PubMed Health⌕ Search

Biomedical subjects

W Nagl

Publications and source records attributed to W Nagl.

18 recordsLinked to original sources
PubMed1992

Phytohemagglutinin gene expression during seed development of the runner bean, Phaseolus coccineus.

The expression of phytohemagglutinin (PHA) genes was studied in various tissues during the development of the seeds of Phaseolus coccineus cv. Hammond's Dwarf Scarlet by means of northern hybridization and reverse transcription polymerase chain reaction (RT-PCR). The expression is highly development-dependent, starting in the late stage (cotyledons begin to fill the endosperm cavity, i.e. 17 to 24 days after pollination), and tissue-specific. The highest levels of PHA-mRNA are found in the cotyledons (at a very late stage), much lower levels in the embryo axis. Very low levels could be detected in earlier stages of the endosperm, the integument, the funiculus, and probably also in the embryo suspensor. Some PHA mRNA was found in the cotyledons of dry seeds, indicating the presence of undegraded transcripts in mature seeds.

Base Sequence↗
PubMed1991

Immunocytochemical localization of the storage protein phaseolin in the embryo-suspensor of Phaseolus coccineus.

Antibodies against the bean storage protein, phaseolin, were induced in rabbits. Sections of bean embryos of various age were incubated with the antibodies, and exposed to fluorescein isocyanate (FITC) conjugated goat anti-rabbit immunoglobulin. Distinct positive signals were found in vacuoles of the suspensor giant cells. Immunofluorescent staining of protein bodies in cotyledon cells, histochemical staining reactions of the sections, as well as gel electrophoretic analysis of the proteins, isoelectric focusing and Western blotting confirmed the specificity and reliability of the immunochemical staining of the suspensor cells. The results give evidence for synthesis of storage proteins in the embryo-suspensor and indicate a function so far not detected of this embryonal nutritive organ.

Blotting, Western↗
PubMed1990

Polyploidy in differentiation and evolution.

Somatic and generative (germ-line) polyploidy are more widely spread phenomena among living organisms than generally thought. The occurrence of polyploidization and related events in normal and pathological differentiation, their recognized main functions, as well as the structural specificities of polyploid nuclei are reviewed, and the relationship between ontogenetic and phylogenetic events is discussed. The mechanisms leading to the polyploid state, as well as other processes resulting in a genomic condition different from the diploid one (such as DNA under-replication, gene amplification, and chromatin elimination), are briefly sketched. The various changes in chromosomal DNA described are, in conclusion, seen as evidence supporting the paradigm of a "fluid" or dynamic organization of the eukaryotic genome, as being part of a cybernetic feedback regulation system of gene expression. A model is proposed that unifies the aspects of DNA variation, chromatin structure, and diversification in ontogenesis and phylogenesis.

Animals↗
PubMed1988

Light-stimulated ultraweak photon reemission of human amnion cells and Wish cells.

Photon reemission in the ultraweak intensity range that is observed after irradiation of cell suspensions with light, reveals characteristic differences between normal human amnion cells and transformed Wish cells from the same parental tissue. The reemission kinetics, approximated best by a hyperbolical process, were studied as a function of cell density, showing that: malignant Wish cells have a photon storage capacity that is not improved by increasing the cell density; and that normal amnion cells exhibit a photon storage capacity that strongly increases with increasing cell density. The interpretation of this effect and the nature of the emitter are discussed.

Amnion↗
PubMed1985

Transcription of repetitive DNA in condensed plant chromatin.

Polyadenylated transcripts homologous to highly repetitive DNA were found in root tips of Vicia faba by Northern blot hybridization. Electron microscope autoradiography using [3H]uridine as a probe revealed transcription of condensed chromatin in various higher plants. This is consistent with the general rule that highly repetitive DNA is located within condensed chromatin, but it is new that this chromatin fraction is active in RNA synthesis to a considerable amount. Semi-quantitative comparison of the intensity of transcription in species with widely differing 2C DNA contents by means of light microscope autoradiography revealed an inverse relationship between the amount of 2C DNA (and condensed chromatin), and the rate of RNA synthesis.

Chromatin↗
PubMed1979

Transitory increase in chromosomal DNA (Fleulgen) during floral differentiation in Rhoeo discolor.

