Independence of special forms of chlorophyll a and chlorophyll holochromes. Zea mays L. seedlings were cultivated for 10 days with submission to 4 s illumination periods interspersed with dark periods varying in lengt...
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The mode of inhibition of α-1-antitrypsin of chymotrypsin, trypsin and pancreatic elastase was examined by a kinetic method. All three enzymes were completely bound to α-1-antitrypsin;therefore, the dissociation con...
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The VX2 carcinoma produces profound hypercalcemia (17–22 mg 100 ml ) in the rabbit about 3–4 wk after transplantation. A bone resorption-stimulating factor (assayed in vitro with mouse calvaria in culture) has been ...
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The VX2 carcinoma produces profound hypercalcemia (17–22 mg 100 ml ) in the rabbit about 3–4 wk after transplantation. A bone resorption-stimulating factor (assayed in vitro with mouse calvaria in culture) has been extracted with diethyl ether from the tumor tissue and from the medium of a clonal strain of VX2 cells grown in culture. Serologic methods reveal that the tumors contain 294 ± 51 ng/g fresh weight (mean ± SE, 25 tumors) of prostaglandin E2 (PGE2 ), a potent bone resorption-stimulating agent. VX2 cells in culture produce 0.5–3.0 μg PGE2 per mg cell protein per 24 hr. The production of bone resorption-stimulating activity and PGE2 by VX2 cells in culture were both inhibited by indomethacin (100 ng/ml). Tumors from normocalcemic, indomethacin-treated rabbits (10–40/mg rabbit 24 hr) contained little or no bone resorption-stimulating activity nor PGE2 . Tumor-bearing rabbits receiving indomethacin continuously did not develop hypercalcemia; however, following cessation of indomethacin administration, hypercalcemia developed rapidly and was again reversed by reinstitution of indomethacin feeding. In untreated, hypercalcemic, tumor-bearing rabbits, initiation of indomethacin treatment was followed by a rapid return of the plasma calcium to the normal range. Systemic venous plasma from hypercalcemic tumor-bearing rabbits contained higher concentrations of PGE2 than plasma from normocalcemic control rabbits. Venous drainage of the tumor contained even higher plasma PGE2 concentrations than systemic venous plasma in hypercalcemic animals; plasma PGE2 concentrations locally and in systemic plasma were unmeasurable (<70 pg/ml) in normocalcemic, indomethacin-treated, tumor-bearing rabbits. We conclude that PGE2 is a bone resorption-stimulating factor produced by VX2 tumor cells, and that secretion of PGE2 by the tumor in vivo may well be responsible for the hypercalcemia observed in tomor-bearing rabbits.
About 300 single-amino-acid mutations in proteins were compared with the corresponding changes in the amino acid code. Transitional base changes are more common than transversions. Among transitions AG interchanges ar...
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About 300 single-amino-acid mutations in proteins were compared with the corresponding changes in the amino acid code. Transitional base changes are more common than transversions. Among transitions AG interchanges are more common than CU interchanges and AU interchanges are the most infrequent of transversions. Of the 17 undiscovered single-amino-acid mutations, 15 are transversions that do not produce a change in charge.
trace elements, history, tissue content, metabolic functions, sources and absorption, clinical disorders and other effects of deficiencies, and other reviews on I, fe, Zn, Cu, Cr, Co, Mn, Mo, V, Ni, Se, Si, Sn, f
trace elements, history, tissue content, metabolic functions, sources and absorption, clinical disorders and other effects of deficiencies, and other reviews on I, fe, Zn, Cu, Cr, Co, Mn, Mo, V, Ni, Se, Si, Sn, f
Quercetin (3,3′,4′,5,7-pentahydroxyflavone) shares certain properties with the mitochondrial ATPase inhibitor protein. At low concentrations it inhibits both soluble and particulate mitochondrial ATPase and has no e...
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Quercetin (3,3′,4′,5,7-pentahydroxyflavone) shares certain properties with the mitochondrial ATPase inhibitor protein. At low concentrations it inhibits both soluble and particulate mitochondrial ATPase and has no effect on oxidative phosphorylation in submitochondrial particles. Unlike the mitochondrial inhibitor protein quercetin inhibits the ATP-dependent reduction of NAD + by succinate in fully reconstituted submitochondrial particles. A comparison of various flavones indicates that the hydroxyl groups at the 3′ and perhaps 3 position are important for the inhibition of ATPase activity.
1. The reversible equilibrium between the mitochondrial ATPase (f1) and its naturally occurring inhibitor in Mg-ATP submitochondrial particles has been studied under different conditions. 2. High ionic strength favour...
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The sequence of amino acid residues comprising the major form of sheep red cell carbonic anhydrase C has been determined. The primary sequences of peptides derived from cyanogen bromide cleavage and tryptic digestion ...
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The sequence of amino acid residues comprising the major form of sheep red cell carbonic anhydrase C has been determined. The primary sequences of peptides derived from cyanogen bromide cleavage and tryptic digestion were obtained primarily through the use of the Edman degradation procedure. The ordering of these peptides in the sheep molecule is based on the high degree of homology between the sheep enzyme and the previously sequenced human and bovine carbonic anhydrase C molecules. Based on comparisons with the three-dimensional structure of human carbonic anhydrase C, the function of certain residues which appear to be involved either in the maintenance of structure or in the active site of the sheep enzyme is discussed.
Echinococcosis is a disease prevalent both in man and animals with no effective therapeutic measures established against it so far, except for surgical removal of the cyst in humans. Attempts have been made to compare...
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Echinococcosis is a disease prevalent both in man and animals with no effective therapeutic measures established against it so far, except for surgical removal of the cyst in humans. Attempts have been made to compare the properties of certain enzymes present in the parasite with those of the corresponding host in the hope of discovering inhibitors that would inhibit the parasite enzyme(s) selectively. In the present report certain properties of phosphoglucose isomerase of the ovine liver cyst fluid have been compared with those of the healthy ovine liver. The enzymes from both sources purified by the same procedure exhibited the following properties: (1) identical pH optimum (8.5), (2) no detectable inhibition in the presence of phosphate ion up to 4.1 mM, (3) marked differences in the Km value, 8.7 mM and 10.7 mM for the parasite and host enzymes respectively, and (4) higher thermostability of the parasite enzyme as compared with the host enzyme.
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