Quantitative Aspects of Nuclear Nucleoproteins

Somatic tetraploidy in vertebrate neurons: Implications in physiology and pathology

The presence of polyploid neurons in the vertebrate nervous system has been a subject of debate since the 1960s. At that time, Purkinje cells were proposed to be tetraploid, but technical limitations impeded to reach a clear conclusion, and the current belief is that most vertebrate neurons are diploid. By using up-to-date approaches we have recently demonstrated the existence of a subpopulation of tetraploid retinal ganglion cells (RGCs) in the vertebrate retina. In the chick, these neurons show large somas and extensive dendritic trees and most of them express a marker specific for RGCs innervating a specific lamina of the optic tectum. We have also demonstrated that these neurons are generated in response to nerve growth factor (NGF) acting through the neurotrophin receptor p75 (p75(NTR)), which induces E2F1 activity and cell cycle re-entry in migrating RGC neuroblasts lacking retinoblastoma (Rb) protein. We have also showed that brain-derived neurotrophic factor (BDNF) prevents G(2)/M transition in the tetraploid RGCs, thus being crucial for the maintenance of the tetraploid status as well as the survival of these neurons. The realization that tetraploid neurons can be readily observed in the vertebrate nervous system has important physiological consequences, which are discussed in this commentary.

Control of neuronal ploidy during vertebrate development

Somatic tetraploid neurons are present in different structures of the vertebrate nervous system, including cortex and retina. In this chapter, we provide evidence that these neurons can be widely detected in the chick nervous system. We also discuss mechanisms creating neuronal tetraploidy in vertebrates, concluding that the neurotrophin receptor p75 could be responsible for the generation of these neurons in most neural tissues, as previously observed in the retina. Somatic tetraploidy in the chick retina correlates with increased neurons' soma size and dendritic arborization, giving rise to neurons known to innervate a specific layer of the optic tectum. Tetraploidy could therefore account for neuronal diversity in the normal nervous system. De novo generation of tetraploid neurons has been shown to occur in Alzheimer's disease. This suggests that the morphological changes expected to occur in the affected neurons could lead to altered neuronal function, thus providing a basis for neurodegeneration.

The puzzle of ploidy of Purkinje neurons

This paper places attention on the discrepancies existing in the literature on the ploidy of Purkinje neurons and focuses on the special case of partial replication of their genome and on the unequal frequency of polyploid Purkinje neurons in the cerebellar cortex of the lobes and the vermis. Owing to the compartmental structure of the cerebellum, this paper suggests the investigation with modern methods and techniques of other cerebellar regions such as the flocculus, with the aim of establishing whether increased ploidy correlates with cell hypertrophy and/or with stimulation of cerebellar functions.

Abnormalities of DNA in human osteoarthritic articular cartilage

The normal amount of DNA in human diploid nuclei was determined by the use of the Feulgen reaction measured by microdensitometry. The DNA-content of nuclei in normal human articular cartilage was determined in nuclei of zones 3 and 4 of cartilage of the femoral head removed from osteoporotic fractured necks of femur. Analysis of the results indicated that a degree of synthesis of DNA occurred even in these zones of very elderly persons. Results on these zones in the articular cartilage of osteoarthritic joints indicated that different populations occurred. In some there was DNA-synthesis related to tetraploidy; in others, the DNA was very stable to acid hydrolysis with no sign of biosynthetic activity; in the last group, which contained erosions of the superficial zones, the DNA was unstable to hydrolysis.

Flow cytometric analysis of isolated rat liver nuclei during growth

The development of hepatocyte polyploidy in rats aged up to 4 months was analyzed by flow cytometry using both scatter and fluorescent parameters to distinguish DNA diploid and DNA tetraploid populations and to discriminate between parenchymal and non-parenchymal compartments. The precise origin of each class of nuclei was assessed in whole liver homogenate using purified hepatocytes, obtained by liver perfusion followed by separation on Percoll gradient, and identifying the peaks corresponding to parenchymal nuclei. The results indicate that preparative procedures involving homogenization of the rat liver tissue caused loss of the DNA octaploid population. Data on the relative proportion of the different DNA ploidy elements during rat liver development, which are in good agreement with those observed by cell analysis by means of microspectrophotometry, indicate the usefulness of flow cytometry as a choice method for the analysis of ploidy distribution.

