Biomedical subjects

D K Niu

Publications and source records attributed to D K Niu.

4 recordsLinked to original sources

PubMed2001

Margulis' theory on division of labour in cells revisited.

Division of labour is a marked feature of multicellular organisms. Margulis proposed that the ancestors of metazoans had only one microtubule organizing center (MTOC), so they could not move and divide simultaneously. Selection for simultaneous movement and cell division had driven the division of labour between cells. However, no evidence or explanation for this assumption was provided. Why could the unicellular ancestors not have multiple MTOCs? The gain and loss of three possible strategies are discussed. It was found that the advantage of one or two MTOC per cell is environment-dependent. Unicellular organisms with only one MTOC per cell are favored only in resource-limited environments without strong predatory pressure. If division of labour occurring in a bicellular organism just makes simultaneous movement and cell division possible, the possibility of its fixation by natural selection is very low because a somatic cell performing the function of an MTOC is obviously wasting resources. Evolutionary biologists should search for other selective forces for division of labour in cells.

Cell Division↗

PubMed1997

Evolutionary advantages of cell specialization: save and protect DNA.

As the transcribed regions of nuclear DNA are in a more open state, they are liable to be damaged by naturally or environmentally produced mutagens. Cell specializations make it possible to express fewer genes in individual cells of multicellular organisms, thus protecting genes from the damage of mutagens. We propose that this might account for the advantage of cell specialization, as an alternative to the traditional conception that cell specializations result in increased efficiency. The most efficient cell specialization to protect DNA is in the segregation of germ cell(s) and somatic cell(s). But in optimal environments, such specialization is expected to reduce the rate of reproduction, which might counteract its advantage of protecting DNA.

Animals↗

PubMed1995

Why animals have tumours.

From the viewpoint of an evolutionary biologist, carcinogenesis should be looked upon as a protective mechanism against destruction of DNA. Because genes expressed in embryonic cells are covered and protected by heterochromatinization, they are the most appropriate 'alternate genes' compared to genes that are expressed already in somatic cells. When DNA-damage occurs, the embryonic genes can be activated. Some somatic cells exhibit some features of embryonic cells.

Animals↗

PubMedDate not supplied

Ideas in theoretical biology. Origin of cancerous cells from tumours.

With a previous paper (Niu & Wang, 1995), a general, hypothetical outline of the mechanism of carcinogenesis was proposed. With reference to the fact of starvation-induced hypermutation in micro-organisms, we propose that the hypoxia commonly seen in the cells at the centre of solid tumours might also result in hypermutation, and then p53-dependent programmed cell death. Like the apparently adaptive mutations in micro-organisms, only those genes (e.g. p53) that enable the cells to escape from apoptosis may be selected.

Animals↗