Purine salvage as metabolite and energy saving mechanism in Camelus dromedarius: the recovery of guanine

The preservation of purine ring as purine bases appears to be a common feature of camel liver. Hepatic guanine appears to be actively converted into GMP in the camel rather than further degraded. The limiting step of guanine degradation appears to be the lack of hepatic guanase activity. Higher purine bases over uric acid ratios were found in camel urine with respect to those of zebu.     

Isolation and characterisation of nuv11, a mutation affecting meiotic and mitotic recombination in Aspergillus nidulans

A mutant of Aspergillus nidulans, designated nuv11, has been isolated as hypersensitive to the monofunctional alkylating agent MNNG and the quasi-UV-mimetic mutagen 4-NQO. The mutation was recessive, resulting from mutation of a single gene which mapped to chromosome IV, and was non-allelic to the previously characterised repair-deficient mutations uvsB and uvsH which are also located on this linkage group. The nuv11 mutation results in slow growth, deficient intragenic and intergenic meiotic recombination, increased spontaneous chromosome instability, and increased intragenic and intergenic mitotic recombination in homozygous diploids. By screening a wild-type gene bank of A nidulans, a clone (pNUV11A40) has been isolated which complements the nuv11 mutation, restoring wild-type responses to both MNNG and 4-NQO.     

Glycoalkaloids of Solanum Series Megistacrolobum and related potato cultigens

Glycoalkaloids were used as evidence of the affinities of nine taxa of Solanum Series Megistacrolobum and related potato cultigens from western Bolivia. S. boliviense, S. sanctae-rosae and S. toralapanum contain the commertetraose sugar moiety and appear to represent a relatively wild group within the Series. S. megistacrolobum, S. sogarandinum and S. raphanifolium show anomolous glycoalkaloid profiles that probably reflect hybridization associated with human disturbance. Primitive forms of the S. χ ajanhuiri cultigen are indistinguishable chemicaliy from conspecific weeds that were previously classified as S. megistacrolobum. Variation in total glycoalkaloid content within Series Megistacrolobum likely reflects direct selection by humans for reduced glycoalkaloid levels during the domestication process.     

Biomedical implications from a morphoelastic continuum model for the simulation of contracture formation in skin grafts that cover excised burns

A continuum hypothesis-based model is developed for the simulation of the (long term) contraction of skin grafts that cover excised burns in order to obtain suggestions regarding the ideal length of splinting therapy and when to start with this therapy such that the therapy is effective optimally. Tissue is modeled as an isotropic, heterogeneous, morphoelastic solid. With respect to the constituents of the tissue, we selected the following constituents as primary model components: fibroblasts, myofibroblasts, collagen molecules, and a generic signaling molecule. Good agreement is demonstrated with respect to the evolution over time of the surface area of unmeshed skin grafts that cover excised burns between outcomes of computer simulations obtained in this study and scar assessment data gathered previously in a clinical study. Based on the simulation results, we suggest that the optimal point in time to start with splinting therapy is directly after placement of the skin graft on its recipient bed. Furthermore, we suggest that it is desirable to continue with splinting therapy until the concentration of the signaling molecules in the grafted area has become negligible such that the formation of contractures can be prevented. We conclude this study with a presentation of some alternative ideas on how to diminish the degree of contracture formation that are not based on a mechanical intervention, and a discussion about how the presented model can be adjusted.     

Monovalent and divalent cation permeation in acetylcholine receptor channels. Ion transport related to structure

Single channel patch-clamp techniques were used to study nicotinic acetylcholine receptors in cultured rat myotubes. The single channel conductance in pure cesium and sodium levels off at high concentrations, as if a binding site within the channel were saturating. The conductances at very low concentrations, however, are larger than predicted by the simplest one-site transport model fitted to the high-concentration data. At low concentrations, the current-voltage relations are inwardly rectifying, but they become more ohmic if a small amount of divalent cations is added externally. Magnesium and barium are good permeants that have rather high affinities for the channel. Upon adding low millimolar concentrations of these divalent cations externally to a membrane bathed in pure cesium, the inward current carried by cesium is decreased. As more divalent cations are added, the inward-going currents continued to decrease and the divalent cation replaces cesium as the main current carrier. The ion transport data are described by considering the size, shape, and possible net charge of the channel. In that way, even the complex features of transport are explained in a realistic physical framework. The results are consistent with the channel having long, wide, multiply occupied vestibules that serve as transition zones to the short, selective, singly occupied narrow region of the channel. A small amount of net negative charge within the pore could produce concentration-dependent potentials that provide a simple explanation for the more complicated aspects of the permeation properties.     

Maternal effects and generation mean analysis of seed-oil content in cotton (Gossypium hirsutum L.)

