MHC antigen expression by melanomas recovered from mice treated with allogeneic mouse fibroblasts genetically modified for interleukin-2 secretion and the expression of melanoma-associated antigens

Recent approaches toward the immunotherapy of neoplastic disease involve the introduction of expression-competent genes for interleukin-2 (IL-2) into autologous malignant cells. Treatment of tumor-bearing experimental animals with the IL-2-secreting cells successfully induces partial and at times complete remissions. In most instances, however, although delayed, progressive tumor growth continues. Here, certain of the characteristic of B16 melanomas (H-2^b) persisting in C57BL/6 mice (H-2^b) treated with an IL-2-secreting, melanoma-antigen-positive cellular immunogen (RLBA-IL-2 cells) are described. Unlike the melanoma cells first injected, B16 cells recovered from mice treated with RLBA-IL-2 cells were deficient in the experssion of MHC class I, but not class II determinants. Deficient MHC class I expression correlated with the cells' resistance to cytotoxic T lymphocytes (CTL) from the spleens of mice immunized with RLBA-IL-2 cells. Melanomas persisting in mice treated with non-IL-2-secreting, melanoma-antigen-positive cell constructs (RLBA-ZipNeo cells) were also deficient in the expression of MHC class I determinants, and the melanoma cells were resistant to CTL from mice immunized with RLBA-ZipNeo cells. Thus, the expression of melanoma-associated antigens rather than IL-2-secretion correlated with deficient MHC class I expression by the persistent melanomas. This point was substantiated by the expression of MHC class I antigens by melanomas persisting in mice treated with IL-2-secreting, melanoma-antigen-negative LM cells (LM-IL-2); it was equivalent to that of melanomas in untreated mice. The involvement of MHC class I antigens in the immune resistance of persistent melanoma cells from mice treated with the melanoma-autigen-positive immunogens was indicated by the effect of interferon (IFN) orN-methyl-N-nitro-N-nitrosoguanidine (MNNG) on the susceptibility of the cells to anti-melanoma CTL. Treatment of the resistant melanomas with IFN or MNNG stimulated MHC class I antigen expression and restored the cells' sensitivity to CTL from mice immunized with IL-2-secreting or nonsecreting, melanoma-antigen-positive cellular immunogens. Prior treatment of the treated cells with antibodies to MHC class I determinants inhibited the cells' susceptibility to CTL from mice immunized with RLBA-IL-2 cells.     

Production and initial characterisation of the xylan-degrading system of Phanerochaete chrysosporium

We report the optimum conditions for the degradation of oat spelt arabinoxylan and a preliminary characterisation of the inducible xylan-degrading system of the lignin-degrading white-rot fungus Phanerochaete chrysosporium. Xylanase activity was optimal at pH 5.0 and 50°C; see attached sheet the maximum reaction velocity (V_max) of the system was 3.86 units (U) mg^–1 protein with arabinoxylan as substrate and the substrate concentration giving half V_max (S_0.5) was 0.52 mg ml^–1. At concentrations of arabinoxylan greater than 15 mg ml^–1 excess substrate inhibition was observed. Xylose at 0.9 mm inhibited activity to the extent of 50%. Xylanase activity increased as a function of the dilution of the enzyme preparation prior to assay. It was resolved into four peaks by using a DEAE-Biogel column; the material in these peaks differed with respect to xylan solubilisation and the formation of reducing sugars. Electrofocusing gels allowed visualisation of several bands of activity corresponding to each peak. The arabinoxylan degradation system of P. chrysosporium is therefore composed of multiple components. Correspondence to: P. Broda     

Z → B transition in poly[d(G-m5C)2] induced by interaction with 4′,6-diamidino-2-phenylindole

The Z form of poly[d(G-m⁵C)₂], in presence of Mg²⁺ ion, is found to be transformed into B form upon interaction with 4′,6-diamidino-2-phenylindole (DAPI). The Z → B transformation is complete at a mixing ratio of about 0.07 DAPI per DNA base pairs, i.e., each DAPI molecule may be related to the conversion of 6–7 base pairs. An interaction between DAPI and poly[d(G-m⁵C)₂] in its Z form at low drug: DNA ratios is suggested from optical dichroism and time-resolved luminescence anisotropy results. The spectroscopic behaviour of DAPI indicates that the Z conformation of DNA does not provide normal binding sites for DAPI, such as groove or intercalation sites, but that the initial association may be of external nature. © 1993 John Wiley & Sons, Inc.     

