English Abstract
ABSTRACT :
The study is concerned with the effects of temperature on mammalian bone growth. The tail bones of the mouse were used because they tend to assume the environmental temperature at which the animals are maintained. Thus the tail vertebrae cf 25 day old mice grow very slowly when the animals are placed in a cold environment (8°C), but when the animals are placed in a hot environment (33°C) the vertebral growth rate increases approximately four-fold. The change in growth rate appears to be immediate and certainly occurs in less than 2 hours and this may indicate the role of the differentiated cartilage cells in bone growth. High dose irradiation (5000 r) given to the 32 day old "cold tails" prior to being placed in the hot room does not alter the initial acceleration of growth during the first 12 hours but no growth occurs after this period. Increased growth rate after 12 hours in the un-irradiated tails is due to mitotic activity of the generative cartilage cells of the growth plates.
The growth of long bones is controlled by local mechanisms. Thus bones inside the body, including some of the proximal tail bones, are little affected by changes in environmental temperature.
The distal tail vertebrae of mice kept in the hot environment complete their development and cease growth earlier than those animals kept at lower temperatures. The tails of animals kept at 8°C continue to grow very slowly for many months although in central parts bone growth is completed normally. If these "cold animals" are placed in the hot environment at any time up to 310 days there is a spurt of growth but the final length never equals that of the animals kept constantly in the hot environment。
