Lectin-reactive components of the microsporidian Glugea plecoglossi and their relation to spore phagocytosis by head kidney macrophages of ayu Plecoglossus altivelis.

We investigated the reactivity of lectins to spores of Glugea plecoglossi from ayu Plecoglossus altivelis. Smear preparations of purified spores were treated with 8 kinds of lectins. Lectin blots were used to detect glycoproteins of spore lysates. In addition, lectin-treated spores were applied to head kidney macrophages of ayu, and the percentage of phagocytosis (PP) was calculated and compared with the control. Two lectins (ConA, WGA) reacted with the surface of the spores, and a major band (55 kDa) and some minor bands were visualized on blots after treatment with these. PP was decreased after ConA treatment. From these results, we suggest that G. plecoglossi spores can be phagocytized by ayu head kidney macrophages via ConA-reactive glycoprotein-mediated recognition.     

Kinetic study on the dimer-tetramer interconversion of phosphorylase b by a stopped-flow X-ray scattering method

The dimer-tetramer interconversion of phosphorylase b induced by the binding of AMP and Mg2+ was monitored using a stopped-flow X-ray scattering method. The rate constants of this second-order reaction have been determined by a nonlinear least-squares method. Burst phases in both radii of gyration and zero-angle intensities were detected at the initial step of the reaction. This suggests that rapid association might take place, followed by a slow association process of which the kinetics were measured in the present study. The radius of gyration of tetrameric phosphorylase b was determined and found to be in excellent agreement with that of phosphorylase a, but different from that of phosphorylase b reported elsewhere (G. Puchwein, O. Kratky, C. F. Golker and E. Helmreich, Biochemistry 9 (1970) 4691). The reason for this inconsistency is discussed.     

Formation of sarcoglycan complex with differentiation in cultured myocytes.

The sarcoglycan complex consists of four transmembrane protein subunits. Mutation of any one of the genes encoding these four subunits causes complete loss or marked decrease in expression of the whole complex, resulting in the phenotype of Duchenne-like autosomal recessive muscular dystrophy, termed sarcoglycanopathy. As the basis for understanding this process, we examined how the sarcoglycan complex is formed and associates with other proteins during myogenic differentiation, using a myogenic cell line. Accumulation of the sarcoglycan subunits and formation of the sarcoglycan complex were accomplished with myotube formation. In protein transport inhibition experiments with blefeldin A, we found that the sarcoglycan complex is formed in the endoplasmic reticulum and then associates with the dystroglycan complex and sarcospan en route from the Golgi apparatus to the cell surface. In early myotubes, limited kinds of incomplete sarcoglycan complexes were observed. Their analyses would provide information on the possible patterns of formation of the sarcoglycan complex.     

Preparation of a monoclonal antibody to common amino acid sequence of LHRH and its application

In order to prepare an antibody directed at the common amino acid sequence of mammalian, avian, and fish luteinizing hormone-releasing hormones (LHRHs), C-terminal free LHRH was conjugated with bovine thyroglobulin, and was used as the antigen. A monoclonal antibody (LRH13) was obtained as an ascitic fluid by fusing the spleen cells of a BALB/c donor mouse immunized with the antigen to X63.Ag8.653 mouse myeloma cells followed by limiting dilution cloning and transplanting a positive clone to BALB/c mice. This monoclonal antibody seems to belong to IgG2b as it was eluted from protein A-Sepharose CL-4B with citrate buffer pH 3.5. competitive binding experiment using fragment peptides of LHRH indicated the binding site of LRH13 was a region around serine and tyrosine, and modification of mammalian LHRH by radioiodination caused a marked decrease in the binding activity. LRH13 has an affinity constant of 0.134 X 10(9) M-1 to native mammalian LHRH, and binds C-terminal free LHRH with a similar affinity (1.6X), however, it binds with higher affinities to N- and C-terminal free LHRH (12.9X), N-terminal free LHRH (10.4X), salmon LHRH (8.3X) and chicken LHRH-I (6.0X). Chicken LHRH-II, where tyrosine is replaced for histidine, has a lower affinity (0.3X) than that of mammalian LHRH. From its high affinity to N-, C-terminal free LHRH, LRH13 is also expected to bind possible precursor peptides of LHRH. Immunohistochemical staining of the brain sections obtained from rats, mice, chickens, Japanese quail, and rainbow trout successfully visualized cell bodies and fibers distributed from the olfactory bulb to the median eminence, indicating high LHRH specificity and wide crossreactivity in animal classes of this monoclonal antibody. With this antibody, LHRH-like immunoreactive substance in the pineal gland was also stained with fixation at neutral pH.     

Analysis of phospho- and phosphonosphingolipids by high-performance liquid chromatography

A simple and efficient method for the separation of phosphosphingolipids including phosphonosphingolipids by high-performance liquid chromatography is described. A mixture of authentic lipids consisting of sphingomyelin, ceramide phosphorylethanolamine, ceramide 2-aminoethylphosphonate, and ceramide N-methylaminoethylphosphonate was completely separated using a silica gel (Zorbax SIL) column with acetonitrile-methanol-water 72:40:10 (v/v) as eluting solvent. The elution of these sphingolipids was monitored directly with an ultraviolet spectromonitor at 207 nm. The practical limit of detection of each sphingolipid was about 0.2 microgram or 0.3 nmol. Using this method, we found that from one to four different phosphono- and/or phosphosphingolipids in fresh-water shellfish can be routinely identified and reproducibly quantified.