The role of ethylene and reducing agents on anther culture response of tetraploid potato (Solanum tuberosum L.)

Summary The role of ethylene in embryogenesis of cultured potato anthers was studied indirectly by testing various substances known to affect ethylene formation. The reducing agents ascorbic acid and L-cysteine prevented browning of anther cultures and significantly stimulated embryogenesis. Embryogenesis was also promoted by the use of the ethylene inhibitors AgNO₃ and n-propyl-gallate and by the polyamines spermidine and putrescine. The use of the ethylene releasing compound ethrel significantly inhibited embryogenesis.Abbreviations MS Murashige & Skoog - PVP polyvinylpyrrolidone - MW molecular weight - ACC 1-aminocyclopropane-1-carboxylic acid - ethrel 2-chloroethylphosphonic acid (ethephon)     

Haematological cell proliferation and differentiation responses to perturbations of polyamine biosynthesis

Combined administration of methylglyoxal-bis-guanylhydrazone (MGBG) (25 mg/kg) with difluoromethylornithine (DFMO), or MGBG alone at a higher dose (50 mg/kg), to mice resulted in a decreased white cell count (WBC) in the peripheral blood while DFMO or MGBG alone at a lower dose (25 mg/kg) had no effect. As expected, DFMO alone increased the number of colony forming units spleen (CFU-s), colony forming units diffusion chamber granulocyte (CFU-dg) and colony forming units culture (CFU-c) in the bone marrow. MGBG treatment led to an increase in CFU-dg alone. Combined treatment seemingly had no effect on marrow stem cells. Total tibial and differential counts were not affected by any of the treatments. Cell proliferation in diffusion chamber cultures, as judged by CFU-dg colony formation, was impaired by MGBG alone or in combination with DFMO, at dose levels which had no effect or increased the precursor cell number in the bone marrow. This effect was partially reversed with either putrescine or spermidine. Determination of intracellular polyamine concentrations, demonstrated decreased putrescine and spermidine levels after DFMO administration. As expected, MGBG treatment resulted in decreased spermidine and spermine levels, concomitant with an increase in putrescine. In mice which received both agents, rather than only MGBG, after 3 days higher intracellular polyamine concentrations were observed. After 11 days, however, there was no significant difference between the two groups.     

HEMOPOIETIC STEM CELL PROLIFERATION AND MIGRATION FOLLOWING BORDETELLA PERTUSSIS VACCINE

The ability of a single injection of killed, intact bacteria to effect an increase in the proliferative rate of hemopoietic stem cells was studied. The total numbers of colony forming units in bone marrow, spleen and peripheral blood as well as the proportion of CFU in cycle was assessed. Splenic CFU were observed to rise exponentially due initially to in situ proliferation and later to proliferation in bone marrow with migration via the blood to the spleen. The results are discussed in the light of current concepts of stem cell regulation.     

High frequency one-step gene replacement in Trichoderma reesei. I. Endoglucanase I overproduction

The chromosomal cellobiohydrolase 1 locus (cbh1) of the biotechnologically important filamentous fungus Trichoderma reesei was replaced in a single-step procedure by an expression cassette containing an endoglucanase I cDNA (egl1) under control of the cbh1 promoter. CBHI protein was missing from 37–63% of the transformants, showing that targeting of the linear expression cassette to the cbh1 locus was efficient. Studies of expression of the intact cbh1-egl1 cassette at the cbh1 locus revealed that egl1 cDNA is expressed from the cbh1 promoter as efficiently as cbh1 itself. Furthermore, a strain carrying two copies of the cbh1-egl1 expression cassette produced twice as much EG I as the amount of CBHI, the major cellulase protein, produced by the host strain. The level of egl1-specific mRNA in the single-copy transformant was about 10-fold higher than that found in the non transformed host strain, indicating that the cbh1 promoter is about 10 times stronger than the egl1 promoter. The 10-fold increase in the secreted EG I protein, measured with an enzyme-linked immunosorbent assay (ELISA), correlated well with the increase in egl1-specific mRNA.     

Immunological characterization of lysyl hydroxylase, an enzyme of collagen synthesis

Antibodies to pure lysyl hydroxylase from whole chick embryos were prepared in rabbits and used for immunological characterization of this enzyme of collagen biosynthesis. In double immunodiffusion a single precipitation line was seen between the antiserum and crude or pure chick-embryo lysyl hydroxylase. The antiserum effectively inhibited chick-embryo lysyl hydroxylase activity, whether measured with the biologically prepared protocollagen substrate or a synthetic peptide consisting of only 12 amino acids. This suggests that the antigenic determinant was located near the active site of the enzyme molecule. Essentially identical amounts of the antiserum were required for 40% inhibition of the same amount of lysyl hydroxylase activity units from different chick-embryo tissues synthesizing various genetically distinct collagen types. In double immunodiffusion a single precipitation line of complete identity was found between the antiserum and the purified enzyme from whole chick embryos and the crude enzymes from chick-embryo tendon, cartilage and kidneys. These results do not support the hypothesis that lysyl hydroxylase has collagen-type-specific or tissue-specific isoenzymes with markedly different specific activities or immunological properties. The antibodies to chick-embryo lysyl hydroxylase showed a considerable degree of species specificity when examined either by activity-inhibition assay or by double immuno-diffusion. Nevertheless, a distinct, although weak, cross-reactivity was found between the chick-embryo enzyme and those from all mammalian tissues tested. The antiserum showed no cross-reactivity against prolyl 3-hydroxylase, hydroxylysyl galactosyl-transferase or galactosylhydroxylysyl glucosyltransferase in activity-inhibition assays, whereas a distinct cross-reactivity was found against prolyl 4-hydroxylase. Furthermore, antiserum to pure prolyl 4-hydroxylase inhibited lysyl hydroxylase activity. These findings suggest that there are structural similarities between these two enzymes, possibly close to or at their active sites.     