Summary The nature of gene action and of maternal influence governing cottonseed oil attributes were determined with four lines, two each with high and low seed-oil percentage. For this purpose, P1, P2, F0, F1, F2 and alternative sets of BC1 and BC2 generations were analysed in six cross-combinations and their reciprocals. Marginal extents of heterosis for seed-oil percentage were noticeable in F1, with inbreeding depression in F2. Data from reciprocal backcrosses provided evidence in favour of maternal rather than cytoplasmic effects of seed-oil development. Relatively higher extents of heterosis, sizeable inbreeding depression and reciprocally unequal F2 averages were characteristic of the seed index trait, which often showed a reversal of effects from F1 to F2. Reverse reciprocal backcrosses exhibited some differences, including greater resemblance between the types, (A/B)A and (B/A)A, in addition to variable dose effects in seed index. Thus, the differences between F1 seed index values were not due to cytoplasmic influence. Positive heterotic effects for seed-oil index, especially among the backcrosses, ranged between 16.08% and 47.29% over midparent averages. Genetic component estimates from analysis of similar sets of crosses differing only in reciprocal backcrosses, and also from sets of reciprocal crosses between any two parental combinations, were inconsistent. Scaling tests detected presence of epistasis within and between a majority of cross-combinations. Despite reciprocal differences, additive gene effects for seed-oil percentage were significant in 7 out of 24 crosses, representing high x low, low x high and low x low seed-oil parents. Those were, however, accompanied by significant dominance effects of higher order. In crosses involving low seed-oil percentage parents SA1060 and SA229, all six components were detected significant, with opposite effects of dominance and dominance x dominance epistatic components. Significant additive components were also detected for seed index and seed-oil index in 7 and 5 out of 24 crosses, respectively. In the inheritance of seed index and seed-oil index, dominance effects were more important. Epistatic components of additive x additive, and to a lesser extent, those of dominant x dominant were found significant.     

A practical test for in vitro evaluation of photosensitization: Assessment with hematoporphyrin derivative (HPD)

A simple procedure is described for the determination of the photosensitizing potency of drugs, using three leukemic cell lines, two of lymphocytic origin, L1210 and P388 and one of erythroid type, Friend-745. The procedure allows one to investigate several aspects of the photosensitization properties of tested compounds such as cellular localization and direct (trypan blue exclusion) or delayed (clonogenicity) photomediated toxicities.The method was assessed using crude hematoporphyrin derivative (HPD) as well as dihematoporphyrin ether (DHE) or commercially available Photofrin II. Results were compared to those obtained with normal cells, e.g spleen lymphocytes and erythropoietic stem cells (CFU-e), and discussed in the light of the relative response of normal versus transformed cells.Abbreviations DHE Dihematoporphyrin Ether - FCS Fetal Calf Serum - HPD Hematoporphyrin Derivative - PDT Photodynamic Therapy     

Contributions of algalization to rice growth,yield, N attributes and incidence of infestation with the blast fungusPyricularia oryzae under different fungicidal treatments

Inoculation of the Japonica rice, Giza 171, with blue-green algae along with 36 kg N/ha or complete N fertilization by 108 kg N/ha were tested along with blast-controlling fungicides: Kitazin-17, Fuji-one and Beam. The algal inoculum, which containedAnabaena cylindrica, Anabaena oryzae, Nostoc muscorum and Tolypothrix tenuis, was applled as 100 kg soil-based inoculum (90% moisture)/ha 5 days after transplanting. Plant growth, yield, N content and fertilizer-N-use efficiency were increased and the incidence and severity of leaf and neck intection withPyricularia oryzae were decreased by treatment with the fungicides applied with the algae along with 36 kg N/ha inslead of 108 kg N/ha without algae.

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Résumé On a testé l'inoculation du riz Japonica, Giza 171 avec l'algue bleu-verte, simultanément avec la fertillisation azotée soit à 36 kg N/ha solt complète à 108 kg N/ha et simultanément avec les fongicides Kitazin-17, Fuji-1 et Beam. L'inoculum d'algues, qui contenaltAnabaena cylindrica, Anabaena oryzae, Nostoc muscorum etTolypothrix tenuis, étalt appliqué à raison de 100 kg humides à 90% d'inoculum à base de sol par ha, 5 jours aprés la transplantation. La croissance des plantes, leur rendement, leur contenu azoté ainsi que l'efficience de la fertillisation azotée ont augmenté tandis que l'incidence et la sévérité de l'infection des feullies et du col parPyricularia oryzae ont décru par le traitement aux fongicides appliqué simultanément avec les algues et 36 kg N/ha par rapport au traitement à 108 kg N/ha sans algues.

     

Differential sensitivity to natural cell-mediated cytotoxicity of two rat colon adenocarcinoma variants differing in their tumorigenicity: identification of the effector cells as natural killer cells

Summary DHD/K12 TRb (PROb) and DHD/K12 TSb (REGb) are two cancer cell variants originating from the same rat colon adenocarcinoma. They differ in their tumorigenicity: when inoculated into syngeneic BDIX rats, PROb cells induce progressive tumors whereas REGb cells induce tumors which always regress. As previously described, there is an inverse relation between their tumorigenicity and their susceptibility to NCMC mediated by syngeneic spleen or peripheral blood lymphocytes: PROb cells are significantly less sensitive to NCMC than REGb cells. This suggests a role for NCMC in the regression of REGb tumors. In this work the BDIX NCMC effector cells active in vitro against REGb cells were identified as NK cells according to four criteria: (1) efficacy in a 4-h ⁵¹Cr release assay, (2) sensitivity to anti-asGM1 antibody plus complement, (3) LGL morphology, and (4) ability to bind with the same affinity REGb and YAC-1 cells. In spleen, these NK cells were heterogeneous with respect to their asGM1 surface density and their morphology. PROb cells were not lysed by these NK cells in a short-term cytotoxicity assay, but only in a 16-h assay. It was shown that PROb and REGb cells were bound with the same affinity by NK cells, thus they certainly differ in their ability to resist to NK lytic mechanisms. This difference could play a role in the different tumorigenicity of the two variants. Abbreviations used: NK, natural killer; NC, natural cytotoxic; NCMC, natural cell-mediated cytotoxicity; asGM1, asialo GM1; LL, large lymphocytes; LGL, large grnular lymphocytes; LAL, large agranular lymphocytes; PBMNC, peripheral blood mononuclear cells; E:T, effector to target cell ratio; C:H, cold to hot cell ratio; FBS, fetal bovine serum