Scanning cytophotometric measurements on 3200 telophase and 1700 interphase nuclei (Feulgen-stained) in vegetative and reproductive buds of Rhoeo discolor revealed a transitory increase in staining intensity in more than half of the cells in early differentiating floral buds. The differences between the vegetative and floral nuclei are significant at the 0.001 level of probability and highly reproducible, independent of the type of hydrolysis used. We suggest that the different Feulgen extinction values reflect different nuclear DNA amounts, because methodical errors can fairly be excluded. The occurrence of an extra DNA (control DNA) of the kind of the floral DNA' detected by Wardell and Skoog (1973) and Wardell (1976) in tobacco is discussed.

Chromosomes↗
PubMed1978

Short duration of the mitotic and endomitotic cell cycle in the heterochromatin-rich monocot Allium carinatum.

Fraction labeled mitoses curves and caffeine-induced binucleate cell populations, respectively, were used to determine the duration of the mitotic and endomitotic cycle in roots of Allium carinatum, a leak with a 2C DNA content of 22.4 pg and a high proportion of heterochromatin. The mitotic cycle lasts, on an average, 8.1 h, the endomitotic one 7.5 h. These relatively short times (with respect to the nuclear DNA content) are discussed in the view of a possible role of heterochromatin in shortening cell cycle duration and possible advantage of the endomitotic cycle for rapid cell and tissue growth.

Caffeine↗
PubMed1978

Electron microscopic observations of a possible tubulin synthesis-polymerization complex in oocytes of a pond-skater.

Maturing oocytes of Gerris najas display, in ultrathin sections, protein fibrils extending from ribosomes, which are often arranged on ring-like cisternae of rough endoplasmic reticulum. In some cases, the fibrils apparently continue into typical microtubules. The possibility is discussed that the huge amount of microtubules of the egg cell is synthesized and polymerized in the form of specific ribosome-tubulin-filament-microtubule complexes.

Animals↗
PubMed1976

Effects of phytohormones on thermal denaturation profiles of Cymbidium DNA: indication of differential DNA replication.

Protocorm pieces of the orchid Cymbidium were aseptically cultured either without phytohormones, or with one of the growth promoting substances, auxin cytokinin, and gibberellin. The derivative melting profiles of the extracted DNA's differ from each other with respect to the size of various AT- and GC- rich fractions. Evidence has been obtained for the increase of the more AT--rich fractions in auxin-treated cultures, while gibberellin stimulated the expansion of the GC-rich fractions. These results are consistent with earlier cytological and cytochemical findings and indicate the involvement of hormone-controlled differential DNA replication in the development of Cymbidium protocorms in vitro.

Cells, Cultured↗
PubMed1976

Electron microscopic study of the differentiation and development of trophocytes and oocytes in Gerris najas (Heteroptera).

The differentiation of oogonia and oocytes, and of trophocytes, from undifferentiated germ line cells has been studied in Gerris najas, a pond skater, from the fourth instar to the adult animal. For the first time criteria have been obtained which allow the distinction between poorly differentiated early oogonia and nurse cells. The most important criteria are the size, shape, and structure of nuclei and mucleoli. This is consistent with the different function of these cell types, which is primarily a different nuclear function: meiosis in the oocytes, and RNA synthesis to support the trophic core and the oocytes in the trophocytes.

Animals↗
PubMed1975

An A + T-rich satelitte DNA in a monocotyledonous plant, Cymbidium.

The DNA of aseptically grown protocorms of a Cymbidium hybrid and in vitro developed leaves, as well as DNA of leaves and flower buds of Cymbidium ceres from the greenhouse, was analysed by analytical ultracentrifugation and thermal denaturation. Upon ultracentrifugation a satellite DNA with a buoyant density of 1.682 g/cm-3 appears as a shoulder on the main band (density 1.694 g/cm-3). Thermal denaturation reveals an inhomogeneous main peak with the major component melting at 84 degrees C and a separate peak melting at 75 degrees C. This is the first demonstration of a satellite DNA in a monocot, and one of the rare examples of a major A + T-rich DNA fraction in a plant.

Adenine↗
PubMedDate not supplied

Ribosome crystals in the oocyte of Gerris najas (Heteroptera).

Oocytes of the pond skater, Gerris najas, display ribosome tetramers that are arranged in the form of sheets in the vicinity of the nucleus. This is the first finding of ribosome crystals in an insect and suggests that ribosome crystallization may be a common phenomenon of cells that are inactive in protein synthesis.

Animals↗