Biomedical subjects

L F La Cour

Publications and source records attributed to L F La Cour.

10 recordsLinked to original sources

PubMed1978

The constitutive heterochromatin in chromosomes of Fritillaria Sp., as revealed by Giemsa banding.

The incidence of C-bands (constitutive heterochromatin), as determined by differential Giemsa staining, was studied in the chromosomes of 56 species, varietal forms and subgenera of Fritillaria and 30 of them are illustrated. With the exception of the subgenera Korolkowi, a supposed link between lilies and fritillaries, and chromsome complements of all plants contained bands. There were wide differences in the size and number of these bands among species both within and between groups. In those with the largest and most abundant bands, there was a pronounced tendency for centromeric localization, both in Old and New World species. The Giemsa positive centromeres were masked when this occurred. Heteromorphy in respect of banding occurred in most species. The relation of repetitive DNA sequences with heterochromatin is discussed, as is also the problem of evolution in Fritillaria.

Azure Stains↗

PubMed1977

Some morphological aspects of the synaptonemal complex in higher plants.

The synaptonemal complex is illustrated in electron micrographs from pollen mother cells (p.m.cs) of the following plants: Fritillaria lanceolata, Allium fistulosum, Tulbaghia violacea, Luzula purpurea, Phaedranassa viridiflora and the tulip cultivar Keiserkroon. The possibility that the lateral elements in synaptonemal complexes of plants are tubiform structures is discussed in relation to their fine structure and in the light of a deformity seen in them. An assessment of the evidence suggesting that both lateral and central elements in the complex are ribonucleoprotein structures is made. The effect of brief water treatment on the chromatin and synaptonemal complex at zygotene in p.m.cs of the Phaedranassa is discussed, particularly with reference to two precisely oriented axial strands then seen running between the lateral elements. Examination of stages of premeiotic interphase and early leptotene in p.m.cs of the Fritillaria, revealed that the axial cores laid down at leptotene are formed first in heterochromatic regions, which in this species are locked in chromocentres that persist until pachytene. Further, at leptotene the chromatin in these parts was singularly more decondensed (diffuse) than at any other period, including the premeiotic interphase, subsequent stages of meiosis and mitotic cycle in meristems. It is suggested that the diffuse state of the chromatin in chromocentres at the onset of leptotene, allows the necessary freedom of movement required to promote homologous pairing of the heterochromatic segments. Evidence of such a movement was indicated by a change in position of the nucleoli, which moved from a more central position at early premeiotic interphase to a peripheral one at the onset of leptotene, when they are seen adpressed to the nuclear envelope.

Cell Nucleus↗

PubMed1975