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Biomedical subjects

W A Scott

Publications and source records attributed to W A Scott.

At least 145 records · Page 8Linked to original sources
PubMed1978

Purification and characterization of calcium-binding protein from chick chorioallantoic membrane.

A procedure is described for the purification of the calcium-binding protein (CaBP) from the chorioallantoic membrane of the chick embryo. With this scheme, a 180- to 200-fold purification was achieved with a 40% yield. Characterization of the CaBP revealed that its properties differ from those of previously studied calcium-binding proteins. The CaBP has a molecular weight of 95,000 to 100,000 and appears to be composed of four subunits of identical molecular weight (22,000 to 25,000). The CaBP is a basic protein as indicated by its high electrophoretic mobility under acidic conditions and its relatively high isoelectric point of 8.06. The calcium-binding activity of the CaBP is sulfhydryl dependent and highly specific for calcium ions (10 high affinity sites, ka = 2.35 X 10(7) m-1; 100 to 120 low affinity sites, ka = 2.00 X 10(5) M-1). Amino acid analysis indicated that the CaBP contains 2 to 10 residues of a modified amino acid, gamma-carboxyglutamate (gamma-CGlu). The presence of gamma-CGlu residues suggested that vitamin K may be involved in the expression of the CaBP in the chorioallantoic membrane.

Allantois↗
PubMed1978

Calcium-binding protein of the chick chorioallantoic membrane. I. Immunohistochemical localization.

The preparation of a specific antiserum (anti-CaBP) against the calcium-binding protein (CaBP) of the chorioallantoic membrane (CAM) is described. The anti-CaBP appeared to be specific for the CaBP by immunodiffusion and immunoelectrophoresis. Application of the anti-CaBP in immunofluorescence histochemistry revealed that the CaBP is present in the CAM only at developmental ages corresponding with the expression of the calcium transport function of the membrane. Furthermore, the CaBP is localized to the ectoderm of the CAM, appears to be exposed to the entire external surface of the ectoderm, and can be shown to be associated with cells enzymatically dissociated from the CAM. These results are consistent with a functional role of the CaBP in the CAM calcium transport process.

Animals↗
PubMed1978

Calcium-binding protein of the chick chorioallantoic membrane. II. Vitamin K-dependent expression.

A simple method was devised for the maintenance of the chorioallantoic membrane (CAM) of chick embryos in organ culture. Explants of CAM survived for up to 5 days in this system and retained the characteristic three-layered morphology (ectoderm, mesoderm, and endoderm). Induction of the CAM calcium-binding protein (CaBP) by effectors of calcium metabolism was studied in these organ cultures. Vitamin K was found to elicit a seven- to eightfold increase in CaBP, whereas no increase in CaBP activity occurred on supplementation with vitamin A, parathyroid hormone, an analogue of vitamin D, vitamin D and its hydroxylated metabolites, or with elevated calcium levels. The vitamin K-mediated induction of CaBP was dose-dependent, inhibited by the vitamin K antagonists warfarin and dicoumarol, selective for vitamin K5, and maximal at the developmental stage (13-15 days of incubation) corresponding to the onset of calcium transport by the CAM in vivo. CaBP levels increased after 60-70 h in cultures of 13-15 day CAM supplemented with vitamin K and reached maximal levels around 80-90 h of culture. The CAM ectoderm underwent extensive proliferation and often assumed a villuslike morphology in the vitamin K cultures.

Age Factors↗
PubMed1977

Response of endocytosis to altered fatty acyl composition of macrophage phospholipids.

Mouse peritoneal macrophages incubated in serumless medium containing a 19:0 or trans-18:1 fatty acid complexed to bovine serum albumin incorporate the exogenous fatty acid supplement into cellular phospholipids. Within 8 hr, 25% of the total phospholipid fatty acids are derived from the supplement, with cell viability remaining greater than 95%. The incorporation of either of these supplements increases the saturated/unsaturated fatty acid ratio in the phospholipids 2-fold over that of cells cultured in serum and effects striking changes in endocytic activities. The levels of both fluid-phase pinocytosis and receptor-mediated phagocytosis are decreased at all temperatures examined between 15 degrees and 37 degrees. The increased degree of saturation of cell phospholipids correlates with decreased endocytic rates for both processes and with increased activation energies (Eact) for phagocytosis. The Eact values for phagocytosis, which range from 54 to 90 kcal/mol, depend on the supplementation conditions used. Although the levels of pinocytosis are depressed, the Eact values for pinocytosis (17--25 kcal/mol) are not strikingly affected by saturated fatty acid enrichment. These observations suggest that the degree of lipid fluidity of macrophage membranes influences both phagocytosis and pinocytosis in macrophages.

