Nucleolar Development Research Articles

Tritiated leucine incorporation in the developing hamster facial nucleus with injury: An autoradiographic study

Tritiated leucine incorporation was examined after axotomy of the hamster facial nerve in development in an attempt to correlate structural maturation of the nucleolus with levels of competence in the metabolic response to axon section. Changes in neuronal tritiated leucine incorportation were characterized by autoradiographic examination of the facial neuronal population after axotomy as specific stages in nucleolar development. The ability to increase incorporation over the normal as a result of injury in development coincided with the time of final nucleolar maturation, between 20 and 24 days postnatal age. Thus, there was a correlation between a specific morphologic event, the appearance of the adult nucleolar configuration, and the appearance of the mature protein metabolic response to injury of increased leucine incorporation.

Synaptosomal complexes and associated structures in microspread human spermatocytes.

Human spermatocytes processed with a modified microspreading technique which involves the use of sodium dodecyl-sulphate (SDS) have been used to construct synaptonemal complex (SC) karyotypes. Twenty two pachytene spermatocytes were selected for length quantitation. The mean values of relative lengths and centromeric indexes of each SC agree closely with values obtained by three-dimensional reconstructions (Holm and Rasmussen, 1977), except for SCs #4--5, 6--7 and 19--20. Absolute lengths are consistently longer in spreads (10.7% longer than in sections, on average). The mean total length of the SC complement is 258.7 micrometer. Six morphological types of XY pairs have been described. On the basis of the relationships between the XY pair, nucleolar development and autosome behavior, these six XY types are assumed to develop in succession. Type O XY pairs occur during late zygotene, types I and II XY pairs occur during early to mid-pachytene, and types III, IV and V occur during later pachytene substages. Alignment of the X and Y axes is observed at late zygotene, and formation of the SC occurs in relation with type I XY pairs. Progressive desynapsis occurs in types II and III. Splitting and fusion of the X and Y axes attain a maximum in types IV and V. The breakdown of the dense bodies associated with the X and Y axes occurs during stage V. --Bar-like structures, having a mean length of 2,100 A are associated with SCs in all the pachytene substages defined by the XY types. The average number of bars per nucleus is 46.2 (SD = 8.4, N = 20), and the average SC length per bar is 5.57 micrometer. The distribution along the SCs of 923 bars shows that near-termini locations are preferred (SC length per bar, 2.98 micrometer) and centromere regions are avoided (SC length per bar, 16.9 micrometer). --On the basis of these data, bars are similar to recombination nodules described in other organisms. The availability of a standard SC karyotype for microspreads and a temporal sequence given by the XY pair provide a basis for rapid screening of chromosome aberrations in human testicular biopsies.

Nucleolar ontogenesis in the uterine chick germ correlated with morphogenetic events

Nucleolar development in the cleaving chick germ up to the formation of the primary hypoblast was followed through a series of well-defined uterine and early incubated stages both by light and electron microscopy. Well-established criteria of nucleolar morphology were used for determining the developmental stage of onset of rRNA synthesis. By these criteria rRNA synthesis was first observed at midcleavage in uterine stage VII [1] germs. This could be correlated with the first morphogenetic event—the posterio-anteriorly orientated formation of the area pellucida which results in a bilaterally symmetrical blastoderm.

Semiautomatic morphometric analysis of the nucleolar development in the nucl. n. oculomotorii of Tupaia belangeri during ontogenesis.

The development during ontogenesis of the nuclear and nucleolar diameters and of the numbers of nucleoli per nucleus in the nucl. n. oculomotorii of 32 male Tupaia belangeri are described. The measurements of the nucleolar diameters were done automatically using the Micro-Videomat (Zeiss, Oberkochen). Increase of the nuclear and nucleolar diameters yielded a nearly sigmoid-shaped curve, which was fitted using the logistic growth function. The "ideal" value of the nucleolar diameter is 3.7 mum with a half value time of 22 days of ontogenesis and an enlargement factor of 1.53. The respective parameters for the nucleus are 12.2 mum, 28 days and 1.27. The ratio of the nuclear to nucleolar diameters decreases exponentially during ontogenesis to a value of 3.3. The validity of these easily determinable morphologic parameters for the RNA-synthesis is discussed. The number of nuclei with 2 or 3 nucleoli decreases during ontogenesis. The relevance of this fact for cell counting is also discussed.

Nucleolar development in the interphase of the cell cycle.

