Topic
Alkaline phosphatase
About: Alkaline phosphatase is a research topic. Over the lifetime, 20218 publications have been published within this topic receiving 540547 citations. The topic is also known as: Alkaline_phosphatase & IPR001952.
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TL;DR: Using cells obtained by sequential enzyme release from fetal rat parietal bone, TNF alpha is found to inhibit collagen synthesis and alkaline phosphatase activity in osteoblast-enriched cell cultures by mechanisms that are not related to its effects on cell replication.
Abstract: Tumor necrosis factor-alpha (TNF alpha), a product of activated monocytes, induces tissue wasting in certain solid tumors in vivo and in in vitro model systems. Recent studies indicate that TNF alpha also regulates cell replication and expression of differentiated function in a variety of nonneoplastic cell systems. Since monocyte products could accumulate in bone with trauma, inflammation, or other disease states, bone cell activity might be altered by the presence of these pathophysiological molecules. Using cells obtained by sequential enzyme release from fetal rat parietal bone, we find that TNF alpha has acute stimulatory and inhibitory effects on bone cell macromolecular synthesis. Within 24 h of exposure, recombinant human TNF alpha at 0.3-100 nM progressively increases the rate of DNA synthesis in osteoblast-enriched cell cultures up to 3- to 4-fold, and 3-100 nM TNF alpha reduces collagen production and alkaline phosphatase activity by 20-30%. These decreases are not altered by 1 mM hydroxyurea, which blocks the mitogenic effect of TNF alpha by 85-90%. In addition, hydroxyproline levels in the culture medium do not increase relative to the control value after TNF alpha treatment, suggesting that decreased collagen production results from less synthesis rather than increased collagen degradation. Hybridization studies with cDNA encoding the alpha 1-chain of rat type I collagen show that TNF alpha increases type I collagen mRNA to an extent similar to its effect on cell replication. Therefore, TNF alpha appears to inhibit collagen synthesis and alkaline phosphatase activity in osteoblast-enriched cell cultures by mechanisms that are not related to its effects on cell replication.
121 citations
TL;DR: Observations support a glial influence on enzyme activity at the blood-brain barrier by showing membrane-associated reaction product on the cerebral endothelial cell for both Na+,K+-ATPase and non-specific alkaline phosphatase was markedly increased when the endothelial cells were co-cultured with glial cells.
121 citations
TL;DR: Insight is provided into their evolutionary history and the mechanisms of catalysis and of uncompetitive inhibition, and there is reason to suggest that the enzyme may serve to guide migratory cells and to transport specific molecules across membranes.
Abstract: The current information on the cloning and sequencing of four alkaline phosphatase genes (PLAP, GCAP, LAP, TNAP) has been reviewed. It has provided insights into their evolutionary history and the mechanisms of catalysis and of uncompetitive inhibition. The oncodevelopmental biology of the germ cell and its excessive GCAP eutopic expression in neoplasia are noted, and there is reason to suggest that the enzyme may serve to guide migratory cells and to transport specific molecules such as fat and immunoglobulins across membranes. The hyperexpression of all four genes has been observed in various human tumors and in their cell lines, particularly cancers of the testis and ovary. The membrane APs have been investigated as targets for immunolocalization and immunotherapy.
121 citations
TL;DR: It is suggested that Ca2+ in Ca(OH)2 specifically modulates osteopontin and BMP-2 levels during calcification in pulp during serum-free conditions.
120 citations
TL;DR: Results from DBM batches, originating from five established Bone Banks, showed good consistency between in vitro and in vivo assays, however, DBM activity varied widely from bank to bank as well as from batch to batch within the same bank.
120 citations