Acetates↗
PubMed1977

Calcium-binding protein of chorioallantoic membrane: identification and development expression.

A calcium-binding protein (CaBP) which has a molecular weight of 100,000 and an isoelectric point of 8.0 has been isolated from the chorioallantoic membrane (CAM) of the chick embryo. Expression of the CaBP occurs simultaneously with the onset of calcium absorption from the egg shell by the CAM, and the temporal increase in CaBP activity is coincident with calcium deposition in the embryo. The CAM CaBP differs in properties from the CaBPs of the adult organs, including the vitamin-D-dependent protein of intestine.

Adenosine Triphosphatases↗
PubMed1977

Unsaturated fatty acid mutants of Neurospora crassa.

Unsaturated fatty acid (ufa) auxotrophs of Neurospora crassa were obtained by treatment of conidia with N-methyl-N'-nitro-N-nitrosoguanidine followed by isolation on media containing polyunsaturated fatty acids suspended in Tergitol NP-40. The 24 mutants for which reisolates were obtained from crosses with wild type were assigned to two complementation classes, ufa-1 and ufa-2, located on linkage group V. Unsaturated fatty acids with varying degrees of unsaturation, chain length, and double-bond position as well as different steric configurations were tested for growth requirements.

Crosses, Genetic↗
PubMed1976

Adenosine 3':5'-cyclic monophosphate deficiency in Neurospora crassa.

Depending on growth conditions, the adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels of the fr mutant, a morphologically aberrant strain of Neurospora crassa, are reduced 2- to 5-fold. By taking advantage of the differences in phenotype of fr in liquid and agar cultures and the positive response of fr grown on solid support to exogenous theophylline, a relationship between the degree of morphological abnormality and intracellular cyclic AMP levels of the mutant is observed. Progressive restoration of the fr phenotype toward a normal state is paralleled by increases in cyclic nucleotide content. Striking differences in the sedimentation and thermal characteristics of the fr and wild-type adenylate cyclases [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] are observed. Approximately 50% of the normal activity sediments at 105,000 X g compared to 5% of the mutant enzyme. In addition, the overall stability of the fr adenylate cyclase is significantly decreased and its rate of inactivation at 37 degrees in the absence of substrate is 10-fold greater than the wild-type adenylate cyclase. Arrhenius plots also indicated that the Q10 (increase in rate per 10 degrees temperature increase) and the temperature of maximal activity of the fr enzyme are reduced. Supplementation of fr agar cultures with linolenic acid results in an elevated cyclic AMP content and a wild-type-like morphology similar to that obtained with inhibitors of phosphodiesterase (3':5'-cyclic AMP 5'-nucleotidohydrolase, EC 3.1.4.17). An increased thermostability of the fr adenylate cyclase occurs on linolenate enrichment of the mutant. It is concluded that the cyclic AMP deficiency is at least partially responsible for the fr phenotype and that this reduction results from a membrane defect that affects adenylate cyclase function.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1975

Adenosine 3',5'-cyclic monophosphate and morphology in Neurospora crassa: drug-induced alterations.

Grown in liquid culture in the presence of a variety of structurally unrelated drugs, mycelia of wild-type Neurospora assume a colonial or semicolonial growth habit similar to that of known morphological mutants. Drugs that produce these morphological changes include atropine, theophylline, histamine, and several of the quinoline-containing antimalarials. Each of these drugs decrease the endogenous adenosine 3',5'-cyclic monophosphate (cAMP) concentration of mycelia as a result of their effect on the activity of adenyl cyclase, the cAMP-dependent phosphodiesterase, or both. The evidence indicates a relationship between the degree of morphological abnormality, the degree to which intracellular cAMP is reduced, and the action of the drugs on the adenyl cyclase and phosphodiesterase.

Adenylyl Cyclases↗