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)

The concentrations of aldosterone in the plasma and adrenal glands, the concentrations of sodium and potassium in the plasma and the hematocrit were estimated from birth to day 6 after birth in premature mice removed by Caesarean section on day 19 of pregnancy in comparison with newborn mice delivered spontaneously vaginally on day 20 of pregnancy. In premature mice, the plasma aldosterone concentrations increased twice: at birth after reanimation, then at 6 h after birth. The first increase at birth resulted probably from ACTH stimulation. Several factors could be involved in the peak at 6 h after birth: ACTH stimulation, the decrease in the level of sodium in the plasma and the increase in the hematocrit due to kidney immaturity of premature mice. The results suggest that the renin-angiotensin-aldosterone system is able to respond to stimulations in the first 6 h after birth in premature mice. The rise in the level of plasma aldosterone which has been found at birth in newborns delivered spontaneously vaginally on day 20 of pregnancy (control animals) did not result from variations of plasma electrolytes, plasma volume and ACTH; this rise has been induced by labor of the parturition which caused the aldosterone release from adrenal glands.
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PMID:Plasma and adrenal aldosterone levels in premature mice at birth and during neonatal development. 718 5

Renal handling of magnesium (Mg) has not been comprehensively studied in the newborn period due to the difficulty, until recently, of measuring the diffusible fraction of plasma Mg (UfMg). In the present study this methodology was used to assess Mg homeostasis in 84 newborn infants of different postconceptional age (26-42 weeks), weight (720-4,830 g) and postnatal age (1-72 days). Very premature infants (postconceptional age less than 35 weeks) had significantly higher values of plasma Mg than mature newborn infants. Plasma Mg related inversely to postconceptional age, weight, plasma total protein and plasma calcium, and directly to plasma potassium. Stepwise multiple regression analysis revealed that postconceptional age was the unique factor contributing to variations in plasma Mg. Plasma values of UfMg were the same in preterm as in term infants but, when expressed as a fraction of total plasma Mg (UfMg/Mg), they were significantly lower in very preterm infants. Fractional excretion of Mg and the ratio of urine Mg to urine creatinine did not vary as a function of postconceptional age. These results indicate that plasma UfMg is kept constant at different gestational ages despite variations in total plasma Mg; furthermore, no functional immaturity is present for renal tubular reabsorption of Mg, even in very low birth weight infants.
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PMID:Magnesium homeostasis in premature and full-term neonates. 757 1

Delayed gastric emptying is a common problem in preterm infants. The factors underlying this gastroparesis remain unsettled but may involve immaturity of smooth muscle contraction. The present study was designed to test this hypothesis. Muscle strips from the gastric fundus of fetal and adult guinea pigs were studied in vitro for their contractile response to receptor activation (acetylcholine and bethanechol) and membrane depolarization (potassium chloride). The dose-response curves were analyzed for differences in active force development (kg/cm2). The role of extracellular calcium (Ca2+) in the contractile responses was determined by contracting the tissues in a zero-Ca2+ physiologic saline solution and in the presence of nifedipine, a voltage-dependent Ca2+ channel blocker. The results demonstrate the following: 1) tissues from adult animals developed significantly more active force when tested with acetylcholine, bethanechol, and potassium chloride; 2) tissues from the fetal animals were relatively unresponsive to contraction with potassium chloride compared with the adult; and 3) both nifedipine and incubation in a zero-Ca2+ physiologic saline solution had a significantly greater inhibitory effect on the contractions of adult than fetal muscle strips. Our data indicate that smooth muscle in the gastric fundus develops increasing force with maturation. The increased contractility in the adult fundus appears to be due to an increased involvement of extracellular calcium influx, in part through voltage-dependent Ca2+ channels.
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PMID:Developmental changes in gastric fundus smooth muscle contractility and involvement of extracellular calcium in fetal and adult guinea pigs. 787 85

