Estimation of haploid cell content of parthenogenetic turkey embryos: A cytofluorometric study

Parthenogenesis in birds: a review

Parthenogenesis or 'virgin birth' is embryonic development in unfertilized eggs. It is a routine means of reproduction in many invertebrates. However, even though parthenogenesis occurs naturally in even more advanced vertebrates, like birds, it is mostly abortive in nature. In fact, multiple limiting factors, such as delayed and unorganized development as well as unfavorable conditions developing within the unfertilized egg upon incubation, are associated with termination of progressive development of parthenogenetic embryos. In birds, diploid parthenogenesis is automictic and facultative producing only males. However, the mechanisms controlling parthenogenesis in birds are not clearly elucidated. Additionally, it appears from even very recent research that these mechanisms may hinder the normal fertilization process and subsequent embryonic development. For instance, virgin quail and turkey hens exhibiting parthenogenesis have reduced reproductive performance following mating. Also, genetic selection and environmental factors, such as live virus vaccinations, are known to trigger the process of parthenogenesis in birds. Therefore, parthenogenesis has a plausible negative impact on the poultry industry. Hence, a better understanding of parthenogenesis and the mechanisms that control it could benefit commercial poultry production. In this context, the aim of this review is to provide a complete overview of the process of parthenogenesis in birds.

Nonlinearity of nuclear enlargement in hepatocytes induced by the carcinogen N'-nitrosomorpholine in Ovo

In this study we investigated the effects of different doses of the carcinogenic nitrosamine N'-nitrosomorpholine (NNM) on the occurrence of enlarged nuclei in embryonic turkey liver in order to evaluate whether this parameter might represent a quantitative indicator of chemically induced hepatocarcinogenesis. Therefore fertile embryo turkey eggs were injected with NNM over a dose range of 125 microg-8 mg/egg at the first day of incubation. After incubation for 24 days, the embryonic livers were removed and processed for histologic evaluation. The induction of hepatocytes with enlarged nuclei (nuclear profiles > 35 microm2 was quantitated morphometrically in hematoxylin and eosin (H&E)-stained sections. The NNM treatment increased both the number of enlarged hepatocyte nuclei and the areas of the individual profiles of the enlarged nuclei in a dose-dependent manner. Exposure to 500 microg-8 mg NNM/egg resulted in a statistically significant increase in the number of hepatocytes with enlarged nuclei. The lower doses of 250 microg and 125 microg NNM/egg showed a similar albeit not significant trend. Signs for cytotoxic effects on the hepatocytes, such as necrosis or enhanced cytoplasmic vacuolization, were observed in tissue samples of embryos exposed to 4 or 8 mg NNM, but not after treatment with lower doses. The dose-effect curve for the induction of the nuclear enlargement was nonlinear, with a moderate slope for lower dose levels of 125-500 microg/egg and a steep slope for higher dose levels of 1-8 mg. Findings in rodents indicate a pathogenic link between the occurrence of enlarged nuclei and hepatocarcinogenesis. Based on the results with NNM, it is suggested that the in ovo model may represent a rapid, convenient, and inexpensive experimental approach for dose effect investigations on chemically induced hepatocarcinogenesis.

Observations on ploidy of cells and on reproductive performance in parthenogenetic turkeys

Using flow cytometry, the ploidy levels of parthenogenetic turkeys were quantified from blastodisc stage to adulthood. Eggs were collected from noninseminated hens of the Beltsville Small White flock, known for their high degree of parthenogenesis, and the blastodermal cells from developing embryos were compared with those of embryos produced by hens inseminated with semen from males of the same flock. Erythrocytes of parthenogens from Day 10 of incubation to 27 mo of age were also used for ploidy determination. Sperm and erythrocyte preparations from normal males of the above flock served as haploid and diploid standards, respectively. In parthenogenetically developing blastoderms, 40.3 +/- 14.5% of the cells were haploid and 48.9 +/- 11.9% diploid; blastoderms from fertilized eggs had no haploid cells. The haploid cell content of parthenogens declined from the blastodermal stage to adult life, with 1.9 +/- 2.3% at 10 to 20 d of embryonic development, 1.5 +/- 1.4% at 21 to 29 d of development, 1.4 +/- 2.6% at 4 wk posthatch, and 1.3 +/- 1.9% in adulthood, although changes between the 1st mo after hatch and adult stage were not significant. It is possible, therefore, that parthenogenetic embryos with a low proportion of haploid cells could be the ones that survive to Day 10 of development and beyond, whereas those with a higher proportion of haploid cells fail to develop. The semen volume of male parthenogens was significantly lower than that of normal males, although the concentration of spermatozoa and their fertilizing capacity did not vary significantly between groups, suggesting that the germ cells of these parthenogens are capable of normal meiosis and sperm maturation leading to a normal fertility.

An evaluation of Econazole, an antifungal agent, for use in quantitative cell culture experiments

Econazole, an imidazole derivative with high antifungal activity, was tested for cytotoxicity using five sensitive tests of human cell function in vitro: colony forming efficiency, growth rate, cell cycle distribution of a permanent epithelioid cell line (T-1E), and attachment efficiency and urokinase production by early passage human embryonic kidney cells. None of these endpoints was detectably affected by 1 microgram/ml Econazole in serum containing medium. At 3 micrograms/ml, Econazole reduced slightly the growth rate of T-1E cells but did not detectably affect the other end points.