Morphological and metabolic responses of embryonic hearts to administration of exogenous L-thyroxine.

Injection of 1 microgram L-thyroxine (T4) into the yolk sacs of embryonated chicken eggs at 3 to 6 days of incubation not only induced cardiomegaly but also instigated more rapid differentiation of the heart as an organ and of the individual myocytes per se. Myocytes showed evidence of responding to this dose of exogenous T4 as early as 5 to 6 days of incubation, even though endogenous T4 was not normally forthcoming (in amounts sufficient to provoke organ changes) until 11 to 12 days of incubation. By 7 days of incubation the hearts, conditioned by a single 1 microgram dose of T4, exhibited larger areas occupied by myofibrillar material than controls.

Effects of chondroitin-4-sulphate on survival, sizes and ultrastructures of cultured WI-38 fibroblasts and fibroblasts from progeria patients.

WI-38 fibroblasts from 'normal' individuals and skin fibroblasts from patients displaying classical symptoms of progeria (accelerated aging) were maintained in tissue culture with and without periodic supplementation of 0.25 mg/ml of chondroitin-4-sulphate (C-4-S) during the ultimate phase of slowed division (phase 3). When C-4-S was not present in the culture medium, cell counts (not necessarily indicative of relative rates of cell division) and mean cell volumes were lower, and intracellular aberrations were higher, in both types of fibroblasts (normal and progeria) at, and even before, the 47th-50th and 13th-16th passages, respectively.

Changes in fatty acid compositions of mitochondria during embryonic development.

1. A general trend among biomembranes of hepatocytes in the developing avian embryo is to display increasing percentages of unsaturated fatty acids, especially oleic acid (C18:1). 2.

The glycosaminoglycan chondroitin-4-sulfate alters progesterone secretion by porcine granulosa cells.

Porcine granulosa cells from small (1-2 mm), medium (3-5 mm), and large (6-12 mm) antral follicles were cultured in monolayer for 2 to 3 days with 0 to 3 mg of chondroitin-4-sulfate (C-4-S)/ml in the presence or absence of 0.5 microgram follicle-stimulating hormone (NIH-FSH-S13)/ml. Testosterone (1.

Effects of thyroxine on mitochondrial morphology and uptake of 35S in embryonic chicken livers.

Ultrastructural analyses of reactions of mitochondria in hepatocytes of chicken embryos to low levels of exogenous thyroxine (T4) reveal that such reactions (overall swelling accompanied by disruption of crest geometry) first take place at about 10 days of incubation, T4 having been administered on the 6th day. Physically altered mitochondria may be seen after 11-12 days of incubation but are no longer evident by 13 days. Correlated with the initial evidence of T4 effects on mitochondria at 10 days of incubation is a spurt in hepatocyte proliferation.