Flow cytometry of renal oncocytoma: common occurrence of deoxyribonucleic acid polyploidy and aneuploidy

Flow cytometry was performed on 51 typical specimens of renal oncocytoma. Nuclei were extracted from paraffin-embedded archival material and isolated nuclei were stained with propidium iodide. Of the 51 available tissue blocks 86 per cent were evaluable and 50 per cent of these samples showed a deoxyribonucleic acid (DNA) histogram that was approximately the same as normal renal parenchyma. Of the oncocytoma samples 39 per cent showed a marked increase (more than 10 per cent of the nuclei) in the tetraploid DNA peak, while 11 per cent showed a distinct DNA aneuploid peak. Among 21 evaluable grade 2 oncocytic renal tumors 33 per cent showed a normal DNA histogram, 43 per cent showed a marked increase in the DNA tetraploid peak and 24 per cent showed a DNA aneuploid peak. The common presence of polyploid nuclei containing double quantities of chromosomal DNA may correlate with the long-standing pathological observation that oncocytic tumors often contain a distinct population of large nuclei. Indeed, 86 per cent concurrence was seen between the detection of an abnormal DNA content by flow cytometry and the histopathological presence of large abnormal nuclei in these specimens. Since renal oncocytomas (grade 1 oncocytic tumors) rarely, if ever, metastasize and are relatively noninvasive locally, their markedly abnormal flow cytometry patterns are of considerable interest. Moreover, DNA polyploidy has not been identified previously in renal tumors. The biological significance and mechanism of DNA polyploidy, and the relationship of DNA polyploidy and DNA aneuploidy to the pathogenesis of oncocytic renal tumors require further laboratory investigation. The clinical use of flow cytometry to classify and to predict the behavior of renal tumors will be complicated, since renal oncocytomas commonly have polyploid and aneuploid DNA histograms.

Air drying as a preparatory factor in cytology: investigation of its influence on dye uptake and dye binding

The effect of air-drying on cytological material is investigated in this article. Smears of rat liver were fixed completely wet and, after air drying, postfixed in ethanol, methanol/formaldehyde/acetic acid (MFA), and formaldehyde. Staining was performed with the thionin-Feulgen procedure, a standard Romanowsky-Giemsa stain with azure B-eosin Y and a Papanicolaou staining variant. The image analysis system IBAS 2000 was applied to evaluate objective criteria of the changes caused by air drying the chromatin texture. Nuclear absorption was measured with a Vickers M 85a Microdensitometer. Air-drying had striking effects on size and shape of cell nuclei (spreading), on the structure of the nuclear chromatin (chromatin condensation), and on the chromaticity coordinates (hue, saturation, and intensity of nuclear staining). The variations of the chromatin texture and dye-substrate affinity are attributed to alterations of the tertiary structure of the nuclear proteins.

Different instability of nuclear DNA at acid hydrolysis in cancerous and noncancerous cells as revealed by fluorescent staining with acridine orange

Ehrlich cancer cells and inflammatory cells in mouse ascitic fluid were hydrolyzed and stained with acridine orange (AO). The AO hydrolysis curves for G1/G2 + M phase cancer cells and inflammatory cells were differentially determined using flow cytometry by monitoring the metachromatic red-shifted fluorescence of the fluorochrome bound to the single-stranded DNA produced by acid hydrolysis. By computer fitting of the Bateman function to the hydrolysis curves, the kinetic parameters k1 (rate constant for the production of single-stranded DNA), k2 (rate constant for the degradation of the produced single-stranded DNA), and y0 (theoretical value of the single-stranded DNA present initially) were determined. It was found that the k2 value, which reflects the degree of DNA instability, was much higher for cancer cells in both the G1 and G2 + M phases than for inflammatory cells. This finding led us to develop a method for the differential AO staining of cancer cells and non-cancerous cells utilizing the different degree of DNA instability at acid hydrolysis. AO staining after hydrolysis with 2N HCl at 30 degrees C for 8.5 min was found to be the optimal method. In the 60 cases of human malignant epithelial and nonepithelial tumors tested, all of the malignant tumor cells emitted metachromatic red fluorescence, while all of the nonmalignant tumor cells (5 cases of benign tumor) and normal cells emitted orthochromatic green fluorescence when observed with a violet excitation light under a fluorescence microscope. This new technique can be a useful tool for the screening of malignancy in exfoliative cytology and also for basic cancer research.

