Changes in skin blood flow over the foot with warming of the contralateral heel

Vasospasm in one leg is a common complication of umbilical artery catheterization in preterm infants. It is a common practice to wrap the contralateral leg in a warm washcloth. The rationale for this intervention is to induce reflex vasodilatation of the affected extremity, thereby avoiding the necessity to remove or replace the catheter. This study tested the hypothesis that heating the contralateral extremity in preterm infants would increase peripheral blood flow to the contralateral foot. Ten stable preterm infants who had had no umbilical catheter inserted for at least 2 weeks were studied. Skin perfusion was measured using the laser Doppler method in the distal leg after heating of the opposite foot to 40.5 degrees C. Blood flow to the skin of the contralateral foot was measured before and after warming the ipsilateral one. The skin blood flow measured with and without heat application to the contralateral foot was not significantly different. Direct heat does not induce contralateral reflex vasodilatation in the foot of preterm infants.

Neonatal hyperthyroidism alters hepatic epidermal growth factor receptor ontogeny in mice

Epidermal growth factor (EGF) liver receptor ontogeny and somatic growth were studied in mice from day 7 to day 70 postnatally to assess long-term effects of short-term postnatal thyroxine treatment. The mice were given 0.4 micrograms thyroxine/g body weight/day for the 1st wk of life. EGF receptor binding in liver tissue was studied on days 7, 15, 20, 30, and 70 postnatally. Treated animals had accelerated eyelid opening and tooth eruption, and permanent growth retardation was obvious from the second week of life. Hepatic EGF receptor-binding capacity increased markedly in control mice with increasing age in contrast to a very slow increase in treated mice, making the difference statistically significant (P less than 0.01) from day 30. The affinity of EGF receptor binding initially was similar in the two groups of animals (1.09 x 10(9) M-1 and 1.02 x 10(9) M-1) and increased by day 30 in controls (2.57 x 10(9) M-1), an increase that was not observed in treated animals either at day 30 or 70. These results suggest a sensitive period of imprinting during the first 7 days postnatally, a period when thyroxine can exert a permanent effect on later growth and later hepatic EGF receptor number.

Effect of oestradiol-17 beta on uterine epidermal growth factor concentration in immature mice

Using a specific and sensitive epidermal growth factor radioimmunoassay (EGF-RIA) we have identified EGF in immature mouse uterine tissue. In 16 day old mice a single injection of oestradiol-17 beta (E2) elicited an increase in uterine wet weight in 24 h but did not affect uterine EGF concentration. Sequential injection of E2 for a 7 day period increased both uterine wet weight and EGF concentration suggesting that change in EGF concentration is a delayed E2 response. The continuous treatment did not alter liver or submandibular gland tissue EGF concentrations, but significantly increased kidney EGF content. These data reveal that both uterine and renal tissue EGF concentrations are subject to modulation by E2 in developing mice.

The thyroid hormone effects on growth and development may be mediated by growth factors

Thyroid hormones modulate energy metabolism and importantly influence growth and development. These effects are independently mediated. Thyroid calorigenesis is influenced predominantly via nuclear receptor mediated synthesis of mitochondrial respiratory assemblies and cell membrane sodium potassium ATPase. Accumulating evidence suggests that many of the thyroid hormone effects on development are mediated via growth factors, including somatomedins (SM), erythropoietin (EP), nerve growth factor (NGF) and epidermal growth factor (EGF). Thyroid hormone binding to nuclear receptors is known to stimulate growth hormone (GH) synthesis, and thyroid hormones probably potentiate GH stimulation of SM production as well as the anabolic effects of SM. The production of EP, NGF and EGF also are thyroid hormone responsive, and it seems likely that these growth factors mediate the thyroid hormone effects on erythrocyte production, autonomic and perhaps central nervous system maturation, and epidermal development, respectively.