Influence of praziquantel and Ca2+ on the bilayer-isotropic-hexagonal transition of model membranes

Praziquantel induces a bilayer to isotropic transition in the absence of Ca2+ in a mixed phospholipid membrane consisting of phosphatidylethanolamine (PE) and phosphatidylserine (PS) at a molar ratio of 2:1 at 25 degrees C or 35 degrees C, irrespective of the lipid/drug molar ratio (10:1; 2:1). Addition of Ca2+ at different PS/Ca2+ molar ratios (4:1, 2:1 or 1:1) leads to a transition to a hexagonal (HII) state. With a phospholipid membrane of different composition (PE/PS molar ratio 4:1) praziquantel exerts quite different effects in the presence of Ca2+ (PS/Ca2+ molar ratio 1:1). An isotropic-signal appears together with a bilayer one at 25 degrees C, while a HII-signal can be detected at 35 degrees C. Thus, two separate phases coexist at this PE/PS molar ratio, while at a PE/PS molar ratio of 2:1, praziquantel and Ca2+ induce only a HII-signal. The results with these model membranes show that praziquantel and Ca2+ exert drastic influences on bilayer-isotropic-hexagonal transitions. The possibility that this drug might act in the schistosomal tegumental membranes in the same way is discussed.

Genetic and fossil evidence for the origin of modern humans

The origin of living Homo sapiens has once again been the subject of much debate. Genetic data on present human population relationships and data from the Pleistocene fossil hominid record are used to compare two contrasting models for the origin of modern humans. Both genetics and paleontology support a recent African origin for modern humans rather than a long period of multiregional evolution accompanied by gene flow.

Conformation-activity relationships of opiate analgesics

Extensive conformational calculations were performed on the potent opiate analgesics etorphine, PET, R30490 and etonitazene to determine all of their many low-energy conformations. The results were used to characterize four possible models for binding of a simple pharmacophore, comprising two phenyl rings plus a protonated nitrogen, to opiate analgesic receptors. These four models may define the necessary three-dimensional features leading to particular opiate actions. The model favoured for mu receptor activity can accommodate a protonated nitrogen, an aromatic ring (which may be substituted with an electronegative group) and a second lipophilic group. These structural features must be presented in a precise three-dimensional arrangement. It appears likely that a hydrophilic substituent in a certain region of the analgesic pharmacophore may also interact with the receptor as a secondary binding group.

Praziquantel impairs the ability of exogenous serotonin to stimulate carbohydrate metabolism in intact Schistosoma mansoni

Praziquantel (PZQ) (Droncit, Biltricide) at 10 microM completely abolishes the stimulatory effect of serotonin on glucose uptake and lactate excretion of Schistosoma mansoni. Fluoxetine (FXT) exerts similar effects on the serotonin-induced stimulation of glucose uptake and lactate excretion, however, at 100-fold higher concentrations. In comparison with PZQ, which is inhibitory at 10 microM, FXT and other amphiphilic cationic drugs (amitriptyline, propranolol, imipramine, chlorpromazine) inhibit glucose uptake or lactate excretion in schistosomes at 1 mM; the strongest inhibitor is FXT. Glycogen breakdown is maximally stimulated by PZQ in the absence or presence of serotonin. There is an additive effect of 50 microM chlorpromazine or FXT and 0.01 to 0.1 microM PZQ on glycogen breakdown. The rate of sodium-sensitive or insensitive serotonin uptake in Schistosoma mansoni is reduced by 10 microM PZQ by about 40%, as is the sodium-sensitive excretion of serotonin. The results show that PZQ interferes with the ability of serotonin to stimulate carbohydrate metabolism. The possibility that PZQ may act through an effect on tegumental integrity is discussed.

