Distribution of pathogenic vibrios and other bacteria in imported frozen shrimps and their decontamination by gamma-irradiation.

The distribution of pathogenic vibrios and other bacteria in eight samples of imported frozen shrimps and the effect of irradiation on these bacteria were investigated. Total aerobic bacteria were at 2×10(4) to 4×10(6)/g. Coliforms consisted mainly ofEnterobacter. No salmonella were detected. A total of 66 isolates, includingVibrio parahaemolyticus, V. mimicus, V. alginolyticus, V. vulnificus, V. fluvialis and a few ofListeria monocytogenes, were obtained. The gamma-radiation dose needed to reduce by 10(-4) the number of vibrio isolates andAeromonas hydrophila was about 3 kGy in frozen shrimps, whereas about 3.5 kGy was required forL. monocytogenes.

Adsorption and elution of bovine gamma-globulin using an affinity membrane containing hydrophobic amino acids as ligands.

A hollow-fibre affinity membrane containing hydrophobic amino acids as ligands was prepared by the radiation-induced grafting of glycidyl methacrylate onto a porous polyethylene hollow fibre and subsequent phenylalanine (Phe) or tryptophan (Trp). The densities of the Phe and Trp ligand of the resulting affinity membrane were 0.4 and 0.4 mol/kg, respectively. The Trp-containing affinity membrane exhibited a higher amount of adsorbed bovine gamma-globulin (BGG) than the Phe-containing membrane. To evaluate the adsorption behaviour of the membrane, the BGG-containing buffer solution was permeated from the inside to the outside of the Trp-containing hollow-fibre affinity membrane through the ligand-immobilized pores. The breakthrough curves as a function of effluent volume coincided irrespective of the flow-rate, i.e. the residence time (55-220 s) of the solution across the membrane (thickness 0.83 mm), as a result of negligible mass transfer resistance. A series of chromatographic procedures, (adsorption-washing-elution) was repeated twice and a satisfactory quantitative elution was attained. The reproducible profile of the flux and the protein concentration assured a quantitative cycle of chromatography using the affinity membrane containing Trp as a ligand.

Inhibition of atrial natriuretic peptide-induced cyclic GMP accumulation in the bovine endothelial cells with anti-atrial natriuretic peptide receptor antiserum.

Using an antiserum raised against the purified atrial natriuretic peptide (ANP) receptor that has a disulfide-linked homodimeric structure and represents one subtype of the multiple ANP receptors, we showed that the receptor is coupled to the guanylate cyclase activation; formerly, this type of ANP receptor is not considered to be coupled to the cyclase. The specificity of the antiserum was determined by immunoblot analysis and immunoprecipitation. The anti-receptor antiserum did not compete with 125I-ANP for binding to the receptor but it lowered the affinity of the receptor. When added to bovine endothelial cell cultures, the antiserum blocked the cyclic GMP response of the cells triggered by ANP. These results indicate that the subtype of the ANP receptor recognized by the antiserum is responsible for the activation of particulate guanylate cyclase as well as the double function type receptor that has been assumed to contain both the receptor domain and the catalytic domain for cGMP synthesis on the same molecule. The presence of dissociative complexes of ANP receptor and particulate guanylate cyclase was also demonstrated by radiation inactivation analysis.

Mechanism of activation of particulate guanylate cyclase by atrial natriuretic peptide as deduced from radiation inactivation analysis.

The interaction between the receptor (Rc) for atrial natriuretic peptide (ANP) and the effector enzyme particulate guanylate cyclase (GC) has been studied by radiation inactivation. Irradiation of bovine lung membranes produced an increase in GC activity at low radiation doses followed by a dose-dependent reduction at higher doses. This deviation from linearity in the inactivation curve disappeared when lung membranes were pretreated with ANP. Essentially identical results were also obtained with adrenal membranes. Based on these radiation inactivation data, the following dissociative mechanism of activation of particulate guanylate cyclase by ANP has been proposed: Rc.GC(inactive) + ANP----Rc.ANP + GC(active).

Functional molecular size of trypsin inhibitors as determined by radiation inactivation analysis.

The molecular sizes of trypsin inhibitors obtained by radiation inactivation were investigated in relation to the functional domain size. The molecular weights obtained were 10,200 +/- 700 for ovomucoid, 17,800 +/- 400 for ovoinhibitor and 16,400 +/- 500 for soybean trypsin inhibitor. These values mostly agreed with the size of domain which has trypsin inhibitory activity, suggesting that the radiation inactivation analysis indicates the minimum functional domain size.