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Biomedical subjects

A Spena

Publications and source records attributed to A Spena.

At least 19 recordsLinked to original sources
PubMed1992

Effect of thyroid hormones and their analogues on the mitochondrial calcium transport activity.

In this paper the authors studied the effects of thyroid hormones and their structural analogues on the mitochondrial calcium transport activities. The thyroid hormones, 3,5,3' L-triiodothyronine (LT3) and 3,5,3'5' L-tetraiodothyronine (LT4) at physiological intracellular concentrations between 7.2 and 9 nM, decouple total Ca++ transport, as well as inhibit the passive transport of Ca++, either due to oxidation of pyruvate, malate or succinate or after inhibition with rotenone. The optical isomers 3,5,3' D-triiodothyronine (DT3) and 3,5,3',5' D-tetraiodothyronine (DT4) are less effective at all the used concentrations. Furthermore the structural analogues 3,3',5' L-triiodothyronine (LrT3), 3,5-dicloro, 3',5' L-diiodothyronine (LDiClT2) and 3,5 L-diiodothyronine (LT2) furnished even less effects on the same activities. The effect of the thyroid hormones and of their structural analogues has revealed that the mitochondrial calcium transport may be influenced both by a stereospecific interaction between hormones and protein ligands and by a lipophilic chaotropic action on the mitochondrial membranes lipids. In this context it is interesting to consider that both thyroid hormones and Ca++ transport activity are interacting with the energetic metabolism by means of phosphorylation and substrate oxidation mechanism.

Animals↗
PubMed1991

The protein encoded by the rolB plant oncogene hydrolyses indole glucosides.

The rolB gene of Agrobacterium rhizogenes, whose expression stimulates the formation of roots by transformed plant tissues and other growth alterations in transgenic plants, codes for a beta-glucosidase able to hydrolyse indole-beta-glucosides. Indeed, we show that extracts of bacteria and/or plant tissue expressing the rolB protein hydrolyse indoxyl-beta-glucoside (plant indican). Because of the structural similarity between indoxyl-beta-glucoside and indole-3-acetyl-beta-glucoside (IAA-beta-glucoside), we propose that the physiological and developmental alterations in transgenic plants expressing the rolB gene could be the result of an increased intracellular auxin activity caused by the release of active auxins from inactive beta-glucosides. Thus two of the oncogenes carried by the T-DNA of the plant pathogen Agrobacterium rhizogenes (rolB and rolC) perturb plant growth and development by coding for beta-glucosidases with distinct specificities. Whereas the rolC beta-glucosidase releases cytokinins from their glucoside conjugates, the rolB encoded protein hydrolyses indole-beta-glucosides. The combined action of these two genes therefore is expected to modulate the intracellular concentration of two of the main growth factors active in plants.

Base Sequence↗
PubMed1991

The plant oncogene rolC is responsible for the release of cytokinins from glucoside conjugates.

The rolC gene of Agrobacterium rhizogenes, which drastically affects growth and development of transgenic plants, codes for a cytokinin-beta-glucosidase. Indeed, rolC protein expressed in Escherichia coli as a fusion protein hydrolyses cytokinin glucosides, thus liberating free cytokinins. Furthermore, beta-glucosidase activity present in E. coli extracts expressing the rolC protein was inhibited by affinity-purified antibodies specific for the rolC protein. Finally, rolC proteins expressed in transgenic plants were shown to be responsible for cytokinin-beta-glucosidase activity. Morphological and phytohormonal analysis, performed on transgenic plants that are somatic mosaics for the expression of the rolC gene, extend and confirm our interpretation that the developmental, physiological and morphological alterations caused by rolC expression in transgenic plants are primarily due to a modification of the cytokinin balance. These observations shed new light on the control of growth and differentiation in plants by growth factors.

Bacterial Proteins↗
PubMed1991

Cytosolic localization in transgenic plants of the rolC peptide from Agrobacterium rhizogenes.

The rolC gene of Agrobacterium rhizogenes codes for a peptide with an apparent molecular weight of approximately 20 kDa. Immunolocalization of the rolC peptide, in leaves of transgenic plants which are genetic mosaics for the expression of the rolC gene, is restricted to the phenotypically altered sectors. Subcellular fractionation of homogenates from 35S-rolC transgenic leaves shows the cytosolic localization of the rolC peptide.

Animals↗
PubMed1991

The indoleacetic acid-lysine synthetase gene of Pseudomonas syringae subsp. savastanoi induces developmental alterations in transgenic tobacco and potato plants.

The iaaL gene of Pseudomonas syringae subsp. savastanoi encodes an indoleacetic acid-lysine synthetase that conjugates lysine to indoleacetic acid. A chimaeric gene consisting of the iaaL coding region under the control of the 35S RNA promoter from cauliflower mosaic virus (35SiaaL) has been used to test if iaaL gene expression leads to morphological alterations in tobacco and potato. Transgenic tobacco plantlets bearing this construct have been shown to synthesize IAA-[14C]lysine when fed with [14C]lysine. In late stages of development, their leaves show an increased nastic curvature (epinasty) of the petiole and midvein, a finding suggestive of an abnormal auxin metabolism. The alteration is transmitted to progeny as a dominant Mendelian trait cosegregating with the kanamycin resistance marker. Transgenic potato plants harbouring the construct are also characterized by petiole epinasty. Moreover, 35SiaaL transgenic plants have an increased internode length in potato and decreased root growth in both tobacco and potato. An increased content of IAA-conjugates in leaf blade was found to correlate with the epinastic alterations caused by iaaL gene expression in tobacco leaves. These data provide evidence that IAA conjugation is able to modulate hormone action, suggesting that the widespread endogenous auxin-conjugating activities are of physiological importance.