Chlorpromazine, other amphiphilic cationic drugs and praziquantel: effects on carbohydrate metabolism of Schistosoma mansoni

The effects of the amphiphilic cationic drugs chlorpromazine, imipramine, amitriptyline, propranolol and fluoxetine and praziquantel were investigated on glucose uptake and lactate excretion of Schistosoma mansoni. While praziquantel enhances glucose uptake and lactate excretion at a concentration of 10(-7) M, all the other drugs exert the same effects at concentrations above 10(-5) M. Generally, a constant molar ratio of 1:2 is found between glucose uptake and lactate excretion. Above 10(-5) M, praziquantel inhibits glucose uptake and lactate excretion. Similar effects are caused by amphiphilic cationic drugs at 10(-3) M. Pre-incubation of S. mansoni with 10(-5) M praziquantel completely abolish the stimulation of carbohydrate metabolism by serotonin and by 5 X 10(-5) M chlorpromazine or fluoxetine. The action of praziquantel on S. mansoni resembles that of amphiphilic cationic drugs with respect to their influence on carbohydrate metabolism. This, together with data obtained from electrophysiological and electron microscopic studies, provides evidence for the hypothesis that praziquantel exerts its effect by interacting with membrane structures.

Antibody to liver membrane antigens in chronic active hepatitis. IV. Exclusion of specific reactivity to polypeptides and glycolipids by immunoblotting

The reactivity of sera was examined in patients with autoimmune chronic active hepatitis and other liver diseases by immunoblotting. Polypeptides and glycolipids of liver plasma membrane, liver-specific lipoprotein and kidney membrane were separated and probed with sera from patients and from a rabbit immunized with mouse liver plasma membrane. Chronic active hepatitis sera reacted with a number of polypeptides in the liver plasma membrane preparations; similar but weaker reactivity was observed with sera from patients with other diseases and in some healthy subjects. Chronic active hepatitis sera did not react with glycolipids from liver plasma membrane. The immune rabbit serum reacted with two polypeptides of 180 kd present in liver plasma membrane but absent from kidney membrane, with two polypeptides of 50 kd which were nonliver-specific but species-specific, and with three major glycolipid components of liver plasma membrane: this reactivity thus differed markedly from that of the chronic active hepatitis sera. In studies using dot-blotting, it was found that solubilization of liver plasma membrane in detergents resulted in a marked reduction of the reactivity to liver plasma membrane of chronic active hepatitis sera, but little change in the reactivity of the chronic active hepatitis and other sera with liver-specific lipoprotein by immunoblotting indicated that liver-specific lipoprotein consisted of constituents of liver plasma membrane together with intracellular proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of praziquantel on human intestinal flukes (Fasciolopsis buski and Heterophyes heterophyes)

Human intestinal flukes (Fasciolopsis buski and Heterophyes heterophyes) were treated with praziquantel in vivo or in vitro and then studied by transmission (TEM) and scanning (SEM) electron microscopy. F. buski worms recovered from patients, which had been cured by oral treatment of 1 X 15, 1 X 25 or 1 X 40 mg praziquantel/kg body weight, showed typical contraction and alterations together with vacuolization and bleb formation of their tegument. H. heterophyes worms recovered from an experimentally infected dog were incubated in media containing 1 microgram praziquantel/ml for 5-60 min. Their tegument showed lesions the extent and duration of which increased with exposure time, finally leading to death. The damage observed in vitro was very similar to that found in F. buski recovered from cured patients. The cure rate was very high when using 1 X 15 mg praziquantel/kg.

Dose-titration of fenbendazole in the treatment of poultry nematodiasis

Broiler chickens were fed ad libitum diets containing fenbendazole at various concentrations and durations for the removal of adult Ascaridia galli, Heterakis gallinarum, and Capillaria obsignata. All regimens were 100% effective against A. galli. Fenbendazole at doses of 80 ppm for 3 days and 48 or 30 ppm for 5 days was 100% effective against H. gallinarum. C. obsignata was not removed completely by any regimen, but greater than or equal to 95% effectiveness was seen in birds given fenbendazole at doses of 80 ppm for 3 days and 48 ppm for 5 days. All medicated rations were readily consumed, and the treated birds exhibited no adverse reactions.

