Unweaned Rats Research Articles

The absorption of (58Co)cyanocobalamin by unweaned rats.

1. ‘58Co’cyanocobalamin was given by stomach tube to Wistar albino rats aged between 6 h and 24 days. The fraction of the dose absorbed was assessed by measuring the amount retained by the animals after 7 days, by total body counting.2. Rats up to 4 days old absorbed about 90% of the test dose, compared with a mean of 83% at the age of 8 days, 66% at 16 days and 47% at 24 days.3. The proportion of the test dose absorbed did not appear to be affected by starvation for up to 24 h, by increasing the dose from 0·05 ng to 0·25 ng/g body-weight, or by giving the ‘58Co’cyanocobalamin mixed with rat's milk.4. The results support earlier suggestions that newborn rats absorb vitamin B12 by a different mechanism from that in adults.

A new method of isolating and counting Nippostrongylus brasiliensis from unweaned rats.

METHODS for the recovery and counting of adult Nippostrongylus brasiliensis from the intestines of adult rats have been described by Jennings et al.1 and Ogilvie2. Such methods need to be very accurate, particularly where estimations of the degree of immunity of the host are to be made on the basis of such counts. The techniques described by these authors have been used routinely in this laboratory during experiments on adult rats and have proved quite satisfactory. However, on application to the recovery of worms from the intestines of neonatal or unweaned rats a number of difficulties were encountered.

The toxicity of morphine to fully grown and unweaned rats by constant intravenous infusion.

The toxicity of morphine to fully grown and unweaned rats by constant intravenous infusion.

Contribution of histamine and enteramine (5-hydroxytryptamine) to the selfdepression in subcutaneous absorption of morphine by fully grown and unweaned rats.

Contribution of histamine and enteramine (5-hydroxytryptamine) to the selfdepression in subcutaneous absorption of morphine by fully grown and unweaned rats.