Febs Letters

doi: 10.1016/0014-5793(85)81101-7pmid: N/A

Wistow, Graeme

doi: 10.1016/0014-5793(85)81102-9pmid: 3972098

Mieskes, Gottfried; Söling, Hans-Dieter

doi: 10.1016/0014-5793(85)81103-0pmid: 2982655

A recently described 6‐phosphofructo‐1‐kinase phosphatase (PFK‐phospatase [1]) shared several properties with protein phosphatase 2C [2,3], but exhibited differences with respect to molecular mass and substrate specificity. Chromatography on histone‐Sepharose, gel filtration experiments on Sephacryl S‐200 and Sephadex G‐100 as well as sucrose density gradient centrifugation [4] show that both enzyme preparations behave identically under all experimental conditions used. The low activity of PFK‐phosphatase phosphorylated histone H2B [1] had resulted from an inhibition of the enzyme by high concentrations of this substrate. The apparent molecular mass of protein phosphatase 2C as calculated from Sephacryl chromatography and sedimentation analysis is about 90 kDa, the molecular mass obtained by SDS gel electrophoresis about 45 kDa. The native enzyme therefore seems to be a dimer consisting probably of 2 identical subunits. Accordingly, the previously described PFK‐phosphatase is protein phosphatase 2C.

Enrich, Carlos; Gahmberg, Carl G.

doi: 10.1016/0014-5793(85)81104-2pmid: 3156048

Cell‐surface glycoproteins of rat liver sinusoidal plasma membranes from control and regenerating livers were studied. The glycoproteins were labeled using specific methods for sialic acid (NAIO4/NaB3H4) and galactosyl/N‐acetyl galctosaminyl residues (galactose oxidase/NaB3H4 and neuraminidase‐galactose oxidase (NaB3H4) and the solubilized proteins were analyzed by gel electrophoresis. The patterns obtained with regenerating livers were quantitatively different from controls. This shows that cell surface glycoproteins change during liver regeneration.

Tremblay, Johanne; Gerzer, Rupert; Vinay, Patrick; Pang, Stephen C.; Béliveau, Richard; Hamet, Pavel

doi: 10.1016/0014-5793(85)81105-4pmid: 2857657

We have demonstrated previously that atrial natriuretic factor (ANF) augments urinary, plasma and kidney cGMP levels but has no significant effect upon cAMP. Using cGMP as a marker, we searched for specific target sites involved in the action of ANF in the dog kidney, and observed no changeof cGMP in the proximal tubules, a 2‐fold increase over basal levels in the thick loop of Henle and a 3‐fold elevation in the collecting duct. The most striking action on cGMP occurred in the glomeruli with a rise of up to 50‐fold being evident at 1–2 min. after the addition of ANF. The results obtained in the absence or presence of a phosphodiesterase inhibitor support the notion that the effects of ANF were exerted at the level of guanylate cyclase stimulation rather than cGMP phosphodiesterase inhibition. The action of sodium nitroprusside (SNP), a direct stimulator of soluble guanylate cyclase, differed from that of ANF. The ability of the factor to enhance cGMP levels was correlated with the distribution of particulate guanylate cyclase. This study identifies the glomeruli and the distal part of the nephron as specific targets of ANF and implicates particulate guanylate cyclase as the enzyme targetted for the expression of its action.

Eisenthal, Robert; Panes, Alison

doi: 10.1016/0014-5793(85)81106-6pmid: 3972106

The ratio of glycerol to pyruvate produced by T. brucei incubated with glucose at various oxygen tensions has been used as an index of the aerobic and anaerobic pathways of glucose metabolism. A minimal model is presented which fits the observed data. The value of the notional K of the aerobic/anaerobic transition from the model is close to that of the K m of trypanosomal glycerophosphate oxidase. The anaerobic pathway appears to be almost completely inoperative at oxygen tensions in the range of those found in venous and arterial blood.

Conti, P.; Gigante, G.E.; Alesse, E.; Cifone, M.G.; Fieschi, C.; Reale, M.; Angeletti, P.U.

doi: 10.1016/0014-5793(85)81107-8pmid: 3972107

The DNA synthesis of lymphocytes triggered by phytohemagglutinin or phorbol‐myristate‐acetate is strongly reduced by the externally applied electromagnetic field (ELF). Ca2+ uptake by stimulated lymphocytes is also reduced by ELF. The effect appears to be synergistic with that of the well‐known calcium blocker agent, verapamil.

Khalfoun, B.; Degenne, D.; Arbeille-Brassart, B.; Gutman, N.; Bardos, P.

doi: 10.1016/0014-5793(85)81108-Xpmid: 3972108

Human full‐term syncytiotrophoblast plasma membranes isolated by mechanical procedures (sieving and ultrasonic disintegration), purified by phase centrifugation, form a single band of 1.052 ± 0.002 density in percoll gradient. The purity of the preparation was assessed by electron microscopy, enzyme analysis and β2‐microglobulin determination.

Miralles, Vicente J.; Grisolía, Santiago

doi: 10.1016/0014-5793(85)81109-1pmid: 3972109

Incubation of [35S]methionine labeled mitochondria from rat liver with rabbit reticulocyte lysate under the same conditions as those used in the import of mitochondrial protein precursors results in the release of mitochondrial proteins to the medium. Fractionation of the lysates with ammonium sulphate yields a fraction, essentially free of haemoglobin, which exhibits higher activity for the release of mitochondrial proteins than the starting lysate. The fraction has a molecular mass of > 10 kDa and is heat‐sensitive. The release is insensitive to inhibitors of reticulocyte lipoxygenase.

Leverve, X.M.; Groen, A.K.; Verhoeven, A.J.; Tager, J.M.

doi: 10.1016/0014-5793(85)81110-8pmid: 2857658

Isolated hepatocytes from fasted rats were perifused with glycerol as gluconeogenic substrate. Stimulation of gluconeogenesis with phenylephrine (10−5M) as α‐adrenergic agonist consisted of two distinct phases. The first phase was a transient stimulation of gluconeogenesis and was accompanied by transient changes in cytosolic and mitochondrial redox state; this phase was abolished by the transaminase inhibitor aminooxyacetate. The second phase was a stable stimulation of less magnitude, without change in redox state and insensitive to addition of aminooxyacetate. It is concluded that the first phase is due to a transient enhancement of flux through the malate/aspartate shuttle and that the stable phase is probably due to a stimulation of mitochondrial glycerol‐3‐phosphate dehydrogenase and glycerol kinase.