INCREASED NUMBERS OF ANNULATE LAMELLAE IN MYOCARDIUM OF CHICK EMBRYOS INCUBATED AT ABNORMAL TEMPERATURES

Abstract

Annu-late lamellae have been observed in the myocardium of 18-day-old chick embryos maintained at the normal temperature of 100[degree] F and at 90[degree] F during the last week of incubation. An increased number of annulate lamellae was observed in heart muscle of embryos incubated at 90[degree]F. This is probably caused by a persistent production of these organelles, since annulate lamellae are present in greater fre- quency than in 11-day-old embryos incubated at 100[degree]F. In the hyper-trophic hearts of 18-day-old embryos incubated at 90[degree]F, the annulate lamellae were associated with a net increase of protein content and an elevated concentration of myocardial glycogen. It is suggested that the increased number of annulate lamellae is a sequela of reduced environmental temperature during incubation.