Metabolic behavior of acetyl glyceryl ether phosphorylcholine on interaction with rabbit platelets

The metabolic fate of 1-O-[³H]alkyl-2-acetyl-sn-glycero-3-phosphorylcholine ([³H]-AGEPC) upon interaction with rabbit platelets was investigated. [³H]AGEPC was converted to a product identified as the long-chain fatty acyl analog. The reaction was unaffected by extracellular calcium. After a lag time of 30 to 60 s the kinetics of the conversion was linear. The rate of the reaction was found to be a function of platelet and AGEPC concentrations. Of the [³H]AGEPC (10^?9m) 85 ± 5% was processed into the-long chain fatty acyl analog within 1 h when incubated at 37 2C with a 1.25 × 10⁹ platelets per milliliter suspension. A maximal number of 1200 to 3600 [³H]AGEPC molecules were converted to the long-chain fatty acyl derivative per minute per platelet in the presence of 2 mm EDTA. Under similar conditions the 1-O-[³H]alkyl-2-(lyso)-sn-glycero-3-phosphorylcholine ([³H]lysoGEPC) also was transformed to a comparable long-chain fatty acyl derivative at a much slower rate and to a lower extent. No significant increase in lysoGEPC was noted in incubation mixtures containing [³H]AGEPC. The possible direct transacylation of AGEPC upon interaction with platelets is discussed as well as the possible involvement of this reaction in directly triggering the platelet response to AGEPC stimuli.     

Comparing multiple correspondence and principal component analyses with biomechanical signals. Example with turning the steering wheel

The purpose of this article is to compare Principal Component Analysis (PCA) and a much less used method, i.e. MCA (Multiple Correspondence Analysis) with data being first changed into membership values to fuzzy space windows. For such a comparison, data from an experimental study about turning the steering wheel is used. In a didactic perspective, this article only considers one multidimensional signal with 5 components: 3 linked to the steering wheel angle and hand positions and 2 to hand effort variables. A discussion weighs out the pros and the cons of both methods with criteria such as the possibility to show complex relational phenomena, the analysis/computing time or the information loss inherent to the averaging stage (in the perspective to analyze several hundreds of large multidimensional signals).     

Conversion of 5′-Methylthioadenosine into S-adenosylmethionine by yeast cells

5′-Methylthio[U-¹⁴C]adenosine was used as a culture supplement for Candida utilitis. The resulting S-adenosylmethionine was hydrolyzed into its structural components. Virtually none of the label of the pentose was found in the carbohydrate part of the intracellular S-adenosylmethionine. Much of it was present in the four-carbon chain of the methionine part of the sulfonium compound. The U-¹⁴C)-labeled adenine of 5′-methylthio[U-¹⁴C]adenosine did not contribute to the labeling of the amino acid component of the sulfonium compound.     

Adaptation to salinity at the plant cell level

Summary Various mechanisms of adaptation of plant cells to salinity are reviewed: (1) protection of enzymes and maintenance of turgor by organic solutes; (2) prevention of ion toxicity by compartmentation; and (3) energization of solute transport by the proton pump. All these mechanisms seem to play a role in adaptation. The particular advantages of using salt-adapted cells in suspension culture to identify mechanisms of adaptation are pointed out.     

Rapid group separations of nucleotides and related compounds on silica columns

Nucleosides, bases, and nucleotides can be separated from one another rapidly (10–15 min) on 1-ml silica cartridges. Samples adjusted to 4 mm ammonium borate, 90% acetonitrile are loaded onto 1-ml columns equilibrated with the same solvent. Bases do not absorb to the silica under these conditions. Nucleosides are eluted with 16 ml of 0.5 m acetic acid in 90% acetonitrile. Nucleotides are then eluted with water. The 1-ml silica columns have performed well with samples up to 10 ml in volume. We have found the procedure to be quantitative and the gels to have high capacity (61 μmol Cyd/ml silica). Acid extracts from a large number of cells (10⁸) have been processed on a single cartridge.     

The abnormal phosphorylation of spectrin in human hereditary spherocytosis

The phosphorylation of the proteins of the erythrocyte membrane of patients suffering from hereditary spherocytosis is investigated in intact erythrocytes by their incubation in the presence of radioactive inorganic phosphate. Examination of the phosphorylated components by high-resolution two-dimensional gel electrophoresis reveals only one defect in the pathological membranes, a depressed phosphorylation of the smaller polypeptide of spectrin; band 2. The phosphorylation of band 2 is measured with reference to the phosphorylation of syndein ($\text{2.1 + 2.2 + 2.3}$). In patients showing overt clinical symptoms and for whom splenectomy is advocated the phosphorylation of band 2 is depressed by approx. 70%. After splenectomy the phosphorylation of membrane proteins is restored to normal levels.     

