A comparative study of embryonic development of Japanese quail selected for different patterns of postnatal growth.

Patterns of early embryonic development have traditionally been viewed as invariant within vertebrate taxa. It has been argued that the specific differences which are found arise during the later stages of development. These differences may be a result of allometry, heterochrony or changes in relative growth rates. To test whether early embryonic development is indeed invariant, or whether selection of adult characteristics can alter embryonic growth, we compared embryonic development in birds selected for different patterns of postnatal growth. Using quail lines selected for high and low body mass, we compared somite formation, and muscle and feather development. We obtained data that showed changes in the rate of myotome formation in the brachial somites which contribute to muscle formation in the limbs and thorax. We think these observations are connected with intraspecific changes in adult morphology, ie., breast muscle size. Our findings suggest that selection for late ontogenetic/adult stages affects early embryonic development.

On the pattern of organ growth in the common tern (Sterna hirundo).

Data are presented on the pattern of organ growth in the Common Tern, a semi-precocial bird species with a high growth rate, and are compared with data from some bird species within the altricial-precocial spectrum. The data show that a high growth rate is linked to a growth pattern characterized by a rapid early development of the digestive organs and a late development of pectoral muscles and feathers. These results suggest that the growth rate is most likely restricted by the capacity to ingest and digest food. It also appears that the organ growth pattern is more closely related to the growth rate than to the degree of precocity.

Placenta previa, maternal smoking and recurrence risk.

In order to assess the risk of placenta previa among women who smoked during pregnancy and to study the recurrence risk of placenta previa, we analyzed data from the Swedish Medical Birth Registry. Among 1,825,998 infants of women delivered in 1973-1990, 5,683 had placenta previa registered. The overall incidence of placenta previa was 0.3%, the incidence in twin deliveries was also 0.3%. The recurrence rate of placenta previa was 2.4%, which is an eightfold increase compared with the rate of a placenta previa among all births. Maternal smoking was studied for births in 1983-1990 and appeared as an independent risk factor for placenta previa. A dose-response between the number of cigarettes smoked during pregnancy and the risk of having a placenta previa was indicated.

Changes in organ growth pattern associated with long-term selection for high growth rate in quail.

Data are presented on the pattern of organ growth in embryos from a line of Japanese quail selected for high growth rate and compared with those from a non-selected control line. The data reveal that the increased growth rate post hatching is accompanied by a more rapid early development of the digestive organs. It appears from these results that the "genes for" growth rate are the "genes for" early growth of the digestive organs.

Postnatal growth of the liver in the young fieldfare (Turdus pilaris).

In this paper data are presented on the postnatal growth of the body and some organs in the young fieldfare. To the best of our knowledge the fieldfare has the highest specific growth rate ever reported for an avian species. The mitotic activity in the liver has been investigated by means of flow cytometry and autoradiography. It appears that a high rate of liver growth is more nearly related to the relative number of proliferating cells than to the length of the mitotic cycle. Furthermore, it is concluded that the liver has to be large, at least in relation to its functional activities, in order to be able to grow at a very high rate.

Changes in embryonic development associated with long-term selection for high growth rate in Japanese quail.

Selection for rapid growth in the quail resulted in a changed growth pattern of the embryo and the extra-embryonic membranes (the yolk sac and allantois). The early part of the incubation period was characterized by a reduced embryo weight and a more rapid early development of the extra-embryonic membranes. These changes were followed by an increased growth rate of the embryo. The increased growth rate was apparently linked to the more rapid early development of the extra-embryonic membranes. Thus, the growth rate was most likely restricted by the capacity to absorb and utilize yolk. It also appears that at least part of the increase in growth rate was made possible by the change in the early embryonic growth pattern.

Postnatal growth and organ development in Japanese quail selected for high growth rate.

As a result of selection for high growth rate in the quail the organ growth pattern has changed considerably. The main change, which characterizes the early part of the postnatal growth, consists of an increased relative size of the digestive organs and a lowered early growth rate of pectoral muscles and feathers. Since the increase in growth rate is linked to an increase in the relative size of the digestive organs, the growth rate is most likely restricted by the capacity to ingest and digest food. It also appears that at least part of the increase in growth rate is made possible by the change in organ growth pattern.

A comparative study of postnatal growth and organ development in some species of birds.

An hypothesis has been formulated stating that the rate at which postnatal growth proceeds is at least partly determined by the distribution of growth between different organs. In order to test the hypothesis a series of studies of organ growth has been undertaken in some birds with widely varying growth rate capacities (geese, quail, turkeys, fieldfares and jackdaws). With regard to nidifugous birds the data show that the growth pattern of the goose, a species which has a high growth rate capacity, is characterized by a rapid early development of the digestive organs and the liver whereas that of the quail and the turkey, species which have low growth rate capacities, is characterized by a rapid early development of the pectorals and the feathers. The growth pattern of the nidicolous species, the fieldfare and the jackdaw which also show high growth rate capacities, is similar to that of the goose. These results are in close agreement with the hypothesis.

Postnatal growth and organ development in the quail (Coturnix coturnix Japonica).

In a previous study it has been shown that the pattern of organ growth of the goose, a species with a high growth rate factor, is characterized by a rapid early development of the digestive organs and the liver. The present study describes the postnatal growth and the pattern of organ development of the quail, a species with a low growth rate factor. The results show that the pattern of organ growth is characterized by a rapid early development of the wings, pectorals and feathers. These results support the hypothesis that the rate of which growth proceeds is at least partly determined by the distribution of growth between different organs.

Postnatal growth and organ development in the goose (Anser anser).

A hypothesis has been formulated stating that the rate at which growth proceeds is at least partly determined by the distribution of growth between different organs. In order to test the hypothesis a series of studies of organ growth has been undertaken in some birds with widely ranging growth rate factors. This study describes the postnatal growth and the pattern of organ development of the goose, a species with a high growth rate factor. The results show that the pattern of organ growth is characterized by an early development of the digestive organs and the liver and by a late development of the wings, pectorals and feathers. These results are in close agreement with the hypothesis.