Changes in Polyploidy During Aging in Human Liver

The level of liver polyploidy was compared in three groups of humans: a young group aged 20–46, an older group aged 62–68 and the oldest group aged 70–79. The most important trend showed by the data was that there is a depletion of 2N and 4N cells, accompanied by an increase in 8N and 16N cells as a function of advancing age. There was a high degree of variability in the percentage of cells in each ploidy class from one individual to the next for all age groups. For this reason, polyploidy appears to be a less effective biomarker of aging in humans than it is in experimental animals.

Occurrence of polyploidy and multinuclearity in the differentiating liver of chick embryo

Increase in nuclear size in liver has been used as an index of polyploidy. It has long been considered that the occurrence of polyploidy and multinuclearity are characteristics of mammalian liver. The present study shows the occurrence of these phenomena in the liver of birds, so these features are not confined to mammals. 3 classes of nuclear size groups have been identified. The simultaneous occurrence of polyploidy and binuclearity indicates some sort of interrelationship between them.

The effect of cervical mucus on measurable Feulgen DNA content of human spermatozoa

The DNA content of morphologically normal Feulgen-stained human spermatozoa (SP) without and with vacuoles was determined by visible light absorption at 560 nm. In an experimental device designed according to the sperm penetration meter of Kremer, sperm penetration into cervical mucus (CM) was allowed to take place for a 60-min period. Smears of the native and mucus-penetrated spermatozoa were applied to glass slides and fixed in a mixture of methanol, formalin, and acetic acid for 1 h. Hydrolysis was performed in 1 N HCl. The slides were stained using hematoxylin. Bull spermatozoa stored at -96 degrees C were applied as an internal standard to ach slide. Of a total of 1,464 spermatozoa measured, 485 came from the ejaculate, 491 had travelled through the cervical mucus for a distance of 15-30 mm, and 193 had migrated for 31-45 mm. The remaining 295 bull spermatozoa were also measured. It was found that after cervical mucus passage the content of Feulgen DNA material measured changed in two different ways: in some of the samples the Feulgen DNA content increased with passage through the cervical mucus, whereas in other samples the Feulgen DNA content decreased during cervical mucus passage. As in the ejaculate, we found a marked variation of the DNA content of spermatozoa after CM passage. The filtering effect of the CM on pathologic SP was not complete.

Absorption spectrum of Feulgen-stained polytene chromosomes of Drosophila melanogaster

Hetero- and euchromatic polytene chromosome regions of early and fully grown larvae of Drosophila melanogaster had their Feulgen absorption curves determined cytophotometrically. Hydrolysis conditions adequate to induce maximal DNA depurination were used. No differences in curve shapes specially concerning the absorption shoulder at the 520 less than or equal to lambda less than or equal to 550 nm spectral range were detected with advancing polytenization or when comparing the absorption patterns for the hetero- and euchromatic regions to each other. It is considered that prominence of the Feulgen absorption shoulder could be related to the amount of Schiff molecules di-substituted with apurinic acid aldehydes and to the relatively larger resistance of these apurinic acid fragments towards solubilization with acid hydrolysis due to their binding to nuclear proteins. It is therefore assumed that no significant differences owing to the above-cited factors exist for the chromosome regions analyzed at 2 phases of the polytenization process. Consequently, the replication of reiterated sequences from the main band DNA which occurs in polytene chromosome regions of Drosophila melanogaster appears not to affect the Feulgen absorption spectrum of this material.

Feulgen-DNA absorption curves of polytene chromosome regions of Rhynchosciara americana

Feulgen absorption spectra of polytene chromosome regions, differing in types of DNA composition and of chromatin compactness, were determined microspectrophotometrically in squashed salivary glands of Rhynchosciara americana. The absorption curves exhibited a secondary maximum at their ascending branch after the chromatins were maximally depurinated. The degree of shoulder prominence could not be specifically correlated with the packing state or even with richness in satellite repetitive DNA of the chromatins. It is assumed that other factors may exist which play a part in the phenomenon that gives rise to the Feulgen absorption shoulder characteristics. Differences in the extraction rate of the apurinic acid fragments due to their binding to specific non-histone proteins are suggested as contributing to the above-mentioned absorption patterns when comparing the various chromatin types.