Purification of the fructose 1,6-bisphosphate-dependent lactate dehydrogenase from Streptococcus uberis and an investigation of its existence in different forms

The fructose 1,6-bisphosphate [Fru(1,6)P2]-dependent lactate dehydrogenase in cells of Streptococcus uberis N.C.D.O. 2039 was purified by a procedure that included chromatography on DEAE-cellulose and Blue Sepharose CL-6B in phosphate buffers. The enzyme appeared to interact with Blue Sepharose through NADH-binding sites. The homogeneous enzyme had catalytic properties that were generally similar to those of other Fru(1,6)P2-dependent lactate dehydrogenases, and it had no catalytic activity in the absence of Fru(1,6)P2. Its existence in different forms, depending on conditions, was investigated by ultracentrifugation, analytical gel filtration and activity measurements. It consisted of subunits with Mr 35,900 +/- 500 and, in the presence of adequate concentrations of Fru(1,6)P2, phosphate or NADH, it existed as a tetramer, whereas when these ligands were in lower concentrations or absent, the subunits were in a concentration-dependent association-dissociation equilibrium. Dissociation occurred slowly and inactivated the enzyme, and although added ligands reversed the dissociation, the lost activity was at best only partly restored. An exception occurred when dissociation was caused by a decrease in temperature, in which case the lost activity was fully restored at the original temperature. The tetramer also lost activity at certain ligand concentrations without dissociating. The results together indicated the presence on the enzyme of two classes of binding site for both Fru(1,6)P2 and NADH, and the likelihood that phosphate bound at the same sites as Fru(1,6)P2. Two different ligands together were much more effective at preventing inactivation and dissociation than was expected from their effectiveness when present separately. It was concluded that tetrameric forms of the enzyme rather than the enzyme in association-dissociation equilibrium were involved in the regulation of its activity in vivo.

A new approach for detection and assignment of disulfide bonds in peptides

A new procedure is described for identification of disulfide bonds in peptides by fast atom bombardment mass spectrometry (FABMS). Prolonged bombardment of a disulfide-containing peptide in solution by a high-energy xenon beam results in gradual reduction of the disulfide bond. The reduction is the result of reaction intermediates initially produced by the xenon beam. The method for characterization of interchain disulfide bonds is based on the increase in the relative intensity of the pseudomolecular ions of the reduced peptides with a simultaneous decrease in the relative intensity of the protonated molecular ion of the oxidized peptide. This information allows one to identify peptide fragments covalently linked via intermolecular disulfide bonds. The intrachain disulfide bonds are identified by the increase in the relative intensity of the protonated molecular ion of the reduced peptide, relative to the intensity of the protonated molecular ion of the oxidized peptide. These results indicate that this method can be used to detect disulfide bonds of peptides and provides unambiguous information regarding disulfide bond assignment in peptides. Approximately 1 nmol of sample is required.

Histology of adult Litomosoides carinii (Nematoda: Filarioidea)

The histology of male and female Litomosoides carinii was studied in serial sections. The body wall of the female worm consists of a rather thin cuticle, very extended lateral hypodermal chords and small sectors of shallow coelomyarian muscle cells. In the female worm an intestinal lumen is found, which is filled with material throughout the worm's length. Both ovaries are situated close to the posterior end. In both genital tubes all stages of oogenesis and embryogenesis could be observed in approximately equal stages of development in most of the sections. The lateral chords of the male worm are very small, whereas the somatic muscle cells are large and of the circomyarian type. The intestine is a minute tube beside the much thicker testis and vas deferens. Considerable sexual dimorphism could be observed in almost all organs of adult Litomosoides carinii.

Fine structure of adult Litomosoides carinii (Nematoda: Filarioidea)

The fine structure of the body wall and the intestine of male and female Litomosoides carinii was studied in sections through the middle and posterior regions of the worms. In the sublateral cells of the female hypodermis the organelles are arranged in regular layers. The zone with the basal labyrinth is the most prominent layer. The intestinal epithelium of the female worm varies considerably in thickness. The cytoplasm of these cells contains many large droplets. The lateral hypodermal chords of the male worm are very narrow bands. The muscle cells of the male worm are of the circomyarian type, without an afibrillar portion. The intestinal lumen of the male worm is very narrow, and the epithelial cells contain very large droplets. In both sexes the hypodermis contains bacteria. Larger glycogen deposits were absent in the hypodermal chords and in the muscle cells of the midbody regions.

