Structure and expression of a gene from Arabidopsis thaliana encoding a protein related to SNF1 protein kinase

The AKin10 gene from Arabidopsis thaliana encoding a putative Ser/Thr protein kinase (PK) has been isolated and characterized. The AKin10-encoding gene is located on a genomic 5.4-kb BamHI fragment and contains ten introns, one being located in the 5' untranslated region. The deduced amino acid sequence of AKin10 is 65% identical over the catalytic domain to the yeast PK (SNF1). SNF1 is essential for the derepression of many glucose-repressible genes, including Suc2 which encodes invertase. Southern blot hybridization experiments suggested the presence of one copy of the gene per haploid genome of A. thaliana. Northern hybridization experiments indicated that this gene is expressed in roots, shoots and leaves. AKin10 may play an important role in a signal transduction cascade regulating gene expression and carbohydrate metabolism in higher plants.     

Effect of alpha-adrenoreceptors in the control of spontaneous motility and morphine withdrawal syndrome.

The effects of different alpha-2 agonists on the spontaneous motility in naive and morphine tolerant mice were studied. Clonidine caused a reduction at the lower (1-3 micrograms Kg-1 i.p.) and higher (100 micrograms Kg-1 i.p.) doses and no effect at 10-30 micrograms Kg-1 i.p. in naive mice, while an increase was found at the intermediate doses (10-30 micrograms Kg-1 i.p.) in morphine tolerant mice. The clonidine-induced inhibition on spontaneous motility at the lower and higher doses was prevented both in naive and tolerant mice by idazoxan pretreatment. In morphine-treated animals the increase induced by clonidine was antagonized by prazosin. The action of guanabenz and guanfacine on locomotion differed from clonidine, by producing inhibition only at higher doses (100-300 micrograms Kg-1 i.p.). Clonidine, but not guanfacine or guanabenz, prevented the withdrawal syndrome precipitated by naloxone. Thus the only alpha-2 agonistic properties do not appear sufficient to explain the prevention of morphine abstinence by clonidine in mice, which can represent a single model to screen anti-withdrawal drugs.     

Mouse Chromosome 7

Chair of Committee for Mouse Chromosome 7     

Genetic analysis of blood pressure in the Milan hypertensive strain of rat (Rattus norvegicus)

Estimates of heritability (h2) of blood pressure level and the number of loci controlling the trait were derived from two genetic crosses involving the Milan hypertensive strain of rat and its control with normal blood pressure. In the genetic cross involving backcrosses, the estimates were h2 = 64% and the number of loci was two or three; there was some evidence of dominance of the alleles for normal blood pressures. In the other cross with only F2's, the degree of genetic determination (heritability in the broad sense) was 45%, involving at least three loci.     

Chromosomal damage induced in human lymphocytes by low doses of D-T neutrons

Unstable chromosome aberrations induced by in vitro irradiation with zero plus seven low doses of 14.8 MeV D-T neutrons in the range 3.55-244 mGy have been analysed in human peripheral blood lymphocytes. In order to obtain the required large numbers of scored cells for such low doses, fourteen laboratories participated in the experiment. The dose responses for dicentrics, excess acentrics and total aberrations, fitted well to the Y = alpha D model. The alpha coefficient of yield for dicentrics, 1.60 +/- 0.07 X 10(-2) Gy-1, compares well with the values obtained in previous studies with D-T neutrons at somewhat higher doses. Results from a previous collaborative study using 250 kVp X-rays over a comparable dose range indicated the possible existence of a threshold below 50 mGy. In the present study there is no clear evidence for neutrons for such a threshold. However, the data were insufficient to permit the rejection of a possible threshold below approximately 10 mGy.     

Effects of nitrilotriacetic acid on the induction of gene mutations and sister-chromatid exchanges by insoluble chromium compounds

The influence of nitrilotriacetic acid trisodium salt (NTA) on the mutagenic and clastogenic activity of several water-insoluble or poorly soluble chromium compounds was determined by means of the Salmonella/microsome assay (plate test on TA100 strain) and the sister-chromatid exchange (SCE) test in mammalian cell cultures (CHO line). NTA in itself did not induce gene mutations nor did it increase the frequency of SCE. Cr(VI) compounds (Pb, Ba, Zn, Sr and Ca chromates) and an industrial Cr(VI) pigment, chromium orange (containing PbCrO4 PbO), were inactive or scarcely active mutagens in the Salmonella/microsome test when dissolved in water, but they were increasingly mutagenic when solubilized by 0.5 N NaOH or NTA (10 or 100 mg/ml). Also, the mutagenic activity of Cr(VI), contaminating an industrial Cr(III) pigment (chromite), was slightly enhanced by NTA. Mutagenicity of chromates was correlated with the amounts of Cr(VI) solubilized by NTA or alkali, as determined by the colorimetric reaction with diphenylcarbazide and atomic absorption spectrophotometry, and was decreased by incubation with microsomes, due to reduction of Cr(VI) to the genetically inactive Cr(III) form. In the SCE assay, the insoluble or poorly soluble Ba, Zn, Sr and Ca chromates and the insoluble Cr(VI) pigments zinc yellow (containing ZnCrO4 Zn(OH2], chromium yellow and molybdenum orange (both containing PbCrO4) were directly clastogenic due to cellular endocytosis taking place in prolonged treatments, and NTA significantly increased their chromosome-damaging activity.     

