Schistosoma mansoni, NIH-Sm-PR-2 strain, in non-susceptible Biomphalaria glabrata: protection by Echinostoma paraensei

Sullivan J. T., Richards C. S., Lie K. J. and Heyneman D. 1981. Schistosoma mansoni, NIH-Sm-PR-2 strain, in non-susceptible Biomphalaria glabrata: Protection by Echinostoma paraensei. International journal for Parasitology11:481–484. Among seven inbred genetic stocks of Biomphalaria glabrata that are non-susceptible for the NIH-Sm-PR-2 strain of Schistosoma mansoni (PR-2), five stocks revert to nearly complete susceptibility when first infected with Echinostoma paraensei. These include both stocks in which PR-2 sporocysts are normally destroyed within 3–7 days, and stocks in which sporocysts often survive undeveloped for at least 3 weeks. Hence, these five stocks are resistant to but physiologically suitable for the development of PR-2. Of the two remaining stocks, one remains partly non-susceptible to PR-2, since less than 50 % of echinostome-infected snails revert to susceptibility, while the other stock remains completely non-susceptible to PR-2 following echinostome infection, due perhaps to a high level of residual resistance and/or unsuitability.     

Kinetics of drug-DNA interaction. Dependence of the binding mechanism on structure of the ligand

Kinetic and equilibrium studies of the binding of several phenanthridines and acridines to DNA have been performed to investigate the physical processes underlying the direct ligand transfer mechanism of drug-DNA interaction· Substitution of the 6-phenyl ring of dimidium with a p-carboxyl residue, or complete removal of either the 6-substituent or the 3-amino group, does not prevent the phenanthridine chromophore from transferring directly between binding sites. Loss of the aromatic ring increases association rate constants three- to ninefold and enhances dissociation rates by factors of up to 12; the rates of direct transfer and dissociation from site 1 are the most perturbed. The presence of a phenyl ring stabilizes the site 1 complex and lowers the binding constant to site 2. Introduction of the p-carboxyl group does not affect the equilibrium distribution of bound forms but produces equivalent increases (2·5-fold) in forward and reverse rate constants for binding to site 1 and for the direct transfer step. The 3-amino group greatly stabilizes the site 1 complex. Its removal accelerates all kinetic processes except for the reverse transfer step; the transfer rate is enhanced 25-fold and binding to site 2 is increased 12-fold. The dissociation rate from site 1 rises by a factor of 45 and that from site 2 by a factor of 5·8.10-Methyl-9-aminoacridine binds via the direct transfer pathway with rate and equilibrium constants similar to those of the 3-desamino derivative of ethidium. This compound provides the first fully characterized example of an acridine that utilizes bimolecular transfer. By contrast, rivanol (6,9-diamino-2-ethoxyacridine) interacts with DNA via a two-step sequential mechanism analogous to that seen with proflavine, yet its intrinsic association constant is three times higher. This results from tighter ‘external’ attachment to the helix, together with a decrease in equilibrium constant for the insertion step, which is markedly slower than that of proflavine. There appears to be a simple relation between the apparent enthalpy of binding and the number of extracyclic amino substituents on the intercalating chromophore.We propose that the two bound forms that participate in direct ligand transfer represent molecules intercalated via one or other of the grooves of DNA, and that the transfer pathway corresponds to exchange of drug between the wide groove of one helix and the narrow groove of another. The ability to form strongly bound complexes at the surface of the helix appears to play a major role in determining the mechanism of ligand binding.     

Role in hemolysis of the interaction of tellurium compounds with glutathione

We have shown that tellurite and tellurate require the interaction with reduced glutathione (GSH) to hemolyze human erythrocytes. The study of the nature of this interaction is the main object of this paper. The degree of hemolysis was determined by the method of Angelone. The addition of extracellular 1 mM GSH or cysteine increased the rate of hemolysis. Concanavalin A (0.3 mg/mL) and/or 4 mg/mL adenosine did not affect the hemolysis by 0.1 mM tellurite. One tenth to 1 mM 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonate (SITS) inhibited this hemolysis by 60–100%. Millimolar GSH released this inhibition. Incubation of 0.1 mM tellurite with 1 mM GSH for 90 min at 37°C, produced a hemolytic agent when prepared and tested under nitrogen, but one that was not active when prepared in air. The hemolysis byp-hydroxymercuribenzoate orp-hydroxymercuriphenylsulfonate did not involve GSH. Scanning electron micrographs showed a sphero-echinocyte transformation, in the pre-hemolytic stage, with all the agents tested. The rate of penetration of tellurite plays a role in determining the rate of hemolysis, as shown by the effect of SITS. The release by GSH of the inhibition by SITS poses questions concerning the site of action and cell membrane penetration of the hemolytic agent. Telluride or some intermediate in the interaction of GSH with tellurite is the actual hemolytic agent.     