Zonal unit-gravity elutriation. A new technique for separating large cells and multicellular complexes from cell suspensions

A new and simple technique, zonal unit-gravity elutriation, has been devised for separating very large cells, multicellular complexes, or small organisms from suspensions consisting mainly of small cells. The separation vessel is a conical chamber with an entrance at the lower, narrower part of the cone and an exit at the upper, wider part of the cone via a dome-shaped lid. A baffle at the entrance prevents turbulence from incoming fluid. Chambers of differing widths and wall slopes are chosen depending on the sedimentation rate of the particles to be separated. A small volume of the cell suspension is placed in the chamber on the bench in a cold-room. Medium stabilized by a shallow density gradient is pumped into the base of the chamber and ascends, creating a decreasing velocity gradient. Cells sediment at unit-gravity against this ascending counterstream, and are separated into bands according to sedimentation velocity. By adjusting the flow rate of the medium, different sizes of cells can be separated. Tumor cells can be enriched, and larger blast cells can be separated from small cells in lymphoid cell suspensions. The procedure produces complete separation of thymic nurse cells (epithelial-lymphoid complexes) from free thymocytes in digested thymus suspensions and produces substantial enrichment of thymic rosettes (macrophage-lymphoid complexes). A very favorable situation for applying this technique is the isolation of Taenia taeniaformis larvae, which can be completely purified from infected liver suspensions, representing a 4 X 10(5)-fold enrichment of the parasites, with high recovery, in a single 30 min operation.

The limited immunocompetence of thymocytes within murine thymic nurse cells

Thymic nurse cells, cortical epithelial cells enclosing 20-200 lymphocytes, were prepared from mouse thymus by enzyme digestion and repetitive sedimentation. Individual nurse cells were then isolated free of any exogenous thymocytes by micromanipulation, and the endogeneous thymocytes released from inside the nurse cells by a brief period of culture. The thymocytes from within individual nurse cells were tested, at the one cell/well level, for their capacity to proliferate in high cloning efficiency mitogen-stimulated limiting dilution cultures. The resultant clones were tested for their cytolytic capacity in a lectin-mediated isotype-release assay. Most intra-nurse cell thymocytes were unresponsive, like typical cortical thymocytes, but an average of 1/30, or around 2-6 lymphocytes/nurse cell, were able to proliferate in response to concanavalin A. The clones produced were of a relatively small size, similar to those characteristic of helper-lineage T cells. No cytolytic clones at all were obtained, despite stringent positive controls showing an efficient cytolytic response from known sources of cytolytic precursor cells. This finding disagrees with earlier studies on nurse cell lymphocytes, where there may have been a possibility of contamination with exogenous thymocytes. These results suggest either that the nurse cell represents a selective environment for helper-lineage T cell differentiation, or that further steps after the nurse cell stage are needed to produce mature cytolytic-lineage T cells.

Are any functionally mature cells of medullary phenotype located in the thymus cortex?

Experiments were undertaken to test if thymocytes of "mature" or "medullary" phenotype were restricted to the medullary area of the thymus. A calculation based on direct cell counts on serial sections indicated that 11.5% of adult male CBA thymic lymphoid cells were within the medullary zone. Since only 3-4% of thymocytes were cortisone resistant, the majority of thymocytes within the medulla were, like cortical thymocytes, cortisone sensitive. A series of cell surface antigenic markers, used alone or in pairs, suggested that 13-15% of thymocytes were of medullary phenotype, somewhat more than the number of thymocytes actually present in the medulla. However, much of this discrepancy could be explained by differential death of cortical cells during isolation and staining, and by the existence in the cortex of a subpopulation of early blast cells which shared some, but not all markers with medullary thymocytes. A direct test for mature or medullary phenotype cells in the cortex involved selective transcapsular labeling of outer-cortical cells with fluorescent dyes, followed by multiparameter immunofluorescent analysis of the 10% labeled population. Outer-cortical thymocytes included some cells (mainly early blasts) sharing some markers with medullary thymocytes, but very few (less than 1%) of these cells expressed all the characteristic "mature" markers. Limit-dilution precursor frequency studies showed the level of functional cells in the outer cortex was extremely low. The overall conclusion was that the vast majority of cells of complete "mature" phenotype are confined to the thymic medulla. These findings favor the view that thymus migrants originate from the thymic medulla, but do not exclude a cortical origin. The results also illustrate the need for multiparameter analysis to distinguish medullary thymocytes from early blast cells.

