Procedural paternalism in competency determination.
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When CCK33 was iodinated at His 20 with lactoperoxidase, the labelled hormone was less immunoreactive under radioimmunoassay conditions than CCK39 which is readily iodinated at Tyr 1. Since the difference in immunoreactivities could not be due to different degrees of oxidative damage, the regional specificity of the assay antibody (UT122, from the laboratory of J.C. Thompson, University of Texas) was re-examined. A synthetic parital sequence, CCK33 6-16, which had similar conformation to the same sequence in the intact peptide, as shown by CD analysis, was devoid of immunoreactivity. Results with sulphated and non-sulphated C-terminal octapeptides of the hormone, CCK8 (CCK33 27-33), indicate limited dependence of the C-terminal region for binding to antibody. Thus, the lower binding with 125I-CCK33 than with 125I-CCK39 indicates that His 20 is an important feature of the immunogenic site and that the iodine atom is large enough to cause steric hindrance. This explains why the method of iodination might have to be varied depending on the regional specificity of antibodies.
A review of squamous neoplasia of the endometrium (in situ and/or invasive) with or without coexistent similar disease of the cervix, revealed four anatomical variants in 22 patients. The patterns were: Group (i), endometrial squamous neoplasia only; Group (ii), discontiguous endometrial and cervical squamous neoplasia; Group (iii), possibly discontiguous endometrial and squamous neoplasia; and Group (iv), contiguous endometrial and squamous disease. The details of the histology, management and outcome are discussed, the latter being much poorer for the fourth group. The criteria for diagnosing squamous neoplasia involving the endometrium are re-examined and a recommendation for these criteria is suggested.
The effect of ethanol (E) on the radial growth rate (mu) of food spoilage moulds (Aspergillus candidus, Aspergillus flavus, Aspergillus niger, Cladosporium cladosporioides, Eurotium herbariorum, Mucor circinelloides, Mucor racemosus, Paecilomyces variotii, Penicillium chrysogenum, Penicillium digitatum, Rhizopus oryzae and Trichoderma harzianum) was assessed in Potato Dextrose Agar (PDA) medium at a(w) 0.99, 25 degrees C. In order to model this effect, the Monod type equation described previously by Houtsma et al. (Houtsma, P.C., Kusters, B.J.M., de Wit, J.C., Rombouts, F.M., Zwietering, M.H., 1994. Modelling growth rates of Listeria monocytogenes as a function of lactate concentration. Int. J. Food. Microbiol. 24, 113-123.) was re-parameterised: mu = mu(opt)[K(E(max)-E)/K E(max)-2KE+E(max)E]; E(max) (%, wt/wt): ethanol concentration at which no growth occurs, K (%, wt/wt): ethanol concentration at which mu = mu(opt)/2, mu(opt) (mm day(-1)): growth rate at 0% ethanol. The model was capable of describing curves, mu vs. E, with either a concave shape (K E(max)/2) with a good accuracy (root mean square error (RMSE) < or = 0.136) with the notable exception of R. oryzae and T. harzianum. After growth rate data were square-root transformed to stabilise the variance, E(max) was estimated in the range 3% to 5% for all moulds with the exception of T. harzianum (E(max) 2.14%) and P. variotii (E(max) 6.43%). Ethanol would appear an effective additional barrier to inhibit fungal growth in food products and would represent an interesting alternative to the use of preservatives.
A single unattached kinetochore can delay anaphase onset in mitotic tissue culture cells (Rieder, C.L., A. Schultz, R. Cole, G. Sluder. 1994. J. Cell Biol. 127:1301-1310). Kinetochores in vertebrate cells contain multiple binding sites, and tension is generated at kinetochores after attachment to the plus ends of spindle microtubules. Checkpoint component Mad2 localizes selectively to unattached kinetochores (Chen, R.-H., J.C. Waters, E.D. Salmon, and A.W. Murray. 1996. Science. 274:242-246; Li, Y., and R. Benezra. Science. 274: 246-248) and disappears from kinetochores by late metaphase, when chromosomes are properly attached to the spindle. Here we show that Mad2 is lost from PtK1 cell kinetochores as they accumulate microtubules and re-binds previously attached kinetochores after microtubules are depolymerized with nocodazole. We also show that when kinetochore microtubules in metaphase cells are stabilized with taxol, tension at kinetochores is lost. The phosphoepitope 3f3/2, which has been shown to become dephosphorylated in response to tension at the kinetochore (Nicklas, R.B., S.C. Ward, and G.J. Gorbsky. 1995. J. Cell Biol. 130:929-939), is phosphorylated on all 22 kinetochores after tension is reduced with taxol. In contrast, Mad2 only localized to an average of 2.6 out of the 22 kinetochores in taxol-treated PtK1 cells. Therefore, loss of tension at kinetochores occupied by microtubules is insufficient to induce Mad2 to accumulate on kinetochores, whereas unattached kinetochores consistently bind Mad2. We also found that microinjecting antibodies against Mad2 caused cells arrested with taxol to exit mitosis after approximately 12 min, while uninjected cells remained in mitosis for at least 6 h, demonstrating that Mad2 is necessary for maintenance of the taxol-induced mitotic arrest. We conclude that kinetochore microtubule attachment stops the Mad2 interactions at kinetochores which are important for inhibiting anaphase onset.
Previous spectroscopic studies on the phycocyanobilin-containing peptide beta-2T from Synechococcus sp. 6301 C-phycocyanin and the phycoerythrobilin-containing peptide beta-2TP from Porphyridium cruentum B-phycoerythrin indicated a different single thioether mode of attachment, postulated to be through the D-ring of the tetrapyrrole, in contrast to the A-ring linkage established for the other singly linked bilins in these proteins (Bishop, J.E., Lagarias, J.C., Nagy, J. O., Schoenleber, R.W., Rapoport, H., Klotz, A.V., and Glazer, A.N. (1986) J. Biol. Chem. 261, 6790-6796; Klotz, A.V., Glazer, A.N., Bishop, J.E., Nagy, J.O., and Rapoport, H. (1986) J. Biol. Chem. 261, 6797-6805). The crystal structure of Agmenellum quadruplicatum C-phycocyanin at 2.5-A resolution (Schirmer, T., Bode, W., and Huber, R. (1987) J. Mol. Biol., 196, 677-695) supports an A-ring linkage for all three phycocyanobilins. Consequently we have re-evaluated our proposed structural assignments by further 1H NMR studies. Two-dimensional homonuclear correlated and nuclear Overhauser enhancement spectroscopic data presented here show that all three bilins in Synechococcus 6301 C-phycocyanin are attached solely through the A-ring, complementary to the crystallographic data. The evidence from the NMR data for all bilin peptides examined includes the dipoledipole interactions of the 5-H with the 3-H, 3'-H, and a pyrrole methyl group (7-CH3); the corresponding interactions would not be possible in a D-ring-linked bilin. The 5-H also consistently exhibits allylic J-coupling to the 3-H, supporting A-ring linkage assignment. These data are inconsistent with the alternative D-ring linkage assignment since this would involve J-coupling through five bonds. Examination of the phycoerythrobilin beta-2 position in B-phycoerythrin also reveals an A-ring type of attachment by similar criteria. We conclude that all singly linked bilins are attached through the A-ring.