Stereology in the extraction of information from images

Some important aspects for information extraction by stereology from images in surgical and experimental pathology are discussed. The relationship between stereology and morphometry is briefly discussed, with the most important conditions for stereologic analysis in pathology pointed out. The possibilities, limits and problems inherent in stereologic and morphometric analysis in pathology are explained in two examples: so-called "small airways disease" and tight junctions of hepatocytes during physiologic choleresis.     

Influence of 2'-deoxyguanosine upon the development of DTH effector T cells and suppressor T cells in vivo

Subcutaneous (s.c.) immunization of mice with allogeneic spleen cells can induce delayed-type hypersensitivity (DTH) to both major and minor histocompatibility antigens. Intravenous immunization with allogeneic spleen cells, however, induces a poor state of DTH. Furthermore, i.v. immunization with allogeneic spleen cells, especially if they have been irradiated, induces suppressor T lymphocytes. These suppressor T cells are capable of suppressing the host-vs-graft (HvG) DTH reactivity that normally arises after s.c. immunization. Moreover, they can suppress the development of anti-host DTH effector T cells during graft-vs-host (GvH) reactions. These models for HvG and GvH DTH reactivity were used to study the influence of 2'-deoxyguanosine (dGuo) and guanosine (Guo) on the generation of DTH-reactive T cells and suppressor T cells in vivo. It was found that daily i.p. administration of 0.01 mg dGuo to mice immunized i.v. partially prevented the generation of suppressor T cell activity, whereas daily administration of 0.1 or 1 mg dGuo resulted in a complete abolition. Administration of dGuo has no effect on the anti-host DTH reactivity by spleen cells from nonsuppressed donors except for when a daily dose of 10 mg is administered. This dose proved to be toxic for precursors of DTH effector T cells. Daily i.p. injection of Guo had no effect on the generation of suppressor T cells nor on the generation of DTH effector T cells. The effect of dGuo was found to be due to a direct effect on suppressor T cells and not to the induction of contrasuppressor cells. These data suggest a differential sensitivity of DTH-reactive T cells and suppressor T cells for dGuo. Because suppressor T cells and DTH-reactive T cells require proliferation for expressing maximal functional activity in the systems used, both cell types probably have different enzyme activities involved in the purine metabolism and similar deoxycytidine kinase activities, but have different nucleotidase (5'NT) activities, those in suppressor T cells being the lowest. If so, suppressor T cells will accumulate deoxyguanosine triphosphate, which causes an inhibition of the ribonucleotide reductase activity and thus of the DNA synthesis by these cells.     

Evolution of the genome size inAkodon (Rodentia,Cricetidae)

Nuclear DNA contents were estimated by microdensitometry in five species of Akodon rodents: Arodon molinae, A. dolores, A. mollis, A. azarae, Bolomys obscurus) and in three chromosomal varieties of A. molinae (2n = 42; 2n = 43, 2n = 22). The data obtained showed that the species with the highest DNA content was B. obscurus, followed in order of decreasing genome size by A. molinae, A. mollis, A. dolores and A. azarae. In A. molinae the forms with 2n = 42 chromosomes had the lowest and the forms with 2n = 44 the highest amount of DNA, while the forms with 2n = 43 had intermediate DNA contents. The variation in DNA amount detected in A. molinae was interpreted as a phenomenon of amplification occurring in the chromosomal areas involved in the chromosomal rearrangement giving rise to the polymorphism exhibited by this species. The DNA contents of shared chromosomes (chromosomes with similar size, morphology and G banding pattern, which are found in two or more phylogenetically related species), were compared and correlated with values of total nuclear DNA. The information obtained indicates that: (a) shared chromosomes have variable amounts of DNA: (b) in a given species there is a correlation between the amount of nuclear and chromosomal DNA in most shared chromosomes (and perhaps in most of the chromosomal complement), e.g., the higher the amount of nuclear DNA, the higher the content of DNA in shared chromosomes; (c) some chromosomes may undergo processes of amplification or deletion restricted to certain regions and usually related with mechanisms of chromosomal rearrangements.(ABSTRACT TRUNCATED AT 250 WORDS)