White Peking Duck Research Articles

Development of the trochlear nerve: Loss of axons during normal ontogeny

Development of the trochlear nerve from day 11 of incubation through hatching was studied in white Peking duck embryos. Counts of fibers from the electron micrograph montages indicate that initially there is an abundant collateral sprouting which roughly coincides with the time of neuromuscular contacts, suggesting some sort of interaction between the developing nerve and the periphery. The maximum number of trochlear cells and fibers is present on day 12. Average cell and fiber counts on this day are 2325 and 47,386 respectively. Assuming all cells send their axons into the nerve and that all cell bodies are present within the trochlear nucleus, the ratio of cells to fibers is 1:20. Average cell and fiber counts at hatching are 1338 and 1506 respectively. Thus, losses of approximately half the trochlear cells and of 97% of the fibers occur during normal development. Degenerating cells and fibers are first observed on day 13. Degeneration involves both the myelinated and the unmyelinated axons. The actual number of degenerating fibers which were observed, however, was very small compared to the number of fibers lost during development; thus, it is suggested that, in the majority of cases, fiber loss is perhaps via retraction of axon collaterals. In general, cell death slightly precedes axon loss, which suggests that the direction of the degeneration is from cell body to the axon. A cell/fiber ratio of approximately 1:1 is first observed on day 18 and remains so thereafter. Indirect evidence is discussed, suggesting that at least some cells which die during normal development had sent their axon into the nerve prior to their death. Whether these axons make meaningful connections with the muscle is uncertain.

Development of the oculomotor nucleus, with special reference to the time of cell origin and cell death

The developmental pattern of the oculomotor nucleus from day 7 of incubation through two weeks after hatching was studied in white Peking duck embryos. The neuroblasts comprising the nucleus complete their last phase of DNA synthesis on days 4 and 5 and the anlage first appears on day 7. The various subnuclei become identifiable as distinct cell groups on day 8 or 9. There is a cell migration between the ventral-most portions of the two ventromedial nuclei on days 9 through 11, and as a result a well-developed oculomotor commissure is established between these two subnuclei. The maximum number of cells in the nucleus is present on day 11. There is a normally occurring overall loss of approximately 43% of the cells during ontogenesis. Cell death appears to be random, without any gradient, and virtually all of it occurs between days 11 and 15. Although the duration of cell death is essentially similar in all subnuclei, great variations exist in its magnitude. For example, there is a cell loss of approximately 61% in the accessory nucleus, 38% in the dorsolateral nucleus, 40% in the dorsomedial nucleus and 33% in the ventromedial nucleus. Cell loss in the oculomotor nucleus is compared with that observed in the other two eye-muscle nuclei.

Developing preferences for live female models of the same or other species in white peking ducklings

The preferences of white Peking ducklings ( Anas platyrhynchos) for live models was evaluated for the first 7 days of life. The models were all females: a rouen duck ( Anas platyrhynchos), a white Peking duck, and a blue Andalusian chicken ( Gallus gallus). In three different experiments the orientation of the models was toward the subjects, away from the subjects, and toward the subjects but with fences around the models (to control for model aggressiveness). In all cases the subjects preferred the rouen duck and not the white Peking model or the chicken. In addition, when the models were facing away from the subjects there was a significant peak of preference that appeared on day 4. The latter effect was replicated three times and is therefore considered a reliable phenomenon.

Autoradiographic studies on the time of origin of neurons of the eye-muscle nuclei

The time of origin of neurons in the various eye-muscle nuclei of white Peking duck embryos was investigated by autoradiography. A single injection of 20 μCi [ 3H]thymidine in aqueous solution was introduced into three embryos each day from days 2 through 10 of incubation. Embryos injected on or before day 3 show heavy labeling of all neurons. In contrast, brains injected on or after day 7 reveal that none of the neurons are labeled. These results indicate that the entire neuronal population of the oculomotor, the trochlear, and the abducens nuclei passes through the final phase of DNA synthesis on days 4, 5, and 6 of incubation. The neurons of the oculomotor nucleus are formed first and those of the abducens nucleus last, which suggests a rostrocaudal gradient in cell generation. A dorsoventral gradient is present in the various subnuclei of the oculomotor complex. Counts of the labeled and unlabeled cells in the brains injected on different days indicate that the cells which die during normal development do not belong to a special class of cells which are generated late in development.