ABSTRACT Stereology of nucleoli at 3 different points of the cell cycle, in the middle of the G1 S and G2 of interphase, was accomplished in a naturally synchronous cell population rendered binucleate and thus ‘labelled’ and made identifiable by 1 h caffeine treatment in root meri-stems of Allium cepa L. Consistent structural changes were found so that nucleolar parameters by themselves can locate a cell at any interphase period. The growth of the nucleolus in the course of interphase takes place exclusively in its granular portion. The growth rate of this last component was found to be greater in the first half of interphase (5·4μm3h−1) than in the second (2·9 μm3 h”−1), as calculated for a nucleus with only one fused nucleolus. The changes in volume of the nucleolar components during interphase do not parallel the gene dosage. Nucleolar surface at each point seems to be the factor which determines the growth rate in the preceding interval, since these rates are inverted for fused and unfused nucleoli. The nucleolar volume occupied by lacunae is minimal in the S-period and shows an enormous increase by the middle of G2. We think our data may be the structural basis on which a model for nucleolar functioning in proliferating cells could be built.

Ribosomal RNA synthesis and the multiple, atypical nucleoli in cleaving embryos.

The rate of ribosomal RNA synthesis per nucleus in cleaving sea urchin embryos is similar to the rate at later embryonic stages. The multiple, atypical nucleoli, present in early embryos and usually attributed to decreased ribosomal RNA synthesis, are beginning stages of nucleolar formation. Full nucleolar development requires more time than the brief interphase of the rapidly dividing cells.

Response of cabbage root hairs to infection by Plasmodiophora brassicae

Cabbage root hairs provide a useful system for studying responses to infection by Plasmodiophora brassicae at the cellular level. Roots of cabbage seedlings grown in liquid culture were inoculated with zoospores of P. brassicae, and the effects of infection on host nucleolar development and root hair cell extension were studied. Within 18 h after the root hairs emerged from the trichoblasts the nucleoli of noninfected cells declined in diameter from 5 μ to less than 1 μ. Root hairs which became infected, whether 6 h old or 24 hold, had a nucleolar diameter ranging between 1.5 and 3 μ. The diameter of the nucleolus did not increase above 1.5–3 μ regardless of the age and number of Plasmodia within the cell. In addition to nucleolar enlargement, parasitized cells became stunted and often enlarged at their tips. Growth of Plasmodia within hair cells occurred with synchronous division of their nuclei. After penetration by the parasite there was an 18 h lag before the first nuclear division within the Plasmodia after which synchronous nuclear division occurred at about 4-h intervals.

Nucleolar and nissl substance development in nerve cells

Nucleolar and nissl substance development in nerve cells

The Macronucleus of Epistylis articulata From., during Conjugation: A Photometric Study

Previous article No AccessThe Macronucleus of Epistylis articulata From., during Conjugation: A Photometric StudyB. R. Seshachar, and C. M. S. DassB. R. Seshachar Search for more articles by this author , and C. M. S. Dass Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 27, Number 3Jul., 1954 Article DOIhttps://doi.org/10.1086/physzool.27.3.30152171 Views: 4Total views on this site Citations: 4Citations are reported from Crossref Journal History This article was published in Physiological Zoology (1928-1998), which is continued by Physiological and Biochemical Zoology (1999-present). PDF download Crossref reports the following articles citing this article:I.B. RAIKOV THE MACRONUCLEUS OF CILIATES, (Jan 1969): 1–128.https://doi.org/10.1016/B978-0-08-012339-4.50004-4J. Berech, W.J. Van Wagtendonk An autoradiographic study of the macronuclear changes occurring in Paramecium aurelia during autogamy, Experimental Cell Research 26, no.22 (Mar 1962): 360–372.https://doi.org/10.1016/0014-4827(62)90188-XMax Alfert, Norma O. Goldstein Cytochemical properties of nucleoproteins in Tetrahymena pyriformis; A difference in protein composition between macro-and micronuclei, Journal of Experimental Zoology 130, no.33 (Dec 1955): 403–421.https://doi.org/10.1002/jez.1401300303C.F. Ehret, E.L. Powers Macronuclear and nucleolar development in Paramecium bursaria, Experimental Cell Research 9, no.22 (Jan 1955): 241–257.https://doi.org/10.1016/0014-4827(55)90098-7

Nucleolar changes and development of nissl substance in the cerebral cortex of fetal guinea pigs

Nucleolar changes and development of nissl substance in the cerebral cortex of fetal guinea pigs