Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Lateral regionalization and diffusion of a maturation-dependent antigen in the ram sperm plasma membrane

We have used a monoclonal antibody ESA 152 in fluorescence recovery after photobleaching (FPR) studies of a maturation-dependent surface antigen of ram sperm. The antibody is an immunoglobulin G secreted by a hybridoma derived from NS1 mouse myeloma cells. The ESA 152 antigen is not detectable in testicular sperm. It is localized on the surface of ejaculated sperm where it is present on all regions of the surface, but tends to be concentrated on the posterior region of the head. The ESA 152 antigen can be extracted by detergents or chloroform-methanol. The extracted antigen is sensitive to proteases and migrates with an apparent Mr approximately 30,000 in SDS-containing 10-20% polyacrylamide gradient gels. FPR measurements of ESA 152 lateral mobility in the membrane yield diffusion coefficients in the range 10(-9)-10(-8) cm2/s, values typical of lipids but observed for proteins only at the fluid dynamic limit where diffusion is controlled by lipid fluidity. Immobile fractions, typical of membrane proteins, are observed on all regions. When the antigen is stained by a fluoresceinated Fab fragment of the ESA 152 antibody, the diffusibility is highly regionalized, with particularly low, but rapid, recovery on the midpiece. Cross-linking of the antigen with the intact ESA 152 antibody induces a redistribution in which the antigen is excluded from the posterior head region. This cross-linking is accompanied by increases in ESA 152 diffusibility on both the anterior head and the midpiece.     

Relationships of vervet mothers with sons and daughters from one through three years of age

Social relationships between mothers and juvenile offspring were examined in captive, socially-living vervet monkeys (Cercopithecus aethiops sabaeus) to assess the effects of offspring age and sex, and the mother's dominance rank on behavioural interactions. The results indicate that both high-and low-ranking mothers approach and groom their daughters more than they approach and groom their sons. The frequency of both aggressive behaviour toward offspring and support of offspring in agonistic encounters with other group members is influenced by the mother's dominance rank, but not by offsprin sex. Compared to sons, daughters (particularly daughters of high-ranking females) approach and groom their mothers more often, and support their mothers more often in intra-group aggression. The results are discussed in terms of several predictions from parental investment theory and the concept of mutualism.     

Ouabain-insensitive salt and water movements in duck red cells. II. Norepinephrine stimulation of sodium plus potassium cotransport

Catecholamines induce net salt and water movements in duck red cells incubated in isotonic solutions. The rate of this response is approximately three times greater than a comparable effect observed in 400 mosmol hypertonic solutions in the absence of hormone (W.F. Schmidt and T. J. McManus. 1977 a.J. Gen. Physiol. 70:59-79. Otherwise, these two systems share a great many similarities. In both cases, net water and salt movements have a marked dependence on external cation concentrations, are sensitive to furosemide and insensitive to ouabain, and allow the substitution of rubidium for external potassium. In the presence of ouabain, but the absence of external potassium (or rubidium), a furosemide-sensitive net extrusion of sodium against a large electrochemical gradient can be demonstrated. When norepinephrine-treated cells are incubated with ouabain and sufficient external sodium, the furosemide-sensitive, unidirectional influxes of both sodium and rubidium are half- maximally saturated at similar rubidium concentrations; with saturating external rubidium, the same fluxes are half-maximal at comparable levels of external sodium. In the absence of sodium, a catecholamine-stimulated, furosemide-sensitive influx of rubidium persists. In the absence of rubidium, a similar but smaller component of sodium influx can be seen. We interpret these results in terms of a cotransport model for sodium plus potassium which is activated by hypertonicity or norepinephrine. When either ion is absent from the incubation medium, the system promotes an exchange-diffusion type of movement of the co-ion into the cells. In the absence of external potassium, net movement of potassium out of the cell leads to a coupled extrusion of sodium against its electrochemical gradient.     

