ABSTRACT
An analysis of the gross composition of milk in five inbred strains of mice (NZB, CBA/H, BALB/c, C57BL/6, XLII) was conducted for two different days during the lactating period (6th and 9th day after parturition). The quantity of milk and the concentration of proteins, lactose and lipids were measured. Results show a significant effect for day on the quantity of milk, but not for strain. Day effect was also observed for proteins and lactose; however modifications in the concentration of lactose and lipids from the 6th to the 9th day were not identical across strains. Also, a strain effect was present for proteins, lipids and lactose.
Subject(s)
Milk/analysis , Species Specificity , Animals , Female , Lactose/analysis , Lipids/analysis , Mice , Mice, Inbred Strains , Milk Proteins/analysis , PregnancyABSTRACT
A simple method of milk extraction in mice requiring only a brief isolation period is presented. This method has two main advantages in that the amount of milk obtained at the 6th and the 9th day of lactation is sufficient for biochemical analysis of the major components (proteins, lactose and lipids), and it can be used on primiparous females from inbred strains who are known to produce small quantities of milk. Results show that amount of extracted milk and weight of the pups are related.
Subject(s)
Lactation , Milk Ejection , Animals , Female , Lactation/drug effects , Mice , Mice, Inbred Strains , Milk Ejection/drug effects , Oxytocin/pharmacology , PregnancyABSTRACT
The genetic and environmental bases for differences in rate of development were investigated in 2 inbred strains of mice: C57BL/6By (B) and BALB/cBy (C). Twelve motor responses, aside from individual weight, were used to measure these differences. The Recombinant Inbred Strains method was chosen to perform the genetic analysis. Overdominance is shown to be present in 2 variables alone (eye opening, weight at 10 and 20 days). In most cases, each of the response reflexes was found to be associated with several genes (locomotion, hind limb, crossed extensor, righting, vibrissae placing, bar holding). Differences across strains are associated with one segregating unit for rate of disappearance of the rooting response. This unit is mapped on the part of the 4th chromosome including the loci b and H-21. The strain distribution pattern differs for each sensory motor response, consequently no one general genetic factor of development can be advanced. Maternal effects were found for 4 variables (grasping, fore limb placing, eye opening and weight). For two responses, the F1 pups developing the fastest were reared by mothers from the slowest developing parental strain. As regards this latter finding, the authors hypothesize that mothers differ as to the quality of the environment they furnish to their young and pups differ in their ability to benefit from these environments.
