Petunia plants escape from negative selection against a transgene by silencing the foreign DNA via methylation

Summary TransgenicPetunia hybrida clones harbouring the T-DNA gene2 ofAgrobacterium tumefaciens were used to test a strategy for the trapping of plant transposable elements. In thePetunia line used, floral variegation is due to the presence of the non-autonomous transposable elementdTph1 at theAn1 locus. The gene2 product converts the auxin precursor indole-3-acetamide and its analogue 1-naphthalene acetamide into the active auxins indole-3-acetic acid and 1-naphthalene acetic acid. Plant cells that express gene2 can use a low concentration of the precursors as auxins and become sensitive to the toxicity of high concentrations of these compounds. By selecting protoplast-derived microcalli or seedlings able to grow on medium with high precursor concentrations, variant plants were obtained in which gene2 was no longer expressed. Southern analysis, using gene2-specific probes, revealed that in one variant the T-DNA was deleted. For 30 other variants no alteration in gene2 structure was observed, indicating that transposable element insertion was not responsible for the inactivation of gene2. Analysis with restriction enzymes allowing discrimination between methylated or non-methylated DNA sequences showed that the inactivated gene2 sequences were methylated. Addition of the in vivo methylation inhibitor 5-azacytidine to the medium led to reactivation of gene2 expression in some of the variants. These observations demonstrated that reversible DNA methylation was the main cause of silencing of gene2 in this system.     

Monoclonal Antibodies Which Alter the Morphology of Cultured Chick Myogenic Cells

Two monoclonal antibodies that cause changes in the morphology of cultured myogenic cells are described. Antibody JG9 causes myoblasts to round up and causes myotubes to become thin, cable-like structures with multiple round swellings. Antibody JG22 causes both myoblasts and myotubes to become round refractile cells poorly attached to the substratum. The effects of both antibodies are reversible. Fab fragments of JG22 can cause the morphological change. A tentative identification of the antigen recognized by JG22 is made.     

NMR-based metabolomic study of type 1 diabetes

The genetic homogeneity of the people of Sardinia makes it an ideal place to study genetic related diseases such as type 1 diabetes, which in this island has one of the highest incidence worldwide. The principal objective of this study was to use ¹H high-resolution NMR spectroscopy and supervised methods of multivariate data analysis to highlight the importance of the variation of low concentration metabolites between healthy and diabetic Sardinian children. To achieve this goal, statistical analyses were performed after removal of the prevailing signals of sugars and citrate (related to carbohydrate metabolism) and of hippurate (a metabolite of bacterial origins) whose presence overwhelmed all the other compounds effects on classification. The variable influence in the statistical model showed that other metabolites deriving from gut microbial metabolism (p-cresol sulphate and phenylacetylglycine) were heavily involved in classification. This suggests the importance of changes in gut microbiota composition associated with type 1 diabetes in children.     

Fetal and postnatal development of cyclic GMP phosphodiesterase activity in the rat brain

Cyclic GMP concentration and cyclic GMP phosphodiesterase activity were studied in rat mothers and fetuses at 17, 19 and 21 days of intrauterine life and 0, 1, 4, 10, 15,20, 30 and 45 days after birth. During this developmental period, the increase in cyclic GMP concentration was discrete and the value in 15-day-old rats was already similar to the adult level. Cyclic GMP phosphodiesterase activity increased from 17- to 19-day fetuses and was significantly reduced in 21-day fetuses, neonates, and 1-day-old rats. This reduction may be a result of fetal endocrine preparation for parturition. During postnatal development, cyclic GMP phosphodiesterase activity increased in a parallel way in the limbic system, corpora striata, cerebral hemispheres, and diencephalon, reaching maximal level between 20 and 30 days after birth, and then decreasing to the adult value. The highest activity was found in corpora striata and the lowest in diencephalon. Cerebellar cyclic GMP phosphodiesterase activity was very high in the 4-day-old rat (257% of adult value) and diminished significantly in the 10-day-old rat with no subsequent changes. Kinetic analysis of the enzyme during postnatal forebrain development showed an increase in both the V_max and the apparent K_m. A decrease in the enzyme's V_max was observed only in the cerebellum.The importance of cyclic GMP phosphodiesterase regulation of cyclic GMP concentrations in the brain during development is discussed.     

Kurze Mitteilungen

Summary To the creamy-yellow colored bases of the rump feathers ofDucula bicolor adheres lipoid and noncolored powder. It is supposed, that the lipoid contains the creamy colour, which apparently is no carotenoid.