Mannose-specific oligosaccharide recognition by mononuclear phagocytes

Glycoproteins terminating in mannose are recognized by receptors on macrophages. The mannose receptor is expressed by a variety of macrophages but expression is closely regulated. Activated macrophages, for example, express little mannose receptor activity. Kinetic and fractionation experiments suggest that cell surface mannose receptors recycle to and from an acidic, pre-lysosomal compartment. Preliminary evidence suggests that the mannose receptor is a large polypeptide and that it is structurally related to the mannose binding protein found in serum. The mannose receptor may, among other possibilities, regulate the extracellular levels of lysosomal hydrolases.     

The in situ assay of Candida albicans enzymes during yeast growth and germ-tube formation

Conditions are described for the preparation of permeabilized cells of Candida albicans. This method has been used for the in situ assay of enzymes in both yeast cells and germ-tube forming cells. A mixture of toluene/ethanol/Triton X-100 (1:4:0.2, by vol.) at 15% (v/v) and 8% (v/v) was optimal for the in situ assay of glucose-6-phosphate dehydrogenase in yeast and germ-tube forming cells, respectively. The concentration of toluene/ethanol/Triton X-100 required for optimal in situ activity of other enzymes was influenced by the cellular location of the enzyme, growth phase and morphology. The membrane-bound enzymes (chitin synthase, glucan synthase, ATPase), cytosolic enzymes (glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase, pyruvate kinase, phosphofructokinase, alkaline phosphatase, glucosamine-6-phosphate deaminase and N-acetylglucosamine kinase) and wall enzymes (beta-glucosidase and acid phosphatase) were measured and compared to the activity obtained in cell extracts. The pattern of enzyme induction and the properties of the allosteric enzymes phosphofructokinase and pyruvate kinase were measured in situ. Pyruvate kinase in situ was homotropic for phosphoenolpyruvate with a Hill coefficient of 1.9 and a S0.5 of 0.6 mM, whereas in cell extracts, it had a Hill coefficient of 1.9 and a S0.5 of 1.0 mM. The Km for ATP was 1.6 mM in cell extracts and 1.8 mM in permeabilized cells. In situ phosphofructokinase was homotropic for fructose 6-phosphate (S0.5 of 2.3 mM, Hill coefficient of 4.0). The kinetic properties of pyruvate kinase and phosphofructokinase measured in situ or in vitro were similar for both yeast cells and germ-tube forming cells.     

Subpopulations of apolipoprotein A-I in human high-density lipoproteins. Their metabolic properties and response to drug therapy

In this study immunological procedures were used to detect and quantify high-density lipoprotein (HDL) particles of differing apolipoprotein A composition. In the plasma of eight healthy female subjects, 45% of the total apolipoprotein A-I existed in particles (called '(AI)HDL') devoid of apolipoprotein A-II. The remainder circulated in association with apolipoprotein A-II at a molar ratio of approximately 1:1. Nicotinic acid selectively raised the plasma apolipoprotein A-I/A-II ratio by increasing the proportion of (AI)HDL particles. Probucol produced the opposite effect, lowering the plasma concentration of these particles. The kinetic properties of apolipoprotein A-I in total HDL and in the (AI)HDL particle were the same despite the fact that apolipoprotein A-I equilibration between these two species was incomplete. Therefore, there appear to be at least two apolipoprotein A-containing particle populations in HDL which are immunochemically and metabolically distinct.     

A single-blind, placebo-controlled comparison of the reactivity and antigenicity of trivalent oral poliomyelitis vaccine prepared in monkey kidney or human diploid cell substrates

Vaccination with a single dose of trivalent oral poliomyelitis vaccine elicited fourfold or greater antibody responses to one or more poliomyelitis virus types in 59% of volunteers (16/27) receiving vaccine prepared from virus grown in monkey kidney cells and in 69% of volunteers (16/23) receiving vaccine prepared from virus grown in MRC5 human diploid cells. Type for type the antibody titres and percentages of volunteers responding to the two vaccines were broadly equivalent. The clinical reactivities of both vaccines were similar to that of a placebo in terms of the overall incidence, duration and severity of reactions. The nature of the reactions observed did, however, vary, in that headaches were more frequently reported by recipients of vaccine prepared from virus grown in monkey kidney cells. This difference was not, however, statistically significant.     

