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Biomedical subjects

W M Zheng

Publications and source records attributed to W M Zheng.

4 recordsLinked to original sources

A system control framework for the self-fertilization and selection process of breeding.

The self-fertilization and selection process is the main method for speeding up the purifying course of a hybrid population in breeding. This is a complex combinatorial random process with large time delay. To raise the control effectiveness and efficiency of the process, we try, in this paper, to construct a mathematical model of the process by means of effective factors. Then, a control framework for the process is presented which can be used as a guide by breeders for helping them in selecting appropriate control actions.

Fertilization

Gene (effective factor) model and its estimation.

In order to analyze quantitative characters effectively, a gene (effective factor) model is established, which can describe the phenotypic distribution of a quantitative character in the segregating population quite well because it has not only involved the additive effect of genes, but has also considered the dominance deviation and epistatic deviation. In this paper, we also present a method to estimate the parameters of the model. Based on the results of some illustration, the proposed model is considered to be superior to Castle-Wright's formula, and it may provide more useful information to breeders.

Genes

The effect of intrauterine devices (stainless steel ring, copper-T220 and levonorgestrel) on the DNA content in isolated human endometrial cells.

The effect of three different intrauterine devices on the DNA content in human endometrial cells has been studied in 29 women before and after the insertion of an IUD; a stainless steel ring (9 subjects), Copper-T220 (11 subjects) and a medicated IUD releasing levonorgestrel at a rate of 2 micrograms/day (9 subjects). The material was grouped into "bleeders" (having more than 8 days of bleeding and spotting per month) and "non-bleeders" (having less than 8 days of bleeding and spotting per month). The DNA content was assessed on isolated endometrial cells smeared from thin biopsies and the amount of DNA per cell nucleus was measured by means of a Feulgen microspectrophotometric method. No significant difference was found between the "bleeders" and the "non-bleeders" as to the DNA content. Nevertheless, when the total number of subjects were pooled together, a significant increase in the DNA content was found in the post-insertion specimens in the groups of women using the SS and the T-Cu IUDs. Furthermore, a significant decrease in the DNA content was also found when the specimens obtained after the insertion of the LNG IUD were compared with those obtained after 24 months' use of the stainless steel ring and the Copper-T220 device (p less than 0.01 and p less than 0.002, respectively). It is concluded that the insertion of an inert IUD or an T-Cu IUD, induces significant alterations in the DNA content of the human endometrium adjacent to the device, whereas the use of the LNG device does not significantly modify the DNA synthesis when used for 3-10 months. No correlation was found between the DNA content per cell and the number of days of bleeding and spotting.

Adult