Growth control of the rat skull. Differential effects of undernourishment and of altered behaviour in experimental bipedia.
Experimental bipedia results in retarded general development and in a change of skull form. The present study was undertaken to investigate the precise cause(s) of the changes of skull growth. Skull growth was restudied in experimentally bipedal male rats and compared to that in control rats that were reared in extra large litters, thereby creating undernutrition during the pre-weaning period. In addition, another category of control rats were reared in litters of standard size. The animals were sacrificed at the age of either 30 or 46 weeks. The following observations were made. In bipedal as well as in large-litter rats the cranial base was different to that of the standard-litter rats with respect to the following aspects: the basisphenoid bone was reduced in length, and the cranial base was more dorsally flexed at the spheno-occipital synchondrosis. Both differences, therefore, do not seem to be specific for the bipedal condition, but must be the consequence of general growth retardation during early life. The supra-occipital bone, on the other hand, was rotated backward in the large-litter rats, but rotated forward in the bipedal rats. This phenomenon seems to be the only change observed so far that is specific for the bipedal condition.
D000671:Amputation, Surgical / Q000662:veterinary; D000818:Animals; D001522:Behavior, Animal; D001835:Body Weight; D002508:Cephalometry; D005260:Female; D005508:Food Deprivation; D005552:Forelimb / Q000601:surgery; D008098:Litter Size; D008297:Male; D011247:Pregnancy; D051381:Rats / Q000033:anatomy & histology / Q000254:growth & development*; D011919:Rats, Inbred Strains; D012886:Skull / Q000033:anatomy & histology / Q000254:growth & development*