Chromatography, High Pressure Liquid↗
PubMed1990

Unstable liaisons: the use of transposons in plant genetic engineering.

Transposable elements can be used to activate gene expression in clonal populations of cells and consequently to generate genetic mosaics. Plant mosaics, having organs composed of intermixed tissues with wild-type and mutant appearance, can be used to evaluate whether the action of a morphogenetic gene is cell-autonomous. Transposon-split gene constructions could also be used to raise plants transgenic for lethal genes and, in more general terms, they could be an ancillary tool in several types of biological experiment.

DNA Transposable Elements↗
PubMed1989

Cell-autonomous behavior of the rolC gene of Agrobacterium rhizogenes during leaf development: a visual assay for transposon excision in transgenic plants.

We describe a genetic switch based on the Ac transposable element of maize and the rolC gene of Agrobacterium rhizogenes, a dominant gene, which has pleiotropic effects on plant growth and morphology. Moreover, rolC gene expression under the control of the 35S cauliflower mosaic virus promoter decreases chlorophyll content in transgenic tobacco plants. Chlorophyll is a visible cell-autonomous marker, and it is shown here that the reduction in chlorophyll content caused by the rolC gene product allows us to monitor, in palisade or spongy mesophyll cells, Ac excision events resulting in rolC gene expression as pale-green sectors and spots. Our results indicate that the rolC gene product behaves in a cell-autonomous manner during leaf development, at least as far as chlorophyll accumulation is concerned. In addition, the rolC gene can be useful to evaluate visually if and when a transposable element is active. Most important, we propose the use of a transposable element as a tool to activate expression of morphogenetic genes in a clonal population of cells. This could be particularly useful when studying genes affecting growth and development whose constitutive expression can severely impair regeneration of transgenic plants.

Brassica↗
PubMed1989

Promoters of the rolA, B, and C genes of Agrobacterium rhizogenesare differentially regulated in transgenic plants.

Chimeric genes containing the beta-glucuronidase reporter gene under the control of the rolA, B, and C promoters of Agrobacterium rhizogenes are expressed in a regulated manner in transgenic plants. The intergenic region separating the rolB and C genes represents a bidirectional promoter. This bidirectional promoter regulates transcription for both genes in a similar fashion in aerial organs of the plants, but in a distinct way in roots. Moreover, both rolB and C promoter activities differ from those characteristic of the rolA promoter. Thus, promoters of bacterial origin show differential expression in transgenic plants, and regulation of roI gene expression plays a role in the biological effects caused by the rolA, B, and C genes.

Culture Techniques↗
PubMed1983

Two adjacent genomic zein sequences: structure, organization and tissue-specific restriction pattern.

A clone isolated from a library of genomic clones from Zea mays contains two adjacent zein light-chain genes. The nucleotide sequence of the two coding regions and their flanking sequences shows that the two genes represent two different subclasses of light-chain zeins. One belongs to an abundant and highly conserved class and the other, which is 88% homologous to the first, is less represented in the genome of maize line W64A. Both genes present in clone zE are anomalous: one contains a mutation that introduces a termination codon after 39 amino acids, the other has the ATG initiation codon mutated to CTG. The presence of inversions, insertions and short inverted or direct repeats in the flanking sequences suggests that zein genes may be subject to rearrangements and transpositions. Southern blot analysis of genomic DNA indicates that the particular arrangement represented by clone zE is present at least four times in maize line W64A but other arrangements are found in this and other maize lines. DNA extracted from different tissues and developmental stages is digested differently by enzymes sensitive to methylation of their target sequence. The results indicate that zein genes contain methylated sites that are demethylated in correlation with their expression.

Base Sequence↗
PubMed1983

[Echographic study of the inferior vena cava in abdominal neoplastic pathology. Comparison with the inferior cavography].

The authors evaluated the reliability of echography in the involvement of the inferior vena cava in the abdominal tumors. 137 patients were studied with echography and 125 with inferior cavography too. All the diagnosis were confirmed with arteriography and/or CT and/or surgical findings. The reliability of the echographic method was significant, and particularly in case of emboli and tumor invasion.

Abdominal Neoplasms↗
PubMed1982

[Ultrasound in the diagnosis of Wilms' tumor].

Ultrasound (US) play a very important role in the diagnosis of Wilms' tumour. The authors analyze the findings in 12 children affected by this neoplasia. The resolution power of 4 different diagnostic levels is also analyzed. They are: a) mass identification; b) diagnosis of the tumour nature; c) diffusion balance; d) recurrence control. The most relevant resolution power lies in the diagnosis of nature and in the recurrence control.

Child↗
PubMed1981

Coding capacity of complementary DNA strands.

A Fortran computer algorithm has been used to analyze the nucleotide sequence of several structural genes. The analysis performed on both coding and complementary DNA strands shows that whereas open reading frames shorter than 100 codons are randomly distributed on both DNA strands, open reading frames longer than 100 codons ("virtual genes") are significantly more frequent on the complementary DNA strand than on the coding one. These "virtual genes" were further investigated by looking at intron sequences, splicing points, signal sequences and by analyzing gene mutations. On the basis of this analysis coding and complementary DNA strands of several eukaryotic structural genes cannot be distinguished. In particular we suggest that the complementary DNA strand of the human epsilon-globin gene might indeed code for a protein.

Animals↗