Floral development and expression of floral homeotic genes are influenced by cytokinins

Tobacco plants that are somatic mosaics for the expression of a cytokinin-synthesizing gene have viviparous leaves. Epiphyllous buds can be either vegetative or floral. Floral adventitious buds can be either normal or abnormal. Abnormalities of floral development correlate with: (i) a local activation of the cytokinin-synthesizing gene, (ii) a drastic increase in floral cytokinin content, and (iii) a decrease in the steady-state levels of mRNA homologues of the homeotic genes DEFA , GLO and PLENA of Antirrhinum majus . Thus, these data show in planta that cytokinins, a class of phytohormones, are able to alter the development of floral organs and to decrease the expression of three homeotic floral genes.     

Inflorescence-specific genes from Arabidopsis thaliana encoding glycine-rich proteins

Genomic and cDNA clones for three inflorescence-specific genes from Arabidopsis thaliana were isolated and characterized. The genes are tandemly organized in the genome on a 10 kb fragment. The expression of these genes is coordinately regulated in a developmental and organ-specific pattern. They are expressed predominantly in anthers at the later stage of flower development. The primary structure of the encoded gene products exhibits comparable features consisting of a hydrophobic domain at the N-terminal region followed by repeated glycine-rich motifs. Little homology is observed either between the glycine-rich domain of the three genes or with previously described glycine-rich proteins from other plant species.     

Intramolecular carboxylate catalysis in the depurination of a 7-methylguanosine derivative

We have compared the pH-independent rates of glycosidic hydrolysis in a carboxylate-bearing 7-methylguanosine derivative with those of a reference compound and with that of 7-methylguanosine itself. A syn-oriented carboxylate group affords catalysis in the hydrolysis reaction, although the instability of 7-alkylguanosines above pH 7 severely limits the useful pH range that could be studied. The effect of the carboxylate near neutral pH can be viewed in three different ways: it provides a 3-fold acceleration as compared to underivatized 7-methylguanosine, an approximately 30-fold acceleration when the decelerating effect of the ketal group is considered, and because of slow decomposition of the reference compound under the reaction conditions, we conclude that the carboxylate provides an acceleration of ≥43-fold as compared to the protio reference compound.     

Performance of a new family of modular,bed-supported,chromatography devices

Prepacked chromatography columns and cassette filtration units offer many advantages in bioprocessing. These include reduced labor costs and processing times, ease of storage, and enhanced process flexibility. Rectangular formats are particularly attractive as they can be easily stacked and multiplexed together for continuous processing. Cylindrical chromatography beds have dominated bioprocessing even though their bed support and pressure-flow performance vary with bed dimensions. This work presents the performance of novel, rhombohedral chromatography devices with internally supported beds. They are compatible with existing chromatography workstations and can be packed with any standard commercial resin. The devices offer pressure-flow characteristics independent of container-volume, simple multiplexing, and separation performance comparable to cylindrical columns. Their bi-planar, internal bed support allows mechanically less-rigid resins to be used at up to four times higher maximal linear velocities, and productivities approaching 200 g/L/h for affinity resins, compared to the 20 g/L/h typical of many column-based devices. Three 5 L devices should allow processing of up to 3 kg of monoclonal antibody per hour.     

PCR-mediated screening and labeling of DNA from clones

A simplified and economical protocol for DNA library screening and nonradioactive labeling is described. Bacterial clones are lysed in 1% of Triton X-100 and subjected to polymerase chain reaction in the presence of digoxigenin-11-dUTP to screen and simultaneously to label the DNA inserts. Bacteriallysates are stable in storage at −20°C and can be used repeatedly for PCR-mediated labeling. In this protocol, very low concentrations of dNTP, digoxigenin-dUTP, and primers are used in combination with a reduced reaction volume. This will considerably reduce the expense of screening and labeling bacterial clones and facilitate the exchange of DNA probes among laboratories.     

Synthesis and evaluation of the antidepressant activity of the enantiomers of bupropion

The synthesis of the enantiomers of bupropion, (rac)-2-tert-butylamino-3′-chloropropiophenone 1 (Wellbutrin®) is described. The enantiomers were compared with the racemate in both the tetrabenazine-induced sedation model and the inhibition of uptake of biogenic amine assay. No significant differences were found in their potencies to reverse tetrabenazine-induced sedation in mice or in their IC₅₀ values as inhibitors of biogenic amine uptake into nerve endings obtained from mouse brain. © 1993 Wiley-Liss, Inc.     

Experimentally induced colon cancer metastases in rat liver increase the proliferation rate and capacity for purine catabolism in liver cells

Metastases in rat liver were generated experimentally by intraportal injection of colon cancer cells to investigate the effects of cancerous growth on the metabolism of surrounding liver tissue. Maximum activities (capacity) of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, lactate dehydrogenase, succinate dehydrogenase, alkaline phosphatase, 5-nucleotidase, xanthine oxidoreductase, purine nucleoside phosphorylase and adenosine triphosphatase have been determined. Two types of metastases were found, a small type surrounded by stroma and a larger type in direct contact with hepatocytes. Both types affected the adjacent tissue in a similar way suggesting that the interactions were not mediated by stroma. High capacity of the degradation pathway of extracellular purines released from dead cells of either tumours or host tissue was found in stroma and sinusoidal cells. Metastases induced both an increase in the number of Kupffer cells and proliferation of hepatocytes. The distribution pattern in the liver lobulus of most enzymes investigated did not change distinctly. However, activity of alkaline phosphatase, succinate dehydrogenase and phosphogluconate dehydrogenase was increased in hepatocytes directly surrounding metastases. These data imply that the overall metabolic zonation in liver lobuli is not dramatically disturbed by the presence of cancer cells despite the fact that various metabolic processes in liver cells are affected.In honour of Prof. Dr. Z. Lojda for his 65th birthday     

Molecular characterization of the proteinase-encoding gene, prb1, related to mycoparasitism by Trichoderma harzianum

The soil fungus Trichoderma harzianum is a mycoparasitic fungus known for its use as a biocontrol agent of phytopathogenic fungi. Among other factors, Trichoderma produces a series of antibiotics and fungal cell wall-degrading enzymes. These enzymes are believed to play an important role in mycoparasitism. Among the hydrolytic enzymes, we have identified a basic proteinase (Prb1) which is induced by either autoclaved mycelia, fungal cell wall preparation or chitin; however, the induction does not occur in the presence of glucose. The proteinase was purified and biochemically characterized as a serine proteinase of 31 kDa and pl 9.2. Based on the sequence of three internal peptides, synthetic oligonudeotide probes were designed. These probes allowed subsequent isolation of a cDNA and its corresponding genomic clone. The deduced amino acid sequence indicates that the proteinase is synthesized as a pre-proenzyme and allows its classification as a serine proteinase. Northen analysis shows that the induction of this enzyme is due to an increase in the corresponding mRNA level.     

Growth kinetics of Rhizopus arrhizus in solid state fermentation of treated cassava

Summary Growth kinetics of Rhizopus arrhizus MUCL 28168 were determined for different treatments of cassava during solid state fermentation. The best case gave a specific growth rate () of 0.24 h^-1, a yield calculated on a basis that oxygen consumption (Y_x/o) was 2.9 g biomass. g^-1 O₂ consumed and the maintenance coefficient (m) was 0.004 g O₂ consumed. g^-1 biomass. h^-1.