The mature, fully differentiated connecting tubule (CNT) cell plays an important role in the regulation of serum potassium levels and synthesizes the enzyme tissue kallikrein, a main component of a renal vasoactive system, the kallikrein-kinin system. To characterize the growth of CNT cells (tissue kallikrein-producing cells), we studied the rat kidney at three different time points of postnatal development: at day 5, day 15, and day 30. The CNT cells were identified on tissue sections by a standardized immunohistochemical procedure. The tissue kallikrein content was determined by radioimmunoassay and the activity of the enzyme in kidney homogenates was measured using a selective synthetic substrate. The number of immunolabeled CNT and CNT cells per cortex area gradually increased from day 5 to day 30. A similar rise in the content and activity of tissue kallikrein was observed when the enzyme levels were determined by radioimmunoassay or by the enzymatic method. In addition, the morphometric analysis showed that the distal end of CNT had larger cells that displayed a more intense tissue kallikrein staining than those present in the proximal end, suggesting that the postnatal development of CNT is induced from its juxtamedullary portion. Our results show that tissue kallikrein expression is very low in the newborn rat, increasing gradually with age to reach adult levels at day 30. This finding, together with the morphometric data, suggests immaturity of CNT cells in newborn rats, a fact that could contribute to explaining the high serum potassium levels reported at this stage. In addition, the contrasting behavior of kallikrein and renin in the postnatal development (kallikrein increasing and renin decreasing) could explain the gradual decrease in renal vascular resistance and increase in renal blood flow observed after birth.
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PMID:Postnatal maturation of tissue kallikrein-producing cells (connecting tubule cells) in the rat kidney: a morphometric and immunohistochemical study. 854 32

In a comparative study of the lactational performance of 11 adolescent and 11 adult breast-feeding mothers from the US, adolescents were found to produce significantly less milk and lactate for a significantly shorter period of time than their adult counterparts. All subjects were assessed at 6-24 weeks postpartum. The adolescents produced 37% and 54% less milk at 6 and 24 weeks postpartum, respectively, than adult women. These differences in milk production were significant even when adjusted for differences in the frequency and duration of breast feeding episodes and use of supplementary feeds. The amount of dietary energy the infants of adolescents received from human milk alone was clearly inadequate, at every time point, to support normal growth rates. In both groups, the average frequency of nursing episodes during the first 12 weeks postpartum was 7 or more per 24 hours (consistent with current recommendations for adequate lactation); adolescents, however, spent significantly less time nursing and provided greater quantities of supplementary feeds. While all adult women breast-fed throughout the study period, 20% of adolescents had stopped breast feeding by 12 weeks, 50% weaned by 18 weeks, and 64% had discontinued breast feeding by 24 weeks. Unexpectedly, the energy, lactose, fat, total nitrogen, protein nitrogen, nonprotein nitrogen, sodium, potassium, calcium, and phosphorous concentrations showed little difference between the two age groups. The absence of data from the first 6 weeks of life makes it impossible to rule out a role for early formula supplementation in the decreased milk production of adolescents. It is believed,however, that adolescents may be biologically incapable of producing a full complement of milk because of their developmental immaturity.
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PMID:Lactational performance of adolescent mothers shows preliminary differences from that of adult women. 917 81

Potassium is the most abundant intracellular cation and plays an important role in a variety of cell functions. Potassium regulation and homeostasis during infancy are, owing to growth and development, different from in later life: infants need to retain more K+ than adults, to avoid growth retardation. Since the K+ requirements are different in infants and in adults, the mechanisms regulating K+ homeostasis also need to be different. This paper includes a review of the literature concerning the regulation of internal and external K+ balances during ontogeny. We examined the role of gastrointestinal tract, kidney and some tissue stores in K+ excretion and distribution during development. We conclude that positive K+ balance in infancy is characterized by higher K+ absorption in gut, lower K+ secretion/excretion in kidney and immaturity of the mechanisms regulating intra/extracellular K+ distribution. Several factors contribute to maintain the positive K+ balance. They include higher expression of absorptive transporters in colon and probably in kidney, lower expression of secretive transporters in colon and kidney, lower renal K+ excretion following K+ loading, immaturity of hepato-renal K+ reflex mechanism, immaturity of tissue K+ binding/releasing capacity and immaturity of the neuro-hormonal control of K+ transport in several organs.
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PMID:Potassium homeostasis: ontogenic aspects. 968 50