Identification of a structure on human melanoma cells recognized by CTL exhibiting anomalous killer cell function

The structures involved in the recognition of melanoma cells by nonspecific cytotoxic T lymphocytes (CTL) activated in mixed lymphocyte culture were investigated with monoclonal antibodies (MAb) which blocked this anomalous killer (AK) function. Of over 2000 MAb raised against melanoma cells, only three inhibited killing; one of these, an IgMk termed Leo Me13, was investigated in detail. In antibody-binding studies using a large range of cultured tumor cells, it was shown that Leo Me13 was relatively specific for melanoma cells. Of more importance, Leo Me13 inhibited conjugate formation between AK cells and melanoma target cells by 60 to 80% and caused an eight- to 10-fold reduction in killing. The MAb did not immunoprecipitate protein from melanoma cells surface-labeled with 125I, and thin-layer chromatography followed by immunoblotting of the separated glycolipids from melanoma cells indicated that the epitope was on acidic glycolipids migrating between GM1 and GD1a; moreover, treatment of melanoma cells with neuraminidase resulted in complete loss of binding of Leo Me13 but not of other anti-melanoma antibodies which did not inhibit AK cell-mediated lysis. Other melanoma-reactive MAb of the same isotype as Leo Me13 did not block killing of melanoma cells, but one documented antibody, R24, an IgG3 with specificity for the ganglioside GD3, was found to inhibit this function. These data suggest that the AK cells recognize and bind to melanoma cells by a secondary "lectin-type" receptor for a carbohydrate moiety.

Identification of a structure on human melanoma cells recognized by CTL exhibiting anomalous killer cell function

The structures involved in the recognition of melanoma cells by nonspecific cytotoxic T lymphocytes (CTL) activated in mixed lymphocyte culture were investigated with monoclonal antibodies (MAb) which blocked this anomalous killer (AK) function. Of over 2000 MAb raised against melanoma cells, only three inhibited killing; one of these, an IgMk termed Leo Me13, was investigated in detail. In antibody-binding studies using a large range of cultured tumor cells, it was shown that Leo Me13 was relatively specific for melanoma cells. Of more importance, Leo Me13 inhibited conjugate formation between AK cells and melanoma target cells by 60 to 80% and caused an eight- to 10-fold reduction in killing. The MAb did not immunoprecipitate protein from melanoma cells surface-labeled with 125I, and thin-layer chromatography followed by immunoblotting of the separated glycolipids from melanoma cells indicated that the epitope was on acidic glycolipids migrating between GM1 and GD1a; moreover, treatment of melanoma cells with neuraminidase resulted in complete loss of binding of Leo Me13 but not of other anti-melanoma antibodies which did not inhibit AK cell-mediated lysis. Other melanoma-reactive MAb of the same isotype as Leo Me13 did not block killing of melanoma cells, but one documented antibody, R24, an IgG3 with specificity for the ganglioside GD3, was found to inhibit this function. These data suggest that the AK cells recognize and bind to melanoma cells by a secondary "lectin-type" receptor for a carbohydrate moiety.

Identification of a human granulocyte functional antigen (GFA-2) involved in antibody-dependent cell-mediated cytotoxicity and phagocytosis

