Improving global integration of crop research

Field laboratories in realistic crop environments are needed

Vascular-induced intrauterine growth retardation: relations between birth weight and the development of biochemical parameters in young rabbits

The development of biochemical parameters (cellular DNA and protein) in relation to birth weight was studied in the rabbit, a perinatal brain developer. To induce intrauterine growth retardation and to increase the number of low-birth-weight rabbits, experimental ischemia, in half the fetuses of each doe, was achieved by total ligation of approximately 30% of uteroplacental vessels during the last third of gestation. Following natural delivery, the rabbit pups were raised until 60 days of age, at which time the brains were removed and dissected into cerebral hemispheres, cerebellum and brain stem. The amount of DNA (representing cell number) and protein (suggesting cell size) was estimated in each brain region. A significant correlation was found between low birth weight and reduced DNA in the cerebellum and reduced protein in the cerebral hemispheres. These persistent deficiencies could be related to some lasting handicaps, especially motor incoordination, as an expression of cerebellar dysfunction.

Relations between birth weight and learning ability in young rabbits

Performance on visual discrimination learning was studied in 41 rabbit pups mainly in relation to their birth weight, but also as functions of their neonatal motor development and weight gain between birth and training time. Partial placental vascular ligation was performed on some fetuses to increase the number of small-for-gestational-age pups. No relation was found between learning ability and either birth weight or rate of motor development. Low birth weight showed some association with slightly delayed motor development, but resulted in no lasting motor handicap. Between two subgroups of low birth weight pups, those who showed substantial weight gain by training time learned faster than those who remained relatively small.