Growth of mouse and human bone marrow in diffusion chambers in mice. Development of myeloid and erythroid colonies and proliferation of myeloid stem cells in cyclophosphamide- and erythropoietin-treated mice.

Both murine and human bone marrow cells were cultured in plasma clots which were formed inside diffusion chambers implanted into cyclophosphamide- and saline-treated mice. After an initial fall, the number of mouse bone marrow cells and numbers of mouse myeloid stem cells (CFU-C) and agar cluster-forming units rose faster in the cyclophosphamide-treated animals. These hosts also favored formation of myeloid (CFU-D-G) and erythroid (CFR-D-E) colonies and myeloid higher than those of CFU-C from the same marrow population. These observations suggest the existence of humoral factors stimulating granulocyte progenitor cell replication and differentiation. At its best the increment of CFU-D-E number was equivalent to that caused by a single 0.1 unit erythropoietin dose. Culture of normal human marrow cells resulted in colonies in the plasma clot containing only granulocytes and macrophages. Cyclophosphamide-treated host animals were essential for human CFU-D-G development. Plating efficiency for human marrow myeloid colonies was better in the conventional in vitro agar cultures than in diffusion chambers.     

A genome‐wide linkage map for the house sparrow (Passer domesticus) provides insights into the evolutionary history of the avian genome

The house sparrow is an important model species for studying physiological, ecological and evolutionary processes in wild populations. Here, we present a medium density, genome wide linkage map for house sparrow (Passer domesticus) that has aided the assembly of the house sparrow reference genome, and that will provide an important resource for ongoing mapping of genes controlling important traits in the ecology and evolution of this species. Using a custom house sparrow 10 K iSelect Illumina SNP chip we have assigned 6,498 SNPs to 29 autosomal linkage groups, based on a mean of 430 informative meioses per SNP. The map was constructed by combining the information from linkage with that of the physical position of SNPs within scaffold sequences in an iterative process. Averaged between the sexes; the linkage map had a total length of 2,004 cM, with a longer map for females (2,240 cM) than males (1,801 cM). Additionally, recombination rates also varied along the chromosomes. Comparison of the linkage map to the reference genomes of zebra finch, collared flycatcher and chicken, showed a chromosome fusion of the two avian chromosomes 8 and 4A in house sparrow. Lastly, information from the linkage map was utilized to conduct analysis of linkage disequilibrium (LD) in eight populations with different effective population sizes (N_e) in order to quantify the background level LD. Together, these results aid the design of future association studies, facilitate the development of new genomic tools and support the body of research that describes the evolution of the avian genome.     

Bacterial Viability and Physical Properties of Antibacterially Modified Experimental Dental Resin Composites

Purpose

To investigate the antibacterial effect and the effect on the material properties of a novel delivery system with Irgasan as active agent and methacrylated polymerizable Irgasan when added to experimental dental resin composites.

Materials and Methods

A delivery system based on novel polymeric hollow beads, loaded with Irgasan and methacrylated polymerizable Irgasan as active agents were used to manufacture three commonly formulated experimental resin composites. The non-modified resin was used as standard (ST). Material A contained the delivery system providing 4 % (m/m) Irgasan, material B contained 4 % (m/m) methacrylated Irgasan and material C 8 % (m/m) methacrylated Irgasan. Flexural strength (FS), flexural modulus (FM), water sorption (WS), solubility (SL), surface roughness R_a, polymerization shrinkage, contact angle Θ, total surface free energy γ_S and its apolar γ_S ^LW, polar γ_S ^AB, Lewis acid γ_S ⁺and base γ_S ^- term as well as bacterial viability were determined. Significance was p < 0.05.

Results

The materials A to C were not unacceptably influenced by the modifications and achieved the minimum values for FS, WS and SL as requested by EN ISO 4049 and did not differ from ST what was also found for R_a. Only A had lower FM than ST. Θ of A and C was higher and γ_S ^AB of A and B was lower than of ST. Materials A to C had higher γ_S ⁺ than ST. The antibacterial effect of materials A to C was significantly increased when compared with ST meaning that significantly less vital cells were found.

Conclusion

Dental resin composites with small quantities of a novel antibacterially doped delivery system or with an antibacterial monomer provided acceptable physical properties and good antibacterial effectiveness. The sorption material being part of the delivery system can be used as a vehicle for any other active agent.