The Neuroleptic Chlorpromazine Inhibits the Cationic and Stimulates the Anionic Phospholipid Precursor Synthesis in Human Lymphocytes

The widely used neuroleptic drug chlorpromazine (CPZ) influences membrane functions at the levels of ionic channels and receptors as shown. Here we show the effect of short term treatments by CPZ (30 μM), on the nucleotide-containing phospholipid precursors in human lymphocyte primary cultures. During 60 minutes incubation of the cells, the CDP-ethanolamine (CDP-EA) content was only slightly reduced (87 to 76 pmol/10⁶ cells), the amount of CDP-choline (CDP-Ch) was inhibited totally (from 25 to 0 pmol) upon the treatment with 30 μM CPZ under the same conditions. It has been shown earlier, that dCTP can be used as well as CTP for biosynthesis of phospholipids. Thus, the separation of the corresponding ribo- and deoxyribo-liponucleotides was developed. CPZ almost completely inhibited the synthesis of both dCDP-EA and dCDP-Ch under the same conditions The synthesis of the activated liponucleotide precursors, can be measured by incorporation of extracellular 14C-dCyt into both dCDP-EA and dCDP-Ch, as shown earlier. While the cationic deoxyribo-liponucleotide content (dCDP-Ch, dCDP-EA) was decreased, the labelling of the anionic phospholipid precursor dCDP-diacylglycerol (dCDP-DAG) was enhanced several times, it could be labelled only in the presence of CPZ from 14C-dCyd. Thus, a principal disturbance of the membrane phospholipid synthesis is presented (i.e., inhibition of the cationic and enhancement of the anionic dCDP-DAG synthesis). This profound influence on the membrane phospholipids by chlorpromazine, might be the primary effect that contributes to the wide spectrum of CPZ effects on neuronal cells.     

Purine Nucleoside Phosphorylase Deficiency: A Mutation Update

Purine nucleoside phosphorylase (PNPase) deficiency is an autosomal recessive disorder affecting purine degradation and salvage pathways. Clinically, patients typically present with severe immunodeficiency, neurological dysfunction, and autoimmunity. Biochemically, PNPase deficiency may be suspected in the presence of hypouricemia. We report biochemical and genetic data on a cohort of seven patients from six families identified as PNPase deficient. In all patients, inosine, deoxyinosine, guanosine, and deoxyguanosine were elevated in urine, and mutation analysis revealed seven different mutations of which three were novel. The mutation c.770A>G resulted in the substitution p.His257Arg. A second novel mutation c.257A>G (p.His86Arg) was identified in two siblings and a third novel mutation, c.199C>T (p.Arg67X), was found in a 2-year-old female with delayed motor milestones and recurrent respiratory infections. A review of the literature identified 67 cases of PNPase deficiency from 49 families, including the cases from our own laboratory. PNPase deficiency was confirmed in 30 patients by genotyping and 24 disease causing mutations, including the three novel mutations described in this paper, have been reported to date. In five of the seven patients, plasma uric acid was found to be within the pediatric normal range, suggesting that PNPase deficiency should not be ruled out in the absence of hypouricemia.     

In-depth qualitative and quantitative analysis of composite glycosylation profiles and other micro-heterogeneity on intact monoclonal antibodies by high-resolution native mass spectrometry using a modified Orbitrap

Here, we describe a fast, easy-to-use, and sensitive method to profile in-depth structural micro-heterogeneity, including intricate N-glycosylation profiles, of monoclonal antibodies at the native intact protein level by means of mass spectrometry using a recently introduced modified Orbitrap Exactive Plus mass spectrometer. We demonstrate the versatility of our method to probe structural micro-heterogeneity by describing the analysis of three types of molecules: (1) a non-covalently bound IgG4 hinge deleted full-antibody in equilibrium with its half-antibody, (2) IgG4 mutants exhibiting highly complex glycosylation profiles, and (3) antibody-drug conjugates. Using the modified instrument, we obtain baseline separation and accurate mass determination of all different proteoforms that may be induced, for example, by glycosylation, drug loading and partial peptide backbone-truncation. We show that our method can handle highly complex glycosylation profiles, identifying more than 20 different glycoforms per monoclonal antibody preparation and more than 30 proteoforms on a single highly purified antibody. In analyzing antibody-drug conjugates, our method also easily identifies and quantifies more than 15 structurally different proteoforms that may result from the collective differences in drug loading and glycosylation. The method presented here will aid in the comprehensive analytical and functional characterization of protein micro-heterogeneity, which is crucial for successful development and manufacturing of therapeutic antibodies