| 1. |
|
|
| 2. |
- Jacobsson, B, et al.
(author)
-
Abnormality of adenylate cyclase regulation in human platelet membranes in renal insufficiency.
- 1985
-
In: European journal of clinical investigation. - 0014-2972. ; 15:2, s. 75-81
-
Journal article (peer-reviewed)abstract
- Adenylate cyclase in human platelets is under dual control of prostaglandins (PGI2 and PGE1) and catecholamines. The adenylate cyclase complex in membranes of platelets from ten patients with uraemia was investigated. The activation of the platelet cyclase by PGE1 is increased in the uraemic state, Vmax 4436 +/- 607 pmol cAMP mg-1 15 min-1. In the normal state Vmax is 2098 +/- 309 pmol cAMP mg-1 15 min-1. The alpha 2-adrenergic receptor was assayed with 3H-yohimbine binding. The density of receptors was equal in the uraemic (175 fmol mg-1 membrane protein) and the normal (170 fmol mg-1 membrane protein) states. Norepinephrine/3H-yohimbine competition binding revealed that catecholamines were bound with normal affinity in platelets in uraemia. Yet the inhibition of adenylate cyclase through the alpha 2-adrenergic receptor was diminished since Vmax values of adenylate cyclase with PGE1 and PGE2 + norepinephrine did not significantly differ. In the normal state, norepinephrine significantly (P less than 0.05) inhibited the PGE1 stimulated cyclase. It is concluded that platelet adenylate cyclase in the uraemia has an increased capacity for activation which is the result of both a sensitized stimulatory mechanism (prostaglandin mediated) and a deficient inhibitory mechanism (catecholamine mediated). It is suggested that a defect exists in the inhibitory nucleotide binding protein (NI) which is the coupling unit between the adenylate cyclase catalytic subunit (C).
|
|
| 3. |
- Lidholt, Kerstin, et al.
(author)
-
Biosynthesis of heparin : Modulation of polysaccharide chain length in a cell-free system
- 1988
-
In: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 254:2, s. 571-578
-
Journal article (peer-reviewed)abstract
- The formation of heparin-precursor polysaccharide (N-acetylheparosan) was studied with a mouse mastocytoma microsomal fraction. Incubation of this fraction with UDP-[3H]GlcA and UDP-GlcNAc yielded labelled macromolecules that could be depolymerized, apparently to single polysaccharide chains, by alkali treatment, and thus were assumed to be proteoglycans. Label from UDP-[3H]GlcA (approx. 3 microM) is transiently incorporated into microsomal polysaccharide even in the absence of added UDP-GlcNAc, probably owing to the presence of endogenous sugar nucleotide. When the concentration of exogenous UDP-GlcNAc was increased to 25 microM the rate of incorporation of 3H increased and proteoglycans carrying polysaccharide chains with an Mr of approx. 110,000 were produced. Increasing the UDP-GlcNAc concentration to 5 mM led to an approx. 4-fold decrease in the rate of 3H incorporation and a decrease in the Mr of the resulting polysaccharide chains to approx. 6000 (predominant component). When both UDP-GlcA and UDP-GlcNAc were present at high concentrations (5 mM) the rate of polymerization and the polysaccharide chain size were again increased. The results suggest that the inhibition of polymerization observed at grossly different concentrations of the two sugar nucleotides, UDP-GlcA and UDP-GlcNAc, may be due either to interference with the transport of one of these precursors across the Golgi membrane or to competitive inhibition of one of the glycosyltransferases. The maximal rate of chain elongation obtained, under the conditions employed, was about 40 disaccharide units/min. The final length of the polysaccharide chains was directly related to the rate of the polymerization reaction.
|
|
| 4. |
- Penayo, U, et al.
(author)
-
Community attitudes and awareness of mental disorders : a key informant study in two Nicaraguan towns
- 1988
-
In: Acta Psychiatrica Scandinavica. - 0001-690X .- 1600-0447. ; 78:5, s. 561-566
-
Journal article (peer-reviewed)abstract
- Attitudes towards mentally ill people were studied in two Nicaraguan towns through interviews with key informants. They were presented 8 case histories originally developed in a World Health Organization collaborative study. Alcoholism and depressive neurosis were considered the most common disorders, while the schizophrenic case was generally judged as the most severe. The methodology was found useful and valid.
|
|