Matrix formation in craniofacial cartilages of the rat. [35S]-sulfate incorporation studies

Various cartilaginous zones in the craniofacial region of rats were studied using radioactive sulfate incorporation. Chondroitinsulfate represents a major part of the cartilaginous matrix. By measuring the cpm/DNA ratio in the tissue samples, one will get an expression of the matrix formation activity of the zones investigated. An increase in the cpm/DNA ratio was found in all zones between the 14th and the 17th day. This increase corresponds with a period of great proliferative activity. Autoradiography of the mandibular condyle revealed no sulfate labelling centrally indicating that this structure grows purely by surface apposition.

Co-replication of satellite DNA of Chironomus melanotus with mainband DNA during polytenization

The DNAs of five Chironomus species, C. plumosus, C. nuditarsis, C. thummi thummi, C. melanotus, and Camptochironomus pallidivittatus, were investigated in analytical neutral isopycnic CsCl density gradients. DNA was isolated both from larval brains ("diploid-DNA") and salivary glands ("polytene-DNA"). The buoyant densities of mainband DNAs were 1.692 g/cm3, with the exception of C. melanotus whose mainband had a density of 1.693 g/cm3. The densities correspond to a calculated GC content of 33% and 34% respectively. Only in C. melanotus was the DNA clearly resolved into mainband DNA and two distinct satellite shoulders: Satellite I, with a buoyant density of 1.684 g/cm3 (25% GC, calculated) and satellite II of 1.679 g/cm3 (19% GC, calculated). The two satellites comprise 15% of the total DNA in the "diploid-DNA"' and they also occur in the "polytene-DNA", where they make up 11%. The results are discussed in the general context of under- and overreplication in polyploid and polytene cells.

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.

Prospects for microscopical cytochemistry

This review is devoted mainly to an evaluation of the status of microscopical cytochemistry seen as a discipline aiming at both the localization and the quantification of molecular processes in cells. Its relationships to ultramicrochemistry, as well as, in a broader sense, to biochemistry and cell biology, are discussed from both the historical and the methodological points of view. Recent developments in quantitative cytophysical techniques, such as automated cytophotometry using microscopes fitted with flying spot systems, TV cameras, or scanning stages, and the development of rapid flow cytometers are discussed. Analytical electron microscopy is touched upon too. The main part of the review is devoted to recent trends that strengthen the analytical basis of cytochemical staining methods. The special character of staining procedures as a kind of matrix chemistry is discussed and the potentialities of the use of matrix-incorporated compounds for the fundamental study and calibration of microscopical staining procedures are elaborated. Parallel developments in the theory and practice of matrix chemistry in biochemistry are stressed. Growing interrelations between microscopical cytochemistry and related fields of investigation, such as the controlled fragmentation of cells, and methods like ultramicroanalysis of individual cells are indicated.

DNA and the cell cycle

The cell cycle and its significance for pathology is reviewed. The molecular basis and questions of regulation in the cell cycle are discussed, along with deviations from the normal cycle in the form of polyploidy formation and aneuploidy in tumor cells. Automated prescreening processes may play a role in the future in daily routine diagnosis. Methods of cytophotometry with the possibility for objective pattern recognition will become significant in pathology in many ways, both in research and in routine work.

GROWTH OF POLLEN GRAIN NUCLEI OF TRADESCANTIA PALUDOSA

Pollen grain nuclei of Tradescantia paludosa Anderson and Woodson had a mean volume of 122 μm3 in early G1 and 1,415 μm3 in late G2. The distribution of nuclear volumes was not linear normal; however, it closely approximated a log normal distribution and probit plots yielded straight lines for the central 85-90% of the values. Most nuclei were spherical or nearly-spherical in early G1 but their increase in volume was accompanied by a change to an ovaloid or elongate shape. Interphase in the pollen grain lasted about five days at 25 °C. In the first 3.5 days the rate of increase in mean nuclear volume was about 87 μm3 per day. In the last 1.5 days of pollen grain interphase, nuclei increased at a mean rate of 658 μm3 per day; nuclear growth was relatively slow in G1 and rapid in G2. The largest nuclei tended to divide first; the result was that as the proportion of nuclei that have divided increased, mean nuclear volume decreased from 1415 μm3 to 680 μm3. Nuclear volumes were also determined for diploid nuclei of root meristem and sporogenous cells; their mean volumes were smaller, 1,355 μm3 and 1,018 μm3, than that of the G2 haploid nuclei, 1,415 μm3.

