Effect of ethionine on dolichyl phosphate-dependent transglycosylation reactions in rat liver

Dolichyl phosphates of different chain length (C35, C55 , C75 , Dol-mixture of C90 , 95, 100, 105 and C110 ) were tested as lipid acceptors in transglycosylation reactions. In the absence of exogenously added dolichyl phosphates there were no differences in the rate of synthesis in liver of dolichyl phosphate mannose, dolichyl phosphate glucose and dolichyl pyrophosphate N-acetylglucosamine between normal and ethionine-treated animals. Addition of exogenous dolichyl phosphates of different chain length stimulated the synthesis of dolichyl phosphate mannose and dolichyl pyrophosphate N-acetyl-glucosamine 2 to 4 times depending on the chain length of dolichols , both in normal and ethionine-treated animals. In liver of ethionine-treated rats the formation of dolichyl phosphate glucose was not stimulated. Following ethionine treatment the concentration of free and esterified with fatty acids dolichols was increased.     

The occurrence of long chain polyprenols in leaves of plants of Rosaceae family and their isolation by time-extended liquid chromatography.

The long chain polyprenols composed of 30 and more isoprene units from leaves of plants belonging to the genera Potentilla and Rosa have been described. They occur in the form of fatty acid esters. The composition of polyprenol mixture was species dependent and its content reached ca. 0.5% wet weight. Large scale preparation of individual polyprenols from a natural polyprenol mixture was performed using time-extended liquid chromatography on the hydrophobic gel Lipidex-5000.     

Effect of cimetidine on the heart conduction system]

An effect of cimetidine on ECG records has been investigated in a group of 40 patients with gastric or duodenal ulcers and coexisting circulatory disorders. For this purpose ECG has been recorded with Holter's technique (Medilog 2000) together with ECG-recording using high amplifying technique. An intravenous injection of 200 mg of cimetidine produced in some of patients inhibition of the sinus rhythm atrio-ventricular conduction disturbances as well as changes in the end phase of ECG ventricular image. The authors suggest, that intravenous administration of cimetidine to patients with cardiac diseases should be monitored with ECG recording.     

The influence of dolichol, dolichol esters, and dolichyl phosphate on phospholipid polymorphism and fluidity in model membranes

The effect of dolichols, polyprenols, dolichol esterified with fatty acids, and dolichyl phosphate on the structure and fluidity of model membranes was studied using 31P NMR, small-angle x-ray scattering, differential scanning calorimetry, and freeze-fracture electron microscopy. These studies suggest that dolichol and dolichol derivatives destabilize unsaturated phosphatidylethanolamine containing bilayer structures and promote hexagonal II phase formation; high concentrations of dolichol induce lipid structures characterized by "isotropic" 31P NMR and particulate fracture faces; dolichol, contrary to cholesterol, has no effect on the thermotropic behavior of membranes consisting of phosphatidylcholine, while dolichyl-P incorporation abolishes the transition from the gel to liquid crystalline phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine; both dolichol and dolichyl-P increase the fatty acid fluidity in phosphatidylethanolamine mixtures; the effect of dolichol on bilayer structure and fluidity is more pronounced with increasing number of isoprene residues; dolichol esters are only soluble to a limited extent in the bilayer and segregates into domains at low concentrations; the results are consistent with a localization of dolichyl-P in which the phosphate group is oriented to the water interphase. The induction of hexagonal II phase by dolichyl-P may elicit the transmembrane movement of glycosylated lipid intermediate.     

Biosynthesis of trans,trans,trans-geranylgeranyl diphosphate by the cytosolic fraction from rat tissues.

The cytosolic fractions from rat liver, brain, kidney, spleen and testis demonstrate the capacity to synthesize two products from [3H]isopentenyl diphosphate, i.e., farnesyl diphosphate and geranylgeranyl diphosphate. The highest rate of geranylgeranyl diphosphate synthesis was found in brain, testis and spleen, accounting for up to 30% of the total incorporation of radioactivity under optimal conditions. In all tissues examined the geranylgeranyl diphosphate formed was identified as the trans,trans,trans-isomer. The ratio of geranylgeranyl diphosphate to farnesyl diphosphate produced was specific for the tissue investigated and could be altered by the addition of divalent cations. The results in this study demonstrate the presence of a specific trans,trans,trans-geranylgeranyl diphosphate synthetase showing high affinity for farnesyl diphosphate.     

Voltage-dependent behaviour of dolichyl phosphate-phosphatidylcholine bilayer lipid membranes

The current-voltage steady-state characteristics, cyclic voltammograms and capacitance-voltage steady-state relationships of bilayer lipid membranes made from dioleoylphosphatidylcholine or its mixtures with dolichyl-12 phosphate have been studied. Sustained fluctuations of the capacitance of dolichyl phosphate modified bilayers under applied voltage were observed. The results suggest that the dynamics of dolichyl phosphate molecules in membranes can be regulated by transmembrane electrical potential.