adhesion molecule (N-CAM) is distributed in most nerve cells and some non-neural tissues. The present immunohistochemical study has revealed, for the first time, the expression of N-CAM in perisinusoidal stellate cells of the human liver. Liver specimens were stained with monoclonal antibody against human Leu19 (N-CAM) by a streptoavidin-biotin-peroxidase-complex method. Light- and electron-microscopic analyses have shown that N-CAM-positive nerve fibers are distributed in the periportal and intermediate zones of the liver lobule. Perisinusoidal stellate cells in these zones are also positive for N-CAM. N-CAM is expressed on the surface of the cell, including cytoplasmic projections. Close contact of N-CAM-positive nerve endings with N-CAM-positive stellate cells has been observed. On the other hand, stellate cells in the centrilobular zone exhibit weak or no reaction for N-CAM. Perivascular smooth muscle cells and fibroblasts in the portal area and myofibroblasts around the central veins are negative for N-CAM. The present results indicate that the perisinusoidal stellate cells in the periportal and intermediate zones of the liver lobule characteristically express N-CAM, unlike other related mesenchymal cells, and suggest that the intralobular heterogeneity of N-CAM expression by stellate cells is related to the different maturational stages of these cells.     

Intraspecific brood-mixing of the cichlid fishPerissodus microlepis in Lake Tanganyika

Synopsis The frequency and origin of intraspecific brood-mixing in the biparental cichlid fishPerissodus microlepis were investigated by the cohort analysis of schooling young and the underwater observation of guarding parents. The cohort analysis showed that brood-mixing started from the early guarding state when the young were smaller than 10 mm standard length and nearly all schools of young larger than 16 mm contained alien young from up to 6 broods. Brood farming-out of this fish, which was originally proposed to be a way adopted only by a deserted parent, was performed also by paired parents. We suggest that brood-mixing inP. microlepis is attributed mainly to brood farming-out by paired and deserted parents.     

Bsr-REMI: An improved method for gene tagging using a new vector inDictyostelium

Using a plasmid pBsr2 which carries a blasticidin S-resistant gene, we have improved the method of REMI (restriction enzyme-mediated integration) provided for insertional mutagenesis inDictyostelium discoideum (bsr-REMI). To confirm usefulness of thebsr-REMI, transformation efficiency, copy number of integrated DNA, and randomness of integration into genome were examined.     

Enhancement of tryptophan production by Escherichia coli as an application of genetic engineering

Summary A feedback resistant trp operon plasmid that transformed a multiple mutant (trpR tnaA) of Escherichia coli was found to enhance remarkably the production of tryptophan in a bench-scale fermentor. 5.5 g of tryptophan was accumulated per litre of culture medium at 24th hr in batch. The productivity was 0.229 g/l/hr. This productivity is the highest among those ever reported by other workers. The recombinant plasmid (Tc^r Trp⁺ I^-) used was completely stable in each run when tetracycline was added by 10 g/l into the medium.     

Enhancement of penicillin acylase activity by cultivating immobilized Kluyvera citrophila

Summary Whole cells of Kluyvera citrophila were immobilized in polyacrylamide gel. The penicillin acylase activity of immobilized whole cells was 60%–70% of native cells. When the immobilized cells were continuously cultivated for 40 h in an aerated fermentor containing peptone medium and were treated with alkali in order to remove -lactamase activity, the immobilized cells produced ampicillin up to 4.4 times faster than noncultivated cells.Ampicillin production was investigated in a column system using these cultivated immobilized whole cells. The cultivated immobilized cells showed excellent performance in continuous ampicillin production.     

A specific microbial sensor for formic acid

Summary A microbial sensor consisting of immobilized Clostridium butyricum, two gas permeable Teflon membranes and fuel cell type electrode was suitable for the determination of formic acid. When the sensor was inserted into the sample solution containing formic acid, the current increases to a steady state with a response time of 20 min. The relationship between the steady state current and the formic acid concentration is linear up to 1 000 mg l^–1. The currents are reproducible with an average relative error of 5%. Selectivity of the sensor is satisfactory. Results obtained with this sensor and by gas chromatography were in good agreement (regression coefficient; 0.98) when the cultivation medium of Aeromonas formicans was employed. Immobilized Clostridium butyricum is stable for more than 20 days.     

Nitrogen fixation by immobilized Azotobacter chroococcum

A nitrogen-fixing bacterium, Azotobacter chroococcum, was immobilized in 2% agar gel. The optimum partial oxygen pressure, pO₂, of immobilized cells was 0.2 atm, wherea s that of native cells was 0.05 atm. When continual nitrogen fixation was performed under aerobic conditions, the nitrogenase activity of immobilized cells increased with increasing time. On the other hand, the activity of native cells decreased rapidly. Increase of nitrogenase activity was attributed to growth of the bacteria in the gel matrix. The production rate of total nitrogen compounds by the immobilized bacteria was also increased during the first 4 days. Nitrogen compounds produced by the immobilized cells were mainly amino acids such as γ-aminobutyrate, glutamate and arginine.