Nuclear dna amounts in angiosperms

The number of angiosperm species for which nuclear DNA amount estimates have been made has nearly trebled since the last collected lists of such values were published, and therefore, publication of a more comprehensive list is over due. This paper lists absolute nuclear DNA amounts for 753 angiosperm species. The dats were assembled primarily for reference purposes, and so the species are listed in alphabetical order, as this was felt to be more helpful to cyto- and biochemists whom, it is anticipated, will be among its major users. The paper also reviews aspects of the history, nomenclature, methods, accuracy and problems of nuclear DNA estimation in angiosperms. No attempt is made to reconsider those aspects of nuclear DNA estimation which have been fully revised previously, although the bibliography of such aspects is given. Instead, the paper is intended as a source of basic information regarding the terminology, practice and limitations of nuclear DNA estimation, especially by Feulgen microdensitometry, as currently practiced.

Percent satellite DNA as a function of tissue and age of mice

A selective loss of satellite DNA was found to occur to different extents as a function of tissue and age of mice using several common DNA extraction and purification procedures. This result emphasizes a serious problem that may be encountered in comparative studies of DNA structure and composition if selective loss of specific DNA sequences occurs. We have developed a DNA extraction and purification procedure that is simple and reliable and gives a high percent DNA yield, which substantially reduces the selective loss of heterochromatin DNA sequences. The method features a centrifugation step of a proteolytic digest of chromatin in 2.4 M CsCl. Percent DNA yield of 82-98% are routinely obtained with no apparent loss of satellite DNA sequences from different tissues or ages of mice. Utilizing this method, percent satellite DNA was found to remain essentially constant at 11 +/- 1% for spleen, kidney, and brain tissues obtained from mice of 10-780 days of age. However, for liver, percent satellite DNA remained at about 7-8% from 10 to 300 days of age and then increased to about 12-13% from 300 to 600 days of age. During this latter time interval (300-600 days), an increase of DNA per nucleus of about 3-fold occurred, due to the formation of tetra- and octaploid cell types. A steady loss in the total number of nuclei per gram of liver as a function of age was also found. These two opposing effects resulted in a nearly constant amount of DNA per gram and per organ for liver throughout the lifespan of the mouse.

Microspectrophotometric estimates of non-histone proteins in cell nuclei displaying differing degrees of chromatin condensation

Nuclei isolated from mouse thymus, kidney, and liver were fixed in ethanol-acetic acetic acid; treated with dilute acid to extract histones; stained by three protein end-group procedures; and measured by scanning, integrating microspectrophotometry. Measurements were also made of nuclei isolated from the same organs and stained by the Feulgen procedure for DNA. Protein end-group procedures included pH 2.8 Biebrich scarlet (for basic groups), mercury orange (for sulfhydryl groups), and mercury orange after thioglycolate reduction (for the sum of sulfhydryl and disulfide groups). With the exception of the comparison between Feulgen-stained 2C liver and kidney nuclei, the integrated extinction values obtained for nuclei of a given organ differed significantly from the measurements of nuclei from other organs, regardless of the staining procedure. Furthermore, the integrated extinction values for 2C nuclei were highest in larger, more vesicular nuclei (from liver and kidney) and lowest in condensed thymocyte nuclei, except in the case of measurements of the disulfide content of the nuclei. In this instance, the values of integrated extinction were highest in condensed thymocyte nuclei, intermediate in kidney nuclei, and lowest in 2C liver nuclei. When 2C, 4C, and 8C liver nuclei were compared, the integrated extinction values of 4C nuclei were found to be approximately twice those of 2C nuclei whose disulfide and Feulgen values were, respectively, higher and lower than expected. The greater disulfide values and reduced Feulgen values obtained in thymocyte and 8C liver nuclei might be related to a greater degree of chromatin condensation in these nuclei, and therefore, to a reduction or selective restriction of their RNA transcriptional capacities.

Cytokinins and nuclear RNA levels in onion root tips

Onion root tips were grown in water, kinetin or 6-benzyladenine and levels of RNA in the chromatin region of nuclei were analyzed using visible light microscopy with basic-dye staining, and ultraviolet microscopy of unstained material. No evidence was found for a significant increase in nuclear RNA in response to cytokinin treatment.