A human neutrophil- and eosinophil-specific surface antigen, GFA-2, has been found to be involved in the antibody-dependent cell-mediated cytotoxicity (ADCC) to extracellular targets, and in phagocytosis. The monoclonal antibody (MAb) WEM-G11 was produced which recognizes the GFA-2 structure. This MAb, when used as F(ab')2, stimulated human neutrophils to kill antibody-coated P815 cells and, in the case of human eosinophils, increased their cytotoxic effect on schistosomula of Schistosoma mansoni in a dose-dependent manner. MAb WEM-G11 F(ab')2 also stimulated the phagocytosis of antibody-coated sheep erythrocytes by neutrophils. The effect of WEM-G11 F(ab')2 was specific, because other MAb, whether tested in the form of F(ab')2 fragments or as whole IgG, failed to stimulate neutrophils despite binding to these cells. In contrast to the F(ab')2 fragments of these cells. In contrast to the F(ab')2 fragments of WEM-G11, the whole IgG of this MAb inhibited ADCC and phagocytosis, presumably through interaction with granulocyte Fc receptors. WEM-G11 F(ab')2, and to a greater extent WEM-G11 IgG, induced degranulation, but only from cytochalasin B-treated neutrophils. GFA-2 was absent from lymphocytes, monocytes, erythrocytes, and myeloid and erythroid colony-forming cells, as shown by flow cytometry and colony-forming experiments. GFA-2 appeared at the promyelocytic stage and increased in density as neutrophils became more mature. In the mature neutrophil, the number of binding sites for WEM-G11 were found to be about 20,000 per cell. By immunoprecipitation, it appeared that GFA-2 consisted of a polypeptide chain of about 95,000 m.w. and a low m.w. peptide of about 43,000. By immunoblotting, it was demonstrated that the epitope recognized by WEM-G11 is in the chain of m.w. 95,000. GFA-2 thus constitutes a novel human granulocyte-specific antigen that is central to the functional activity and differentiation of these cells.

Identification of a human granulocyte functional antigen (GFA-2) involved in antibody-dependent cell-mediated cytotoxicity and phagocytosis

A human neutrophil- and eosinophil-specific surface antigen, GFA-2, has been found to be involved in the antibody-dependent cell-mediated cytotoxicity (ADCC) to extracellular targets, and in phagocytosis. The monoclonal antibody (MAb) WEM-G11 was produced which recognizes the GFA-2 structure. This MAb, when used as F(ab')2, stimulated human neutrophils to kill antibody-coated P815 cells and, in the case of human eosinophils, increased their cytotoxic effect on schistosomula of Schistosoma mansoni in a dose-dependent manner. MAb WEM-G11 F(ab')2 also stimulated the phagocytosis of antibody-coated sheep erythrocytes by neutrophils. The effect of WEM-G11 F(ab')2 was specific, because other MAb, whether tested in the form of F(ab')2 fragments or as whole IgG, failed to stimulate neutrophils despite binding to these cells. In contrast to the F(ab')2 fragments of these cells. In contrast to the F(ab')2 fragments of WEM-G11, the whole IgG of this MAb inhibited ADCC and phagocytosis, presumably through interaction with granulocyte Fc receptors. WEM-G11 F(ab')2, and to a greater extent WEM-G11 IgG, induced degranulation, but only from cytochalasin B-treated neutrophils. GFA-2 was absent from lymphocytes, monocytes, erythrocytes, and myeloid and erythroid colony-forming cells, as shown by flow cytometry and colony-forming experiments. GFA-2 appeared at the promyelocytic stage and increased in density as neutrophils became more mature. In the mature neutrophil, the number of binding sites for WEM-G11 were found to be about 20,000 per cell. By immunoprecipitation, it appeared that GFA-2 consisted of a polypeptide chain of about 95,000 m.w. and a low m.w. peptide of about 43,000. By immunoblotting, it was demonstrated that the epitope recognized by WEM-G11 is in the chain of m.w. 95,000. GFA-2 thus constitutes a novel human granulocyte-specific antigen that is central to the functional activity and differentiation of these cells.

Antibodies to the T3 antigen complex on human T cells render thymocytes unresponsive to mitogen

Human thymocytes differed from peripheral blood T cells, in that they did not proliferate in response to mouse monoclonal antibodies specific for the T3 antigen complex (UCHT1 and OKT3), even in the presence of T-cell growth factor (IL-2) or with monocytes plus IL-2. The failure to respond was not the result of inhibition by cortical thymocytes, since OKT6-negative cells also did not respond when tested under conditions of limiting dilution. Of more importance, these antibodies rendered human thymocytes unresponsive to the lectin phytohaemagglutinin when added before, during, or immediately after addition of the lectin, an effect which was much more profound than the decrease in mitogenesis caused with blood mononuclear cells. These results illustrate a clear difference between medullary thymocytes and peripheral T cells in their ability to respond to signals transduced through the T3 antigen complex.