Cell death during normal development of the abducens nucleus

The developmental pattern of the principal abducens nucleus, from Day 7 of incubation through hatching and 2 weeks after hatching, was studied in white Peking duck embryos. The nucleus first becomes recognizable as a distinct cell mass on Day 7. The accessory nucleus completes its ventrolateral migration on Day 8. The maximum number of cells (approximately 2400) in the principal nucleus is present on Day 10 of incubation. On this day, a well-developed abducens nerve leaving the nucleus from its ventral aspect can be easily observed. There is a naturally occurring loss of approximately 50% of the cells. Most of the cell death takes place between Days 11 and 15. Cell counts on Day 15 indicate an average of 1330 cells in the principal nucleus. Cell death, however, continues at a reduced rate until Day 21. Cell number thereafter stays relatively constant. The cell population remains remarkably homogeneous throughout development. The development of the abducens nucleus is compared with that of the trochlear nucleus. Although the magnitude of cell death in the above two cases is comparable, some interesting differences occur. Possible causes of the normally occurring cell death are discussed.

Duck red cell 2, 3 diphosphoglycerate: Its presence in the embryo and its disappearance in the adult

Summary Erythrocytes drawn from embryos of the white Peking duck ( Anas domesticus ) contain appreciable amounts of 2,3 diphosphoglycerate and negligible amounts of inositol hexaphosphate. In the adult, inositol hexaphosphate becomes the major phosphorylated intermediate while 2,3 diphosphoglycerate is no longer detectable by ion-exchange column chromatographic separation and colorimetric assay procedures. This indicates that the metabolic pathways for the biosynthesis of 2,3 diphosphoglycerate and inositol hexaphosphate are influenced differentially during avian development. To our knowledge, this is the first report on the presence of 2,3 diphosphoglycerate in avian erythrocytes.

The development of preferences for live models in white peking ducklings

Live stimulus objects were used to assess the developing preferences of white peking ducklings. The live models were all female and were a rouen duck, a white peking duck, and a blue andalusian chicken. Testing occurred at 8 a.m., 1 p.m., and 6 p.m. The rouen duck. was preferred more than the other models, the time of day had no effect, and no position effect was observed. The technique of using live, biologically appropriate, stimulus objects has much potential for assessing attachment behavior in birds.

Temperature sensitivity of the avian salt gland

Local cooling of the salt glands in the white Peking duck decreased the volume of secretion without affecting the concentration.

Appearance of an embryonic-like hemoglobin in the methotrexate-treated adult white Peking duck.

Methotrexate-induced megaloblastic anemia led to altered proportions of Hbs I and II in the adult Peking duck and to the appearance of the 2 new hemoglobins which we have tentatively labeled Hbs “III” and “X.” One of these, Hb “III,” has electrophoretic and chromatographic properties indistinguishable from Hb III seen only in the embryo and duckling.

HEMOGLOBIN HETEROGENEITY: EMBRYONIC HEMOGLOBIN IN THE DUCKLING AND ITS DISAPPEARANCE IN THE ADULT.

The 7-day white Peking duck embryo contains two hemoglobins (Hb's III and IV) which are electrophoretically distinct from the two adult hemoglobins (Hb's I and II). Hemoglobin IV had disappeared in the 14-day embryo, at which time Hb's I and II are evident. The synthesis of Hb III is not restricted to embryonic life but continues in the duckling and ceases before the 10th week of development after hatching.