Biomedical subjects

E M Walters

Publications and source records attributed to E M Walters.

12 recordsLinked to original sources

PubMed2006

Estrogenic effects of genistein on reproductive tissues of ovariectomized gilts.

The soybean phytoestrogen genistein has a range of estrogenic actions demonstrated in various species; however, only limited research has been done to investigate its effects in swine. The objective of this study was to characterize the effects of a graded dose of genistein on estrogen-sensitive uterine and cervical tissues in ovariectomized gilts. Thirty-four postpubertal gilts were ovariectomized and assigned randomly to 1 of 6 treatment groups 15 d postovariectomy. Treatment groups received vehicle, estradiol benzoate (2 mg/d), or genistein (50, 100, 200, or 400 mg/d) via intramuscular injection at 12-h intervals for 10 d. Following the treatment period, gilts were euthanized, and uterine and cervical tissues were collected and processed for chemical or histological analysis. Uterine and cervical tissue mass, as indicated by wet, dry, and protein weights and total DNA content (expressed per 100 kg of BW), increased as the dosage of genistein increased (P < 0.001 for each regression). Uterine and cervical wet weights were increased by a dosage of 200 mg of genistein/d (P < 0.001 and P < 0.01, respectively) but not by 100 mg of genistein/d (P = 0.38 and P = 0.14, respectively) compared with those of control gilts. Height of epithelial cells lining the uterine glands and the lumen of uterus and cervix increased when gilts were treated with estradiol benzoate or 400 mg of genistein/d (P < 0.01). When the gilts were treated with estradiol benzoate or 400 mg of genistein/d, immunohistochemical staining demonstrated an increase in the percentage of cells that stained positive for progesterone receptor in the uterine glands and in the cells lining the vaginal cervix (P < 0.05). In gilts treated with 400 mg of genistein/d, the percentage of cells stained positive for proliferating cell nuclear antigen increased in the epithelium of the uterine glands, uterine lumen, and vaginal cervix (P < 0.05). Tissue growth was stimulated by genistein in a dosage-dependent manner, although no dosage of genistein induced a response as great as that of estradiol benzoate. Estrogen-sensitive tissues of the ovariectomized gilt, such as the cervix and uterus, are affected by injection of large dosages of the phytoestrogen genistein. The sensitivity of the uterus of the gilt to estrogenic substances makes it a potential model to examine the impact of environmental endocrine modulators on reproductive tissues.

Animals↗

PubMed2003

Transgenic animals in biomedicine and agriculture: outlook for the future.

Transgenic animals are produced by introduction of 'foreign' deoxyribonucleic acid (DNA) into preimplantation embryos. The foreign DNA is inserted into the genetic material and may be expressed in tissues of the resulting individual. This technique is of great importance to many aspects of biomedical science including gene regulation, the immune system, cancer research, developmental biology, biomedicine, manufacturing and agriculture. The production of transgenic animals is one of a number of new and developing technologies that will have a profound impact on the genetic improvement of livestock. The rate at which these technologies are incorporated into production schemes will determine the speed at which we will be able to achieve our goal of more efficiently producing livestock, which meets consumer and market demand.

Agriculture↗

PubMed2002

Use of energy substrates by various stage preimplantation pig embryos produced in vivo and in vitro.

The aim of in vitro embryo systems is to produce embryos of comparable quality to those derived in vivo. Comparison of embryo metabolism as an indicator of viability may be useful in optimization of culture conditions. The aim of the present study was to determine glucose, glutamine and pyruvate use by various stage pig embryos produced in vitro and in vivo. The results indicate that pig embryos use glucose via glycolysis in significant amounts at all stages examined, regardless of embryo origin. In vitro-derived embryos have significantly increased glycolytic activity after the eight-cell stage, whereas in vivo-derived embryos have increased glycolysis at the blastocyst stage. In vivo-derived embryos have higher rates of glycolysis compared with in vitro-derived embryos. Glucose usage through the Krebs cycle for in vitro- and in vivo-derived embryos increased significantly at the blastocyst stage. Pig embryos produced in vitro used constant amounts of glutamine throughout development, whereas in vivo-derived embryos increased glutamine usage after the eight-cell stage. Pyruvate use was minimal at all stages examined for both in vitro- and in vivo-derived pig embryos, showing significant increases at the blastocyst stage. Krebs cycle metabolism of pyruvate, glutamine and glucose by in vivo-derived embryos was higher than that by in vitro-derived embryos. Current in vitro culture conditions produce pig embryos with altered metabolic activity, which may compromise embryo viability.

Analysis of Variance↗

PubMed2001

Transgenic technology and applications in swine.

The introduction of foreign DNA into the genome of livestock and its stable integration into the germ line has been a major technical advance in agriculture. Production of transgenic livestock provides a method to rapidly introduce "new" genes into cattle, swine, sheep and goats without crossbreeding. It is a more extreme methodology, but in essence, not really different from crossbreeding or genetic selection in its result. Several recent developments will profoundly impact the use of transgenic technology in livestock production. These developments are: 1) the ability to isolate and maintain in vitro embryonic stem (ES) cells from preimplantation embryos, embryonic germ (EG) and somatic cells from fetuses; and somatic cells from adults, and 2) the ability to use these embryonic and somatic cells as nuclei donors in nuclear transfer or "cloning" strategies. Cell based (ES, EG, and somatic cells) strategies have several distinct advantages for use in the production of transgenic livestock that cannot be attained using pronuclear injection of DNA. There are many potential applications of transgenic methodology to develop new and improved strains of livestock. Practical applications of transgenesis in livestock production include enhanced prolificacy and reproductive performance, increased feed utilization and growth rate, improved carcass composition, improved milk production and/or composition and increased disease resistance. Development of transgenic farm animals will allow more flexibility in direct genetic manipulation of livestock.

Animals↗

PubMed1984