A model for population regulation with density- and frequency-dependent selection

The life-cycle of a species with separate generations is divided into a reproduction phase and a growing-up phase. In the reproduction phase we assume random mating and selection due to genotype differences in fecundity of the parents and viability of the offspring. During the growing-up phase we assume a (deterministic) death process in continuous time with death rates for the genotypes which increase linearly with the genotype population sizes.In the absence of genotype differences the model gives logistic population regulation. With genotype differences the model generalizes the usual separate generations selection patterns. In addition to these we exhibit cases with three polymorphic equilibria or with a stable cycle.     

Electrokinetic study of the reactions of peritoneal macrophages and eosinophils with IgG immune complexes

Electrophoretic light scattering (laser Doppler electrophoresis) has been employed to study the effects of guinea pig IgG immune complexes on the electrophoretic mobility distributions of guinea pig resident peritoneal cells. The resident population of cells is composed of macrophages (approximately 75%) and eosinophils (approximately 25%). These cells were separated according to the well-established method of Boyum. Populations of resident macrophages, eosinophils, and the unfractionated samples were incubated with soluble immune complexes, antigen alone, or antibody alone. The mean mobility of the resident macrophages decreased approximately 60% when incubated in the presence of immune complexes, although no effect could be discerned in the presence of antigen or antibody alone. The width of the resulting macrophage mobility distribution was larger than that of the control distributions, with a broad shoulder on the high-mobility side, indicating a heterogeneous response of the macrophages to the immune complexes. Eosinophils react in two distinct fashions. One population of eosinophils is present near the control experiments. The second population reacts in a manner very similar to that of macrophages. This suggest that at least two populations of eosinophils are present in the unstimulated guinea pig peritoneal cavity. Results that are intermediate between these two cases are found when unfractionated samples are studied.     

Rapid determination of chain length pattern in poly(ADP-ribose) samples

(³H)poly(ADP-ribose) synthesized from nuclei by incubation with (³H)NAD was released from protein by alkaline treatment and electrophoresed in dodecyl sulfate gels. Individual polymers up to at least 33 units were completely separated according to their chain length. Size distribution was visualized by fluorography of the gels, and quantified by radioactivity determination of sliced gels The method could be applied to crude nuclear extracts. It showed that nuclei of Ehrlich ascites tumor cells produced a poly(ADP-ribose) pattern distinctly different from that of rat liver nuclei.     

Boophilus microplus: characterization of larval proteases.

Cercariae of Schistosoma mansoni were treated with undecenyl-pseudothiourea. After centrifugation, they agglutinated into a mass. Resuspended in water, they remained immobilized. When injected sub-cutaneously into mice, they produced bisexual infections. The immobilizing drug effect, together with a reduced worm recovery rate, are time and concentration dependent. The cercariae become avirulent (99.8%) only when the flame cell is affected. Immobilizing and “cercaricidal” effects are not necessarily related properties; the latter can be determined only by in vivo tests of infectivity. No protection against reinfection was noticed in mice injected with immobilized cercariae of reduced virulence. The immobilized cercariae produced infections with a 0.7% worm recovery rate by percutaneous exposure, compared to 2.2% by subcutaneous injection. Normal cercariae produced infections with average recovery rates of 11.1% subcutaneously and 45% percutaneously.     

Separation of two HMM-S1 species from white muscle myosin

Heavy meromyosin subfragment 1 was resolved by chromatography on DEAE-cellulose into two fractions characterized by the nature of the alkali light chains present. It was shown that even in an HMM-S1 preparation with an extensive fragmentation of the heavy chain a polyacrylamide gel electrophoresis analysis differentiates alkali light chains among the light fragmentation components. A non-fragmented HMM-S1 was obtained from a papain digest of myofibrils and the chromatographic analysis supplied further evidence of the separation of the two species of HMM-S1 present in rabbit white muscle myosin.