CALCIUM ION DEPENDENCE OF THE 2-SITE IMMUNORADIOMETRIC ASSAY OF MOORE''S S-100 PROTEIN

Abstract— The two-site immunoradiometric assay (two-site IRMA) for a specific protein of the nervous system, S-100, is carried out by reaction of the S-100 protein solution with a solid-phase anti(S-100) followed by a second reaction in which the insoluble product is incubated with purified, radioactive anti(S-100). Unreacted labeled antibodies remain in solution and are washed away. As the amount of S-100 increases, the radioactivity in the solid-phase increases. The most significant assay variable is the effect of calcium on the assay dose-response. 0.1 mM-EDTA causes a total inhibition of the dose-response curve which is reversed by increasing the concentration of calcium ions. The dose-response reaches a maximum at 1.0mM-Ca²⁺. then becomes progressively inhibited as the Ca²⁺ concentration is increased further. Previous immunochemical studies of S-100 which did not allow for this effect must now be interpreted with caution.     

The effect of inorganic phosphate on sodium fluxes in dog red blood cells

The effect of extracellular inorganic phosphate on Na⁺ movements in dog red blood cells has been studied. As the phosphate concentration is increased from 0 to 30 mM, Na⁺ efflux increases by 2- to 3-fold and Na⁺ influx increases approximately 2-fold. This enhancement of Na⁺ fluxes by phosphate can be prevented by the addition of iodoacetate (1 mM), an inhibitor of glycolysis, or 4-acetamido-4′-iso-thiocyantostilbene-2,2′-disulfonic acid (0.01 mM), which blocks anion transport, to the medium. The increases in Na⁺ movements are not caused by changes in cell volumes. These results suggest that phosphate must enter the cell to enhance Na⁺ fluxes and that the mechanism of action may be via a stimulatory effect on glycolysis.     

Detection of antibodies in Brugia pahangi-infected cats by counter immunoelectrophoresis, indirect fluorescent antibody test and enzyme-linked immunosorbent assay

In cats infected with Brugia pahangi, antibodies first appeared against the larvae (L3), then against the adults (L5) and the microfilariae (mf). Homologous antigens were better than antigens prepared from heterologous species (Dirofilaria immitis, Dipetalonema viteae, Litomosoides carinii and Onchocerca gutturosa) in detecting antibodies to B. pahangi in the infected cats by indirect fluorescent antibody test (IFAT). Metabolic products of L5, but not L3 or mf, of B. pahangi were antigenic and were used in the enzyme-linked immunosorbent assay (ELISA) for detection of antibodies. Using various homologous antigens, IFAT was found to be more sensitive than counter immunoelectrophoresis and ELISA in the detection of antibodies in the infected cats. The best antigen was cryosections of L3, with a positivity rate of 81%. However, using L3, L5 and mf antigens in IFAT, a total positivity of 97% was obtained.     

Guanosine 5′-triphosphate and guanosine 5′-[βγ-imido]triphosphate effect a collision coupling mechanism between the glucagon receptor and catalytic unit of adenylate cyclase

1. GTP, but not p[NH]ppG (guanosine 5′-[βγ-imido]triphosphate), abolishes the sensitivity of glucagon-stimulated adenylate cyclase to the lipid-phase separations occurring in the outer half of the bilayer in liver plasma membranes from rat. 2. When either GTP or p[NH]ppG alone stimulate adenylate cyclase, the enzyme senses only those lipid-phase separations occurring in the inner half of the bilayer. 3. Trypsin treatment of intact hepatocytes has no effect on the basal, fluoride-, GTP- or p[NH]ppG-stimulated adenylate cyclase activity. However, ¹²⁵I-labelled-glucagon specific binding decays with a half-life matching that of the decay of glucagon-stimulated adenylate cyclase activity. 4. When GTP or p[NH]ppG are added to assays of glucagon-stimulated activity, the half-life of the trypsin-mediated decay of activity is substantially increased and the decay plots are no longer first-order. 5. Trypsin treatment of purified rat liver plasma membranes abolishes basal and all ligand-stimulated adenylate cyclase activity, and ¹²⁵I-labelled-glucagon specific binding. 6. Benzyl alcohol activates the GTP- and p[NH]ppG-stimulated activities in an identical fashion, whereas these activities are affected differently when glucagon is present in the assays. 7. We suggest that guanine nucleotides alter the mode of coupling between the receptor and catalytic unit. In the presence of glucagon and GTP, a complex of receptor, catalytic unit and nucleotide regulatory protein occurs as a transient intermediate, releasing a free unstable active catalytic unit. In the presence of p[NH]ppG and glucagon, the transient complex yields a relatively stable complex of the catalytic unit associated with a p[NH]ppG-bound nucleotide-regulatory protein.     

The reproductive behaviour ofAequidens vittatus (Pisces,Cichlidae) in Surinam,South America

Synopsis The behaviour of free-living pairs ofAequidens vittatus was observed in Surinam, South America. An ethogram of breeding behaviour is presented, based on those observations and on aquarium-held fish. This is a biparental, substrate-guarding species that spawns on a movable platform. Sexual differentiation of parental roles was more pronounced when the young were in the embryonic interval than when they were mobile juveniles. Females spent more time near their brood, attacked juvenile conspecifics more often, and fanned and mouthed embryos more than males did. Males were more involved than females in territorial spacing of pairs. The movable spawning leaf provides support for eggs on detritus substrate and may also provide protection against predators and rapid water level changes.