Cell Size and Nuclear DNA Content in Vertebrates

Szarski, Henryk

doi:10.1016/s0074-7696(08)61648-4

Cited by 122 publications

(50 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…15). Furthermore, increased cell sizes lead to decreases in rates of cell metabolism, cell proliferation, and differentiation (17,(21)(22)(23)(24)(25)(26). Animals with large genomes and large cells have fewer cells, including nerve cells, owing to reduced cell-proliferation rates.…”

Section: Resultsmentioning

confidence: 99%

Cell size predicts morphological complexity in the brains of frogs and salamanders.

Roth

Blanke

Wake

1994

Proc. Natl. Acad. Sci. U.S.A.

137

View full text Add to dashboard Cite

The morphological organization of the brain of frogs and salamanders varies greatly in the degree to which it is subdivided and differentiated. Members of these taxa are visually oriented predators, but the morphological complexity of the visual centers in the brain varies interspecifically. We give evidence that the morphological complexity of the amphibian tectum mesencephali, the main visual center, can be predicted from knowledge of cell size, which varies greatly among these taxa. Further, cell size is highiy correlated with genome size. Frogs with small cells have more complex morphologies of the tectum than do those with large cells independent of body and brain size. In contrast, in salamanders brain-body size relationships also are correlated with morphological complexity of the brain. Small salamanders with large cells have the simplest tecta, whereas large salamanders with small cells exhibit the most complex tectal morphologies. Increases in genome, and consequently cell size, are associated with a decrease in the differentiation rate of nervous tissue, which leads to the observed differences in brain morphology. On the basis of these findings we hypothesize that important features of the structure of the brain can arise independently of functional demands, from changes at a lower level of organismal organization this case increase in genome size, which induces simpllifcation of brain morphology.The morphological organization of the brain varies among vertebrates in the degree to which it is subdivided and differentiated. Parts of brains exhibit, among other features, differences in lamination, presence of distinct nuclei, numbers of different cell types, and degree of complexity of neuronal connectivity. There is little understanding of the processes that lead to the observed differences, although the most prevalent explanations are forms of functionalism (i.e., the observed differences are the result of environmental selection regarding the specific function of brain parts) and phylogenetic history (older lineages generally have less complex brains). We have examined an alternative view: that the simple brain morphology of salamanders is secondary, de-rived in large part by pedomorphic evolution associated with increases in genome and cell size (1). We here argue that variation in morphological complexity in the brains of frogs and salamanders is based predominantly on such intrinsic factors and is likely to be independent of direct selection.The brains of frogs (Order Anura) and salamanders (Order Caudata) differ considerably within and among these orders in the degree of morphological complexity. In general, frogs have more complex brain morphology than do salamanders, having morphologically distinct nuclei that often lie in migrated positions in the diencephalon, the pretectum, and the mesencephalic tegmentum (2). In addition, multiple lamination (an alternation of cellular and fibrous layers) is found in the tectum opticum (3, 4), the torus semicircularis (5), and a number of diencephal...

show abstract

Section: Resultsmentioning

confidence: 99%

Cell size predicts morphological complexity in the brains of frogs and salamanders.

Roth

Blanke

Wake

1994

Proc. Natl. Acad. Sci. U.S.A.

137

View full text Add to dashboard Cite

show abstract

“…During developmental and evolutionary processes in normal cells, the DNA content and cell volume maintain a constant ratio (Biodsky&Uryvaena, 1977;Szarski, 1976) as was the case in this fibrosarcoma system. Polyploidization or increasing DNA content may enhance the survivability and growth ability of neoplastic cells under an adverse environment in a similar sense to that postulated for the increased efficiency of normal cells of higher ploidy in developmental and evolutionary processes.…”

Section: Methodsmentioning

confidence: 91%

Malignant properties and DNA content of daughter clones from a mouse fibrosarcoma: differentiation between malignant properties

