Febs Letters

doi: 10.1016/0014-5793(84)80819-4pmid: N/A

Budohoski, Leszek; John Challis, R.A.; McManus, Bronwyn; Newsholme, Eric A.

doi: 10.1016/0014-5793(84)80820-0pmid: 6199230

The concentration of insulin that produces half‐maximal stimulation of glycolysis by stripped soleus muscle preparations is markedly increased by the adenosine analogues, 2‐chloroadenosine and N 6‐phenylisopropyladenosine, but is markedly decreased by the methyl xanthine analogue, 8‐phenyltheophylline. 2‐Chloroadenosine increases the concentration of insulin required to stimulate glycolysis half maximally, from about 100 to 2000 μunits/ml. 8‐Phenyltheophylline decreases this concentration of insulin from about 100 to 10 μunits/ml, an effect which is similar to that produced either by addition of adenosine deaminase to the medium or to exercise‐training of the donor animals for 4 weeks.

Joost, H.G.; Göke, R.

doi: 10.1016/0014-5793(84)80821-2pmid: 6365589

The effects of islet‐activating protein (IAP), a Bordetella pertussis toxin, on insulin‐ and isoprenaline‐stimulated glucose transport were studied in isolated rat adipocytes. Basal as well as insulin‐stimulated glucose transport were not affected when cells were pretreated with IAP. In contrast, IAP pretreatment abolished the stimulatory effect of isoprenaline. When IAP‐pretreated cells were exposed to a combination of insulin and isoprenaline, the catecholamine significantly reduced the stimulatory effect of insulin. Since IAP is supposed to specifically block the inhibitory component Ni of adenylate cyclase, the results suggest that: (a) the effect of insulin is unrelated to the regulation of adenylate cyclase; (b) isoprenaline may exert both stimulatory and inhibitory effects depending on activation of Ni. The inhibitory regulation of adenylate cyclase may thus be a pivotal link in the regulation of glucose transport.

Young, P.; Arch, J.R.S.; Ashwell, Margaret

doi: 10.1016/0014-5793(84)80822-4pmid: 6698197

Cold acclimation has been shown to produce a substantial increase in the number of brown adipocytes in the parametrial fat pad of female BALB/c mice ‐ a site normally thought to consist of typical white adipocytes. The brown adipocytes have been identified not only on the basis of their morphology using light and electron microscopy, but also on the basis of the content of the mitochondrial ‘uncoupling protein’ (M r = 32 000) which is characteristic of the proton conductance pathway of brown adipose tissue.

Jónsdóttir, Ingileif; Ekre, Hans-Peter T.; Skoog, Bo; Perlmann, Peter

doi: 10.1016/0014-5793(84)80823-6pmid: 6698201

Monoclonal antibodies were used to study the immunochemical nature of charge isomers of bacterially produced methionyl human growth hormone. After isoelectric focusing of the hormone the 12 monoclonal antibodies reacted similarly in immunoblotting experiments and none of them could discriminate between the two isolated charge isomers in ELISA. This indicates that the generation of charge isomers of met‐hGH does not result is loss of the determinants recognized by the monoclonal antibodies and that the conformation of the two main charge isomers is identical within these determinants.

Berthon, Brigitte; Binet, Adrien; Mauger, Jean-Pierre; Claret, Michel

doi: 10.1016/0014-5793(84)80824-8pmid: 6698202

Cytosolic [Ca2+] has been measured by using the Ca2+‐sensitive indicator quin2 in rat liver cells. Optimal loading and hydrolysis have been obtained by equilibrating the cells with 50 μM quin2 acetoxymethyl ester for 150 s. The increase in [Ca2+]i initiated by noradrenaline and vasopressin was reduced but not abolished by removing external Ca2+.

Aitchison, Robert; West, David W.; Clegg, Roger A.

doi: 10.1016/0014-5793(84)80825-Xpmid: 6321236

High affinity cyclic AMP phosphodiesterase activity in preparation of acini isolated from mammary tissue of lactating rats is shown to be stimulated by the addition of physiological concentrations of insulin to incubations of acini in vitro. This effect is expressed specifically on membrane‐associated phosphodiesterase and occurs in the absence of concurrent protein synthesis. The possible functional role of this aspect of insulin's action on mammary tissue is discussed and compared with the well‐known reversal by this hormone of the effects of lipolytic agents in adipose tissue and liver.

Neumann, Stefan; Simon, Helmut

doi: 10.1016/0014-5793(84)80826-1pmid: N/A

Proteus mirabilis and Proteus vulgaris contain in the crude extract a non‐pyridine nucleotide dependent reductase for 2‐oxo‐acids as well as 2‐oxo‐dicarboxylic acids of specific activities of 1–10 units/mg protein. The enzyme catalyzes the reduction of very different 2‐oxo‐acids to the corresponding (2R)‐hydroxy‐acid. Reduced methyl‐ or benzylviologen act as artifical electron donors. The membrane‐bound enzyme has been enriched 167‐fold to a purity 90% as judged by electrophoresis. It seems that the enzyme does not contain flavin.

Lüdi, Hans; Hasselbach, Wilhelm

doi: 10.1016/0014-5793(84)80827-3pmid: 6141953

The four tryptic fragments of the Ca2+‐ and Mg2+‐dependent ATPase from sarcoplasmic reticulum were separated on a TSK‐G 4000 SW preparative high performance liquid chromatography column in the presence of sodium dodecyl sulfate. Using atomic absorption spectroscopy, the analysis of the protein peaks demonstrated that the calcium binding sites with high affinities are located in the smallest fragment (A2; 25 kDa).

Gutteridge, John M.C.; Quinlan, Gregory J.; Wilkins, Stephanie

doi: 10.1016/0014-5793(84)80828-5pmid: 6321237

Mitomycin C stimulates deoxyribose degradation with the release of thiobarbituric acid‐reactive material under conditions of low oxygen concentration. This damage is inhibited by scavengers of the hydroxyl radical, iron chelators and the specific proteins catalase and superoxide dismutase. The reactive radical species appears to arise from a Fenton‐type sequence in which iron is reduced by the mitomycin C semiquinone radical.