To determine the postnatal changes in mineralocorticoid action on the cortical distal nephron in preterm neonates, we evaluated the transtubular potassium gradient (TTKG) and its relationship to other renal and non-renal parameters in 16 preterm neonates during the first 5 weeks of life. Preterm neonates were divided into two groups according to their gestational age: the first group (group A, n=9) had a gestational age less than 30 weeks and the second group (group B, n=7) had a gestational age over 30 weeks. TTKG in both groups increased significantly with postnatal age, and TTKG in group A was significantly lower than that in group B (P=0.0003; two-way repeated analysis of variance). TTKG in group A was significantly lower during the 2 weeks of postnatal life than that in full-term neonates [TTKG during 1st week (mean+/-SD) 3.73+/-1.32, P<0.00001; during 2nd week 7.77+/-3.60, P=0.0096 versus full-term neonates (n=19); 11.56+/-3.23]. TTKG in group B was significantly lower only during the 1st week of life (6.55+/-2.71, P=0.0013) compared with full-term neonates. Plasma aldosterone concentration did not correlate with TTKG value. Stepwise regression analysis showed that postnatal age, cortical lumen sodium concentration (CLNa), and clinical condition requiring the use of mechanical ventilation were independent variables that correlated significantly with TTKG. We postulate that the low TTKG level in preterm neonates might reflect the prematurity of renal function (early postnatal age, CLNa) and the condition(s), relating to immaturity, such as the use of mechanical ventilation.
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PMID:Transtubular potassium concentration gradient in preterm neonates. 1060 41

Hypoglycemic episodes occurring during the newborn period are often due to transient immaturity of glucoregulatory pathways. Normal feeding is generally the only measure required to treat such episodes. After the first few hours of life, however, hyperinsulinism (HI) is the most common cause of neonatal hypoglycemia. HI may persist for the first weeks/months of life and then remit spontaneously, particularly in low birth weight neonates and those exposed to perinatal stresses; hypoglycemia in such infants can nearly always be medically controlled using diazoxide. There are also several forms of congenital hyperinsulinism presenting with hypoglycemia in neonates that does not remit. Depending on the type of genetic mutation, hypoglycemia in these infants with congenital hyperinsulinism may be controlled medically or may require surgery. The extent of surgery required in infants with ATP-dependent potassium channel mutations unresponsive to diazoxide is dependent upon histological subtype: focal vs. diffuse disease. Disease-specific diagnoses and treatments are therefore essential for effective management of the various forms of neonatal hyperinsulinism.
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PMID:Hypoglycemia in the neonate. 1726 74

Patent ductus arteriosus (PDA) complicates the hospital course of premature infants. Impaired oxygen (O2)-induced vasoconstriction in preterm ductus arteriosus (DA) contributes to PDA and results, in part, from decreased function/expression of O2-sensitive, voltage-gated potassium channels (Kv) in DA smooth muscle cells (DASMCs). This paradigm suggests that activation of the voltage-sensitive L-type calcium channels (CaL), which increases cytosolic calcium ([Ca2+]i), is a passive consequence of membrane depolarization. However, effective Kv gene transfer only partially matures O2 responsiveness in preterm DA. Thus, we hypothesized that CaL are directly O2 sensitive and that immaturity of CaL function in preterm DA contributes to impaired O2 constriction. We show that preterm rabbit DA rings have reduced O2- and 4-aminopyridine (Kv blocker)-induced constriction. Preterm rabbit DASMCs have reduced O2-induced whole-cell calcium current (ICa) and [Ca2+]i. BAY K8644, a CaL activator, increased O2 constriction, ICa, and [Ca]i in preterm DASMCs to levels seen at term but had no effect on human and rabbit term DA. Preterm rabbit DAs have decreased gamma and increased alpha subunit protein expression. We conclude that the CaL in term rabbit and human DASMCs is directly O2 sensitive. Functional immaturity of CaL O2 sensitivity contributes to impaired O2 constriction in premature DA and can be reversed by BAY K8644.
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PMID:Developmental absence of the O2 sensitivity of L-type calcium channels in preterm ductus arteriosus smooth muscle cells impairs O2 constriction contributing to patent ductus arteriosus. 1809 58

Nutritional insufficiency, leading to early growth deficits has long-lasting effects, including short stature and poor neurodevelopmental outcomes. Early enteral feeding is commonly limited by immaturity of gastrointestinal motor function in preterm neonates. To ensure that a stressed premature infant receives an adequate but not excessive amount of glucose, the amount of carbohydrate delivered in the form of dextrose is commonly initiated at the endogenous hepatic glucose production and utilization rate of 4 to 6 mg/kg/min; and 8 to 10 mg/kg/min in ELBW infants. The early provision of protein is critical to attain positive nitrogen balance and accretion as premature babies lose approximately 1% of their protein stores daily. Aminoacid can be used at concentrations of 3-3.5 g/kg/day and lipid at 3.5-4 g/kg/day as long as the fat intake remains less than 60% of nonprotein calories. Sodium, potassium, chloride, calcium, magnesium and phosphorus need to be provided in PN solution as per their daily needs. Hospital-acquired infection (HAI) is a major complication of PN. All efforts should be made to avoid it.
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PMID:Parenteral nutrition. 1853 94


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