We have examined the independent and combined effects of thyroxine (T4) and bovine growth hormone (bGH) on postweaning growth, satellite cell proliferation and accumulation of myonuclei in extensor digitorum longus (EDL) muscles in rats. Daily subcutaneous injections of T4 (1.5 micrograms/100 g BW), but not bGH (.25 IU/100 g BW) or T4 + bGH, resulted in elevated incidence of satellite cell nuclei and satellite cells per muscle fiber in transverse thin section, and a significantly (p less than .05) higher percentage of satellite cell nuclei and percentage satellite cells as a percentage of all muscle nuclei in transverse thin sections after one week of injections. The higher incidence of myonuclei per muscle fiber in transverse section in T4 injected rats at the end of the injection period (p less than .05) was interpreted to be the result of a higher concentration of satellite cells exhibiting normal or elevated mitotic activity during the early part of the injection period. The higher incidence of myonuclei per fiber was not caused by an increased mean fiber cross-sectional area in T4 injected rats. These histological observations relative to T4 injections were not accompanied by significantly greater weight, DNA content or estimates of total satellite cells per EDL muscle after either one or three weeks of hormone injections. These studies support the premise that T4 may be directly involved in the regulation of satellite cell proliferation and myonuclei accumulation, however, they do not support the premise that growth hormone exerts a similar influence during early muscle growth and development.

The manner and rate of nuclear proliferation and accumulation in rat skeletal muscle was investigated using a model of induced permanent growth impairment in rats to gain additional insight into the regulation of skeletal muscle growth. Comparisons were made at 1, 21 and 175 d between control progeny and progeny of dams restricted during gestation and lactation to 50% the daily feed intake of ad libitum fed controls, followed by realimentation after weaning. Estimates of total satellite cells/muscle were lower (P less than .01) in soleus and extensor digitorum longus (EDL) of restricted progeny at 21 and 175 d. Estimates of total satellite cells/muscle increased nearly twofold between 21 and 175 d in the soleus and decreased slightly in EDL in both treatment groups. Satellite cell concentration expressed as a percentage of total muscle nuclei was not different between restricted and control progeny at either 1 or 175 d. However, while satellite cell percentages decreased about 50% between 1 and 21 d in controls, they remained at initial levels in restricted progeny. Incidence of satellite cells/muscle fiber (satellite cell concentration) decreased between 1 and 21 d in control soleus and EDL, but remained unchanged or was slightly higher in soleus and EDL of restricted progeny at 21 d. Incidence of satellite cells continued to decrease between 21 and 175 d in restricted and control EDL and restricted soleus, but was unchanged in control soleus. Incidence of myonuclei/fiber (myonuclei concentration) increased with age (P less than .005), was not affected by growth impairment either before or after realimentation and was higher (P less than .005) in soleus than EDL.(ABSTRACT TRUNCATED AT 250 WORDS)

ABSTRACTPrecooked, frozen omelets were analyzed for moisture loss, expressible moisture, shear‐force, and sensory evaluation to determine water‐holding capacity and‐ textural acceptability. Addition of 0.1% xanthan gum, application of moist heat in cooking, and cryogenic freezing with liquid carbon dioxide or nitrogen minimized moisture loss and shear force. Sodium. carboxymethylcellulose (CMC), pre‐gelatinized tapioca starch and sodium tripolyphosphate additives performed satisfactorily, but omelets containing xanthan gum were consistently rated highest in sensory evaluation of several treatments, including fresh and untreated control omelets. Steaming omelets for five minutes combined with cryogenic freezing produced a desirable‐ omelet, requiring no additives. Steamed omelets were rated comparable to baked omelets in most sensory parameters.