Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036474 (scurvy)
 685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies suggested that decreased type I collagen synthesis in calvaria of ascorbate-deficient guinea pigs was correlated with weight loss rather than defective proline hydroxylation. The generality of this correlation was examined in articular cartilage, which synthesizes mainly type II collagen, by measuring collagen synthesis and proline hydroxylation in vitro in tissue from ascorbate-supplemented and scorbutic guinea pigs. Ascorbate concentrations in tissues were almost completely depleted after 1 week of deficiency, but proline hydroxylation remained normal until after approximately 3 weeks, when it had decreased only by 10%. At that point collagen synthesis had decreased to about 50% of the control value. There was little additional effect on proline hydroxylation but collagen synthesis decreased further to 20% of normal. Procollagen mRNA levels in cartilage, as measured by dot-blot hybridization with a type II-specific cDNA probe, were unchanged after 2 weeks of scurvy, which correlated with the lack of effect on collagen synthesis during that period. Thereafter, during the period when collagen synthesis decreased, procollagen mRNA levels decreased to 20% of control values. Refeeding ascorbate to acutely scorbutic animals led to reversal of defective proline hydroxylation within 24 h with a slower increase in collagen synthesis and mRNA levels. Collagen synthesis returned to the normal level after 4 days with no further increase, while mRNA levels continued to increase to 2.7 times the control values after 7 days. Thus the major mechanism for regulation of collagen synthesis in articular cartilage during scurvy and ascorbate repletion occurs independently of the effect on proline hydroxylation and is associated with changes in mRNA levels. The lack of precise coordination between collagen synthesis and mRNA levels during repletion, however, suggests that there may be additional regulation through post-transcriptional mechanisms.
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PMID:Regulation of collagen synthesis and mRNA levels in articular cartilage of scorbutic guinea pigs. 396 25

The precise physiological role of alkaline phosphatase is unknown, although evidence suggests it is involved in bone mineralization. Previous studies showed that serum and bone alkaline phosphatase activity is decreased during vitamin C deficiency. Some effects of scurvy, such as inhibition of collagen synthesis, are related to weight loss and subsequent induction of insulin-like growth factor binding proteins and they can be duplicated in fasted guinea pigs receiving vitamin C. We found that decreased alkaline phosphatase activity in bone and serum during scurvy was not completely due to the "fasting effect" and that the decrease in serum was due to loss of bone isoenzyme activity. There also was a decrease in immunoreactive enzyme protein and alkaline phosphatase mRNA concentrations in bone of scorbutic animals, indicating that synthesis of the enzyme was inhibited. Sialylation and addition of the glycosylphosphatidylinositol anchor to the enzyme in bone tissue were not affected by scurvy. The concentration of mRNA for osteocalcin, a bone-specific marker, also fell during scurvy and to a much greater extent than either alkaline phosphatase or type I collagen mRNAs, while osteopontin mRNA concentrations increased. These results differ from the reported role of ascorbic acid on the pattern of expression of these proteins during differentiation of osteoblasts in culture. The decreased expression of collagen, alkaline phosphatase, and osteocalcin could explain the defects in bone caused by scurvy.
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PMID:Regulation and properties of bone alkaline phosphatase during vitamin C deficiency in guinea pigs. 895 Oct 38