Suzuki¹,

Williams²,

Hunter³

1980

Br J Cancer

View full text Add to dashboard Cite

Summary.-Freshly isolated clones of high cloning efficiency from a mouse fibrosarcoma were examined for DNA content, cell size, protein content, and malignant characteristics such as artificial lung-colony-forming ability, s.c. tumour take, host survival, and spontaneous metastatic ability.These malignant characteristics and other cell properties were heterogeneous among these clones; the malignant characteristics could vary and were not "all or none" in their nature. The higher the DNA content or the larger the cell volume, the higher the malignancy in terms of artificial lung-colony-forming efficiency, s.c. tumour take, and host survival.Despite variability of each parameter, the ratio of DNA content to cell size or protein content remained constant through these variations: the increased DNA paralleled increased protein and increased cell volume. The increased DNA was correlated with the more malignant characteristics of local growth and lung-colonyforming efficiency.Spontaneous metastasis to the lung was totally different from the local growth abilities; the small-cell clone produced more metastases.The graded nature of malignant properties and the differentiation between local growth and metastatic potential among the daughter clones indicate that malignancy reflects a complex moiety of cell properties.

show abstract

“…The most frequently encountered hypotheses in the literature are that the variation has an adaptive basis and is strongly influenced by natural selection (Sparrow et a!., 1972;Cavalier-Smith, 1978, 1980Price et a!., 1981a). The data are primarily the longstanding interspecific correlations observed between genome size and certain biophysical parameters such as cell or nuclear size and minimum meiotic or mitotic cycle times (Bennett, 1971(Bennett, , 1972Szarski, 1974;Cavalier-Smith, 1978;1982). Organismal phenotypes used to demonstrate these correlations have included body size, clinal or habitat differences, and several life-history characteristics (Ebeling eta!., 1971;Hinegardner, 1974;Bennett, 1976;Mazin, 1980;Shuter et a!., 1983).…”

Section: Discussionmentioning

confidence: 99%

Genome size variation among north american minnows (Cyprinidae). I. distribution of the variation in five species

1985

Heredity

View full text Add to dashboard Cite

Genome sizes (nuclear DNA contents) were examined spectrophotometrically from ten individuals of each of five species of North American cyprinid fishes (minnows). The distributions of DNA values both within and between the five species were essentially continuous and normal. Differences between individuals within populations were significant and contributed to approximately 16 per cent of the total variation. Variation between individuals within species ranged from 47-135 per cent and averaged ca. 7•4 per cent. Variation between species ranged from O-95 per cent and the averaie difference between any species pair was Ca. 46 per cent. Statistical analyses showed that the methodology used was sufficient to detect significant differences in genome size as small as 2-3 per cent. Consideration of these data lead to the following tentative conclusions: (i) changes in genome size in cyprinids appear small in amount, frequent in occurrence, to involve both gains and losses of DNA, and to be cumulative and independent in effect; (ii) differences within and between cyprinid taxa are likely the result of accumulations of small changes in DNA quantity; and (iii) the primary focus of quantitative DNA variation in cyprinids is between individuals within populations. The extent of DNA quantity variation which occurs within species would appear to preclude any direct relationship between genome size variation and many of the organismal parameters (including speciation) which differentiate the five species. In short, the data suggest that a significant fraction of the cyprinid genome, perhaps more than 10 per cent, is free to vary quantitatively without phenotypic constraint or biological consequence. This fraction is considerably larger than that theoretically needed for the structural gene component. INTRODUCTIONA long-standing problem in evolutionary genetics regards the quantitative variation in genome size or nuclear DNA content (the C-value) among eukaryotic organisms. Abundant data are now accumulated which show that large, often spectacular differences in genome size commonly occur between even closely related taxa, and that increases in genome size are not necessarily associated with evolutionary advancement (Bachmann et a!., 1972;Rees and Jones, 1972; Hinegardner, 1976;Price, 1976). Early suggestions (Kauffman, 1971) were that the variation was related to either the number of genes in an organism, its organismal complexity, or both. The general concensus now, however, is that there are no significant correlations between genome size (the C-value) and organismal or genetic complexity (Cavalier-Smith, 1978). This is called the C-value paradox. Other pertinent findings which have emerged are that: (i) increasing organismal specialization in body form and design may often be associated with The underlying causes of genome size variation are not well understood. Much of the data has been interpreted as supporting the idea that the variation has an adaptive basis and is strongly 298 J R. GOLD AND H. JAMES PRICE influenced...

show abstract

Cell Size and Nuclear DNA Content in Vertebrates

Cited by 122 publications

References 44 publications

Cell size predicts morphological complexity in the brains of frogs and salamanders.

Cell size predicts morphological complexity in the brains of frogs and salamanders.

Malignant properties and DNA content of daughter clones from a mouse fibrosarcoma: differentiation between malignant properties

Genome size variation among north american minnows (Cyprinidae). I. distribution of the variation in five species

Contact Info

Product

Resources

About