Nukleoluszahl und -gr��e w�hrend des Zellzyklus

Sequential estimation of nuclear DNA and silver staining of nucleoli in plant cells

A method for sequential estimation of nuclear DNA and silver staining of nucleoli in plant cells is described. Feulgen staining is done first and nuclear DNA estimated by absorption cytophotometry. Following this, the slides are stained with AgNO3. The method has been used to study the process of nucleolar fusion in garlic (Allium sativum L.) meristem root tip cells. It was found that during interphase nucleoli rarely fused, thus most fusion must have occurred before the G1 phase of the cell cycle.

Changes in nucleolar structure, number and size in cellular activation and inactivation. Observations in human phytohaemagglutinin-treated lymphocytes

Lymphocytes in human peripheral blood are small, relatively inactive cells. The addition of phytohaemagglutinin (PHA) to cultures of these cells causes a marked increase in cellular and nuclear size, DNA-synthesis and metabolic activity, which reaches a maximum three days after the onset of culturing. The cells then undergo an inactivation process over a period of approximately ten days by which time they have reverted to cells resembling small, inactive lymphocytes. Within the first three days, nucleoli increase in size and number, changing from ring-shaped to nucleolonema-exhibiting to compact nucleoli. In the course of the inactivation process the nucleoli decrease in size and change from compact nucleoli directly into ring-shaped nucleoli. Thus activation and inactivation pathways are different. There is an increase in the number of nucleoli during the inactivation phase up to the seventh day in culture, followed by a slight decrease until day 14. This suggests that nucleoli in metabolically active cells have a tendency to fuse, whereas those in inactive cells tend to fragment.

Quantitative morphological studies of neuropathological changes. Part 1

Quantitation of morphological changes in the nervous system is valuable for demonstrating different regions and cell types involved in a pathological process. Quantitative anatomical studies are numerous, whereas quantitations of pathological conditions are relatively few. This seems to be due partly to technical difficulties arising when comparing normal with pathological brain tissue. Shrinkage of the whole brain or of substructures is important but difficult to determine, and earlier studies are often inaccurate due to lack of precise measurement of this parameter. This review deals with three different technical aspects: (1) measurements at the macroscopical level, (2) the light microscopical morphometry, and (3) the stereological principles which are used primarily in electron microscopical quantitation. The most used techniques and formulas are reviewed in order to give an impression of the possibilities and requirements in quantitative neuropathology. After each of the major areas, macroscopical measurements, determination of nuclear and cell size and nuclear number, vascular network, and stereology, a few practical comments are given as well as references for further information on the topic. The quickly developing electronic image analysis is dealt with in the section on capillary network measurements and in the last, concluding section.

The influence of the cell cycle on structure and number of nucleoli in cultured human lymphocytes

The nucleoli of lymphocytes undergo a typical sequence of structural changes after stimulation by phytohaemagglutinin. These changes are independent of the cell cycle. Neither the inhibition of DNA-synthesis (by adenosine and methotrexate), nor the elimination of postmitotic interphase nuclei (by a colchicine block of mitoses), nor the release from such blocks has a noticeable effect on nucleolar structure or on the sequence of nucleolar changes. The number of nucleoli per cell is clearly influenced by the cell cycle. Mitosis leads to a marked increase in the number of nucleoli, whereas in all stages of interphase a decrease occurs.

Satellite association frequency and number of nucleoli depend on cell cycle duration and NOR-activity. Studies on first, second, and third mitoses of lymphocyte cultures

In human lymphocyte cultures the frequencies of satellite associations in first, second, and third mitoses were investigated using the BUDR-method. A marked decrease of the association frequency with increasing numbers of cell cycles was found. The number of nucleoli seen in interphase is correlated with the satellite association frequency in the respective metaphase. Satellite association is positively correlated to Ag-staining intensity of the NORs. Individual differences in satellite association are due to differences in NOR activity and in lymphocyte activation. BUDR diminishes somewhat the Ag-staining intensity of the NORs but has no effect on satellite association frequencies. The main reason for the decrease of satellite association frequency in second and third lymphocyte mitoses is presumably a certain dislocation of the original chromosome position during mitosis and a decreased possibility of association during the short interphases. The high association frequency in first mitosis resembles the chromosome position in the long interphase of G0-lymphocytes.

Nucleoli of cultured human lymphocytes. II. Nuceolar fusion and its relation to acrocentric association

Nucleolar fusion and nucleolus formation occurred simultaneously, immediately after mitosis, in cultured human lymphocytes. Evidence is presented that in late telophase and post-telophase, the individual nucleolar organising site includes two components, represented in post-telophase by the nucleolus and its attached process; that fusion can be either directly between the nucleoli or via the processes; and that the latter type of fusion persists into metaphase as acrocentric associations, whilst the former is lost.

Number of nucleoli in Ehrlich tumor cells during interphase

Fractions of mouse Ehrlich ascites tumor cell populations with a high percentage of cell either in early or in late interphase were separated by centrifugation on ficoll gradients. Nucleoli were studied by light or electron microscopy in these cell subpopulations. It was shown that, in these cells, the number of nucleoli per nucleus does not vary significantly during interphase. This result is discussed and an anlysis of the relationships between the number and the volume of the nucleoli in these cells is present.

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.