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 glutathione S-transferases of human fetal and neonatal liver catalyse the conjugation of glutathione with chloramphenicol at a low but measurable rate. The highest rates were 1.30 nmol/min/mg protein in a preterm neonate of 26 weeks of gestation and 1.11 nmol/min/mg in a fetus of 22 weeks of gestation, while the lowest measurable was 0.1 nmol/min/mg in a fetus of 17 weeks of gestation. The activity did not correlate with gestational age, but appeared dependent on the concentration of glutathione in the reaction mixture. The rate rose by a factor of three, from 0.39 nmol/min/mg protein with no added glutathione to 1.24 nmol/min/mg with 2 mumol/ml added to the reaction mixture. Chloramphenicol-aldehyde was detectable in the reaction mixture when a liver extract was incubated with glutathione but the proposed intermediate, glutathione-chloramphenicol, could not be demonstrated. Differences in activity with chloramphenicol or a model substrate, under varying conditions, indicate that different isoenzymes are concerned with the conjugation of glutathione to the two substrates. These data support the hypothesis that when glucuronide conjugation is depressed by immaturity, chloramphenicol is metabolised via other pathways.
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PMID:Metabolism of chloramphenicol by glutathione S-transferase in human fetal and neonatal liver. 764 46

In this study, we present a novel guided bone regeneration (GBR) concept that consists of combining Boneject, a bone substitute containing atelocollagen and bovine hydroxyapatite particles, with thermoplastic, bioresorbable plates (DeltaSystem) known to resist mechanical loading. In rat calvariae, standardized bone defects were filled with Boneject and covered with a convex DeltaSystem plate. Tissue from rats at 1, 2, 4, 8, and 12 weeks postoperation were fixed with an aldehyde solution, and the new bone formed at the defects was histologically assessed. At 1 week, alkaline phosphatase (ALP)-negative cells deriving from the bottom region of the defect could be found up to half the height of the cavity. Boneject particle surfaces in the bottom region revealed an intense osteopontin immunopositivity whereas those in the upper region did not. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts accumulated on the surfaces of osteopontin-coated particles. A newly formed, woven-like bone featuring ALP-positive osteoblasts extended from the native bone. At the second week, the newly formed woven bone had surrounded the Boneject particles. Cement lines, which indicate active bone remodeling, could be observed in the new bone despite its immaturity. Four weeks after surgery, the new bone had reached the height of the DeltaSystem plate, and just beneath it a periostin-positive fibrous layer covered the mix of new bone and Boneject particles. By then, despite having acceptable histological features, electron probe microanalyzer (EPMA) and transmission electron microscope (TEM) analyses revealed that the new bone could not be regarded as compact bone. At 8 and 12 weeks, the new bone showed compact bone-like features according to TEM and EPMA assessments. Summarizing, the combination of a bone substitute such as Boneject and a rigid, bioresorbable plate appears to be osteoconductive and to promote bone remodeling, leading to the genesis of a tissue similar to the one that is regarded as the "gold standard" for bone regeneration: the compact bone.
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PMID:Histological examination of bone regeneration achieved by combining grafting with hydroxyapatite and thermoplastic bioresorbable plates. 1796 88