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

The pathogenesis of NC in VLBW infants appears to be multifactorial. The vulnerability of extreme immaturity and the underdevelopment of renal function may be the most important variables. In some ways, we view this problem as similar to that of retinopathy of prematurity. (Clearly the exposure of the retina to high partial pressures of oxygen contributes to the development of retinopathy of prematurity but other variables--some known, such as an immature retina, and others not yet defined--must be present.) Hypercalciuria is common in the VLBW infant, yet not all develop NC. Decreased glomerular filtration rate, low citrate excretion, and frequently an alkaline urine are in part due to the immaturity of renal function of these infants. The need for prolonged hyperalimentation resulting in increased oxalate excretion and the development of BPD frequently requiring diuretics that may cause phosphaturia and magnesium depletion and that may increase calcium excretion are more common in the smallest and sickest of premature infants. Even transient insults to the kidneys, such as hypoxia or hypotension or the use of nephrotoxic drugs that provoke tubular injury and cell death with the probability of crystal formation and growth by way of heterogeneous nucleation, are likely to occur more frequently in this vulnerable population.
 ...
PMID:Nephrocalcinosis. 157 67

Microautoradiographic techniques were used to determine the distribution of Ca(45) and S(35) in regions of the bean root where anatomical features may influence the processes of ion uptake and translocation. Root tissue from intact plants was prepared by methods that preserve both soluble and insoluble Ca and S. Ca(45) distribution was determined after 1 hour and 15 min, of uptake, after 2 efflux periods, and after replacement by non-tracer Ca.S(35) distribution was determined after 1 hour and 15 min of uptake.The quantity of Ca(45) that entered the root was greater than the quantity of S(35). Ca(45) concentration within the root increased with linear distance from the 8-mm level behind the tip. The pathways of Ca and S across the cortex appeared to be different since Ca(45) was particularly associated with cell walls and S(35) was distributed more evenly through the cells. There was no evidence that the endodermis was a diffusion barrier for Ca; the small parenchyma cells associated with conducting elements acquired a high concentration of Ca(45) and thus appear to be implicated in absorption and perhaps in transfer to the xylem. The evidence suggests that the endodermis may have been a barrier for S, but if so, certain parenchyma cells inside the stele, especially at xylem poles, were equally involved. The region from 30 to 80 mm from the tip appeared to participate in Ca uptake and transfer to the xylem; because of tissue immaturity the 8-mm region, which contained the least Ca(45), was thought not to translocate to the shoot. Deposition of Ca(45) in oxalate crystals represented almost complete immobilization. Calcium oxalate metabolism was most active in the 30-mm region of secondary roots and in their small branches. S(35)-labelled nuclei occurred in the cortex 2.5 to 3 mm behind the root tip.
...
PMID:A microautoradiographic study of Ca(45) and S (35) distribution in the intact bean root. 2454 79