Cytological and molecular characterization of a chromosome interchange and addition lines in Cadet involving chromosome 5B of wheat and 6Ag of Lophopyrum ponticum

Efforts to transfer wheat curl mite (Eriophyes tulipae Keifer) resistance from Lophopyrum ponticum 10X (Podb.) Love to bread wheat (Triticum aestivum L.) have resulted in the production of a number of cytogenetic stocks, including an addition line of 6Ag, a ditelo addition line, and a wheat-Lophopyrum translocation line. Characterization of these lines with C-banding, in situ hybridization with a Lophopyrum species-specific repetitive DNA probe (pLeUCD2), and Southern blotting with pLeUCD2 and a 5S ribosomal DNA probe (pScT7) confirmed that the distal portion of the short arm of 6Ag was translocated onto the distal portion of 5BS (5BL. 5BS-6AgS). It was also determined that the ditelo addition was an acrocentric chromosome of 6AgS.     

Mechancial properties of bat wing membrane skin

The skin of the bat wing in functionally unique among mammals: it serves as a major locomotor organ in addition to its protective and regulatory functions. We used tensile testing to investigate the mechanical capabilities of wing membrane skin, and compared stiffness, strength, load at failure, and energy absorption among specific wing regions and among a variety of bat taxa. We related these characteristics to the highly architectural fibrous supporting network of the wing membrane. We found that all material properties showed a strong anisotropy. In particular, wing membrane skin shows maximum stiffness and stregth parallel to the wing skeleton, and greatest extensibility parallel to the wing's trailing edge. We also found significant variation among wing regions. The uropatagium (tail membrane) supported the greatest load at failure, and the plagiopatagium (proximal wing membrane between laterl body wall and hand skeleton) is the weakest and most extensible part of the wing. We believe that the increased load bearing ability of the uropatagium relats to its key role in capture of insect prey, and that the great extensibility of the plagiopatagium promotes development of camber near the wing's centre of lift. In interspecific comparisons, energy absorpion and load to failure were greatest in Artibeus jamaicensis , the largest bat in our sample and the species with the highest wing loading, suggesting that wing loading may play a role in dictating the fuctional design of wing membranes.     

Dextran production by Leuconostoc mesenteroides in the presence of a dextranase producing yeast, Lipomyces starkeyi

Summary A new process for the production of small size dextran is developed in which dextran is produced by cultures of Leuconostoc mesenteroides in the presence of a partially constitutive mutant of Lipomyces starkeyi producing dextranase. Mixed cultures were examined by scanning electron microscopy with ruthenium to show the effects of the mixed culture on low molecular weight dextran (M.W. of 5,000 – 100,000) formation. The presence of the size variation in dextran was confirmed by gel permeation chromatography.     

Production of cyclodextrins using moderately heat-treated cornstarch

Cyclodextrins are very useful compounds for the food, cosmetic, pharmaceutic, and plastic industries. We developed a process for the production of cyclodextrins from moderately heat-treated cornstarch. This method had many merits. First, the cyclodextrins were not degraded by cyclodextrin glucanotransferase, because low molecular weight maltodextrins were hardly produced. Second, it was possible to remove the residual cornstarch by a simple method such as filtration or centrifugation. Third, the amount of cyclodextrin glucanotransferase used for cyclodextrin production was less than that using the traditional method. Fourth, the pretreating method was simple. And fifth, the residual starch could be used as substrate for the production of other compounds. Cyclodextrins were produced at optimum conditions: heating temperature was 65°C; heating time was 1 h; concentration of substrate was 7.5%; amount of enzyme loaded was 48 U g⁻¹ of substrate. Using these conditions, the results were as follows: the content of cyclodextrins, 50%; the conversion yield of substrate, 25%; the productivity per enzyme unit, 5.22 mg of cyclodextrins.