In vitro growth of murine T cells. IV. Use of T-cell growth factor to clone lymphoid cells

Murine bone marrow cells can suppress the in vitro primary antibody response of normal spleen cells without apparent cytotoxicity. The bone marrow cells suppress the response to both T-dependent (SRBC) and T-independent (DNP-Ficoll) antigens. When bone marrow cells are fractionated on a sucrose density gradient, the suppressive activity is found in the residue rather than the lymphocyte fraction. The suppressive activity is either unaffected or enhanced by treatment with anti-T- and anti-B-cell serums. Pretreatment of mice with phenylhydrazine which reduces the number of pre-B cells did not reduce the suppressive activity of their bone marrow cells. Suppressive activity is abolished by irradiation of the marrow cells in vitro with 1000 R prior to assay. The activity is present in the marrow of thymus deficient (nude) mice, infant mice, and mice which have been made polycythemic by transfusion. Furthermore, the suppressor cell can phagocytize iron carbonyl particles, is slightly adherent to plastic and Sephadex G-10, and can bind to EA monolayers. We conclude that the suppressor cell is not a mature lymphocyte or granulocyte nor a member of the erythrocytic series, but is likely to be an immature cell possibly of the myeloid series. We speculate on the physiologic role of this cell.     

Subunit composition of a high molecular weight oligomer: Limulus polyphemus hemocyanin

The hemocyanin of Limulus polyphemus is a 48-subunit aggregate. This 3.3 × 10⁶-dalton oligomer is composed of structurally and functionally heterogeneous subunits. Using polyacrylamide electrophoresis J. Markl, A. Markl, W. Schartau, and B. Linzen (J. Comp. Physiol. Ser. B130,283–292, 1979) observed 12 bands; while using immunoelectrophoresis, M. Hoylaerts, G. Preaux, R. Witters, and R. Lontie (Arch. Int. Physiol. Biochem.87, 417–418, 1979) and J. Lamy, J. Lamy, J. Weill, J. Bonaventura, C. Bonaventura, and M. Brenowitz. (Arch. Biochem. Biophys.196, 324–339, 1979) observed 8 subunits. To proceed with an analysis of subunit roles in assembly it is first necessary to determine the number of distinct subunits. Refinement of the chromatographic separation procedures has led to the isolation of 8 immunologically distinct subunits as well as additional charge isomers which cannot be distinguished immunologically. Alkaline electrophoresis revealed 15 bands and isoelectric focusing up to 17. On the basis of extensive control experiments, including composit acrylamide-agarose immunoelectrophoresis and checks for conformational isomers, aggregation, proteolysis, and other types of degradation, we conclude that the electrophoretic heterogeneity of immunologically identical subunits is not artifactual. We have extended the nomenclature used by Lamy et al. (1979) to include the electrophoretic heterogeneity by using primes (′) to denote electrophoretically distinguishable subunits which are immunologically identical. A number of patterns have become apparent by correlating the results obtained by the different techniques. For example, immunologically pure subunit II, which shows 3 bands on alkaline electrophoresis, is in fact a mixture of electrophoretically distinct subunits II, II′, II″. Except for subunits II, II′, and II″ immunoelectrophoretically identical subunits are typically homogeneous on sodium dodecyl sulfate-gels. However, slight differences in the apparent molecular weight are observed on high-resolution gels between immunologically unrelated subunits. The immunological identity and electrophoretic differences suggest that the charge isomers which are immunologically identical have similar antigenic surfaces. If a charge substitution is not in a critical location, we would expect the electrophoretically distinct but immunologically identical subunits to have identical assembly roles. Comparison of the results for Limulus hemocyanin with the hemocyanin of related species Eurypelma californicum and Androctanus australis, which have 7 and 8 immunologically distinct subunits, respectively, suggests that the calcium-mediated aggregation from 24 to 48 subunits of Limulus does not require more extensive subunit complexity.     

Asymmetry of the phospholipid bilayer of rat liver endoplasmic reticulum

The phospholipids of intact microsomal membranes were hydrolysed 50% by phospholipase C of Clostridium welchii, without loss of the secretory protein contents of the vesicle, which are therefore not permeable to the phospholipase. Phospholipids extracted from microsomes and dispersed by sonication were hydrolysed rapidly by phospholipase C-Cl. welchii with the exception of phosphatidylinositol. Assuming that only the phospholipids of the outside of the bilayer of the microsomal membrane are hydrolysed in intact vesicles, the composition of this leaflet was calculated as 84% phosphatidylcholine, 8% phosphatidylethanolamine, 9% sphingomyelin and 4% phosphatidylserine, and that of the inner leaflet 28% phosphatidylcholine, 37% phosphatidylethanolamine, 6% phosphatidylserine and 5% sphingomyelin. Microsomal vesicles were opened and their contents released in part by incubation with deoxycholate (0.098%) lysophosphatidylcholine (0.005%) or treatment with the French pressure cell. Under these conditions, hydrolysis of the phospholipids by phospholipase C-Cl. welchii was increased and this was mainly due to increased hydrolysis of those phospholipids assigned to the inner leaflet of the bilayer, phosphatidylethanolamine and phosphatidylserine. Phospholipase A₂ of bee venom and phospholipase C of Bacillus cereus caused rapid loss of vesicle contents and complete hydrolysis of the membrane phospholipids, with the exception of sphingomyelin which is not hydrolysed by the former enzyme.