Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029713 (immaturity)
 4,335 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neonatal RBC contain many more spontaneous endocytic vacuoles than do adult RBC. It is not known if this difference is a result of an increase in production of vacuoles in the neonatal RBC (as is the case in drug-induced endocytosis), or is the result of a less effective neonatal macrophagic "pitting" process. Using an in vitro model of spontaneous endocytosis, we compared the rate and quantity of vacuoles and the shape of cord and adult RBC containing pits, visible by interference contrast microscopy (Nomarski method). The mechanism of the spontaneous endocytosis was explored using different inhibitors: sodium vanadate an inhibitor of ATPases, sodium fluoride which inhibits the generation of ATP and sodium cyanide a potent inhibitor of oxidative phosphorylation. We then compared spontaneous endocytosis with two other forms of RBC endocytosis: drug-induced endocytosis and receptor-mediated endocytosis. Spontaneous endocytosis is in fact increased in neonatal RBC initially but the increase in number of RBC containing pits after 144 hr of incubation is almost the same in adult RBC and neonatal RBC. Comparing spontaneous endocytosis with drug-induced endocytosis, it appears that their mechanisms are different in that spontaneous endocytosis is not preceded by stomatocytic shape change and is not inhibited by sodium vanadate or sodium fluoride as is the case for drug-induced endocytosis. Spontaneous endocytosis is different than transferrin receptor-mediated endocytosis because it occurs in many RBC, not only in the motile R1 reticulocytes and is not inhibited by sodium cyanide as is receptor-mediated endocytosis. Thus spontaneous endocytosis appears to be different than drug-induced endocytosis and transferrin receptor-mediated endocytosis. The increase in spontaneous endocytosis in cord RBC seen in vivo is probably a consequence of an immaturity of the neonatal macrophage pitting process.
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PMID:Spontaneous endocytosis in human neonatal and adult red blood cells: comparison to drug-induced endocytosis and to receptor-mediated endocytosis. 202 38

Autonomic regulatory mechanisms and some metabolic functions are predominantly influenced by the sympathetic nervous system. Premature and mature newborns show a high variability and a low adaptability of the sympathetic nervous system. In order to investigate whether sympathetic systems are completely developed at birth or underly a postnatal maturation process we have determined plasma levels of adrenaline and noradrenaline as well as the density and affinity of alpha- and beta-adrenoceptors on thrombocytes and lymphocytes in pre- and mature newborns and adults. Catecholamines were determined by means of a radioenzymatic method, number and affinity of adrenoceptors by use of the radioactive labelled antagonists 3-H-Yohimbine and 125-I-Cyano-Pindolol. Beta-adrenoceptor responsiveness was assessed by measurement of cyclic AMP in lymphocytes before and after stimulation of beta-adrenoceptors by isoprenaline. A linear relationship occurred between the gestational age and the number of adrenoceptors on lymphocytes, whereas the alpha-adrenoceptors on thrombocytes showed no age dependency. The basal content of cyclic AMP and the accumulation in response to beta-adrenoceptor stimulation by isoprenaline was significantly lower in newborns than in adults. Since noradrenaline and adrenaline plasma levels were not significantly different in newborns and adults it is assumed that the low density of beta-adrenoceptors in premature and mature newborns is due to a postnatal maturation and not to a "down regulation" by circulating catecholamines. Our results suggest that an immaturity of beta-adrenoceptors is involved in the poorly developed adaptive control in newborns.
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PMID:[Postnatal development of the sympathoadrenergic system in premature and newborn infants]. 301 54