The sequence of the bacteriophage P1 genome region serving as hot target for IS2 insertion.

A restriction fragment of the bacteriophage P1 genome known to serve as a hot target for IS2 insertion in its host, Escherichia coli K12, was entirely sequenced. It is 1756 bp long and it contains four long open reading frames, all in the same orientation. The two middle frames overlap partially. Eight of the nine studied IS2 insertions affecting phage reproduction map within three of these reading frames. No common feature was found between the nine target sites which have served for IS2 integration. However, there are two structural elements which might possibly contribute to rendering the studied DNA segment a hot region for IS2 insertion. The first is formed by two neighbouring, 30 and 40 bp regions of homology with an internal segment of IS2. The second is the pentanucleotide 5' GGTAT3', which is carried nine times in the sequenced fragment and which is found always in at least one copy within a variable distance of less than 100 bp of each inserted IS2 element.     

Gratuitous induction by N-acetylmannosamine of germ tube formation and enzymes for N-acetylglucosamine utilization in Candida albicans.

N-Acetylmannosamine did not support the growth of Candida albicans, and this sugar was not accumulated by cells. Incubation of starved yeast cells at 37 degrees C with N-acetylmannosamine plus glucose resulted in germ tube formation. Furthermore, N-acetylmannosamine alone induced the uptake system for N-acetylglucosamine and the enzymes of the N-acetylglucosamine catabolic pathway to the same extent as the natural substrate. Induction of the uptake system and the enzymes was observed at 28 degrees C without germ tube formation and at 37 degrees C with germ tube formation. N-Acetylmannosamine is thus a gratuitous inducer for enzymes of the N-acetylglucosamine pathway and germ tube formation in C. albicans.     

Circular mitochondrial DNA molecules from petite mutants of Saccharomyces cerevisiae: resolution by polyacrylamide gel electrophoresis

Mitochondrial DNA (mtDNA) from petite strain K45 ofSaccharomyces cerevisiae contains about 7% circular DNA molecules which comprise a simple oligomeric series based on a monomeric size of 1.7 kilobase pairs. Electrophoresis of K45 mtDNA on a polyacrylamide-agarose slab gel fractionates the mtDNA into a major band (containing linear DNA) and several faster running minor bands each containing particular size class of circular DNA molecules. From study of mtDNA from K45 and two other simple petites it was found that the mobility of circles is inversely proportional to the logarithm of the circle size. Polyacrylamide gel electrophoresis thus permits the separation of circular mtDNA from the linear mtDNA of simple petites, and physically resolves circles of different size from one another.     

Electron spin resonance studies of the solution structure of vanadyl amino acid complexes and mixed ligand complexes of oxalate.

Esr and electronic spectra of complexes of the general composition VO(AA)2 and VO(ox)(AA) have been characterized; AA = gly, his, cys, pro, val, met, asp amino acids. Spectra of the formulation VO(ox)(LL) (with LL = imidazole plus monodentate oxalate, histamine plus monodentate oxalate, histidine, cysteine, 4-imidazolepropionic acid, mercaptopropionic acid, ethylenediamine and ethanolamine) have been used to deduce a self-consistent assignment of AL, a ligand donor additivity constant contribution to the observed hyperfine splitting, Aiso. Values of AL are sensitive to inductive effects in the ligand structure. The solution structures and likely coordination geometries of VO(his)2, and VO(cys)22-- are discussed. The role of the imidazole moiety as a sigma donor and sulfhydryl sulfur as a pi acceptor is observed in VO(AA)2 and VO(ox)(AA) complexes.     

A comparison of two methods to investigate the metabolism of human apolipoproteins A-I and and A-II.

Two methods are compared for measuring the kinetic parameters of apolipoprotein A-I and A-II metabolism in human plasma. In the first, high density lipoprotein apoproteins were radioiodinated in situ in the lipoprotein particle (endogenous apoprotein labeling) while in the second, individually labeled apolipoprotein A-I or A-II was incorporated into the particle by in vitro incubation (exogenous apoprotein labeling). The catabolic clearance rate of exogenously labeled apolipoprotein A-I was consistently faster than that of endogenous apolipoprotein A-I. Conversely, endogenously and exogenously labeled apolipoprotein A-II were catabolized at identical rates. The fractional plasma clearance rates of endogenous apolipoproteins A-I and A-II were the same.