Applicability of Macroscopic Wear and Friction Laws on the Atomic Length Scale.

Using molecular dynamics, we simulate the abrasion process of an atomically rough Fe surface with multiple hard abrasive particles. By quantifying the nanoscopic wear depth in a time-resolved fashion, we show that Barwell's macroscopic wear law can be applied at the atomic scale. We find that in this multiasperity contact system, the Bowden-Tabor term, which describes the friction force as a function of the real nanoscopic contact area, can predict the kinetic friction even when wear is involved. From this the Derjaguin-Amontons-Coulomb friction law can be recovered, since we observe a linear dependence of the contact area on the applied load in accordance with Greenwood-Williamson contact mechanics.

Experimental study of resistance to infection by Trichophyton mentagrophytes: demonstration of memory skin cells.

The mechanisms governing the development of local immunity in experimental dermatophytosis were studied by injecting intravenously trichophytin in guinea pigs cured of a prior Trichophyton mentagrophytes infestation. Dermal cell modifications were observed which were greater in the healed zones than in those not affected during the prior dermatophyte inoculation. These modifications included lymphocyte activation and accumulation and an accumulation of basophilic leukocytes. These observations suggest that after an acute dermatophyte infection heals, immunocompetent cells remain which are more numerous at the sites of lesions and that these cells would be responsible for the increased rate of elimination of the fungus during a reinfection. This hypothesis is discussed in the framework of the relationships observed in dermatophyte infections between delayed type hypersensitivity and resistance.

Localization, biosynthesis, processing and isolation of a major 126 kDa antigen of the parasitophorous vacuole of Plasmodium falciparum.

Monoclonal antibodies prepared against a 50 kDa antigen found in Plasmodium falciparum culture supernatants identify a 126 kDa polypeptide which can be localized by immunofluorescence and immunoelectronmicroscopy at the periphery of the schizonts. This polypeptide is released from the infected erythrocytes by mild saponin lysis and is probably a component of the parasitophorous vacuole. Pulse chase kinetic analysis demonstrated its disappearance from the parasitized red blood cell from 6 to 10 h after being synthesized and the concomitant appearance of the 50 kDa molecule in the culture supernatant. Purification of metabolically labeled, schizont infected cells demonstrated that spontaneous release of merozoites is needed for the processing of the 126 to the 50 kDa whereas reinvasion is not. Polyclonal antibodies were raised in rabbit against affinity purified 126 kDa protein. These antibodies, together with another 126 kDa specific monoclonal antibody have enabled us to characterize two other cleavage products of the 126 kDa antigen in culture supernatants, namely 47 and 18 kDa polypeptides. We believe that the processing of the 126 kDa protein into low molecular weight fragments reflects a proteolytic event which may participate in merozoite release.

A 50 kilodalton exoantigen specific to the merozoite release-reinvasion stage of Plasmodium falciparum.

The immunoglobulins G of a human plasma inhibiting in vitro Plasmodium falciparum merozoite reinvasion have been purified and used to immunoprecipitate the antigens released into the culture medium by an [35S]methionine-labeled synchronous culture. Several of the major exoantigens identified were found throughout the entire life cycle; they were also immunoprecipitated from the labeled parasitized cells. Some antigens were found only after the reinvasion stage, and especially a major one of molecular mass 50 kDa and pI 5.5. The latter was not found in the parasitized cells but derived most likely from the processing of a major 126 kDa antigen which disappeared from the parasites during the reinvasion period and which was immunoprecipitated by an anti-50 kDa monoclonal antibody.

Characterization of a 225 kilodalton rhoptry protein of Plasmodium falciparum.

A monoclonal antibody (24C6 4F12) raised against Plasmodium falciparum culture supernatant antigens gave a multiple dot picture on schizonts when assayed by immunofluorescence on P. falciparum erythrocytic stages. The corresponding antigen was localized in the peduncle of rhoptries by immunoelectronmicroscopy. On Western blots of P. falciparum schizonts, a major antigen of 225 kDa and a minor one of 240 kDa were recognized by this McAb. Pulse chase analysis of [35S]methionine biosynthetic labeling of P. falciparum culture demonstrated that the 240 kDa molecule was the precursor of the 225 kDa and that its processing occurred between 0 and 4 h after synthesis. Biosynthesis of the 240-225 kDa antigen occurred only during schizogony.

Serotypic antigens of Plasmodium falciparum recognized by serotype-restricted inhibitory human sera.

Immune sera from some Cambodian refugees contain functional serotypic antibodies that inhibit invasion of erythrocytes by the Camp strain but not by the FCR-3 strain of Plasmodium falciparum. Using a new assay, the "competitive heterologous antigen assay" (CHAA), the serotypic antibodies in a pool of three inhibitory sera were characterized by the antigens they precipitated. In the CHAA, immunoprecipitation of antigens by antibodies to common or cross-reacting antigenic determinants was blocked with excess heterologous unlabeled FCR-3 antigens before 3H-labeled Camp schizont and merozoite antigens were immunoprecipitated. The predominant Camp strain serotypic antigens revealed after electrophoresis and autoradiography were the major 195 Kd glycoprotein surface antigen (gp195) and its processed products at 150, 83, 73, and possibly 45 Kd. Additional serotypic antigens were identified at 180, 130, 65, 50, and 32 Kd. It is likely that one or more of these serotypic antigens is a target for the serotypic antibodies that inhibit invasion.

Immunochemical analysis of a major antigen of Plasmodium falciparum (P126) among ten geographic isolates.

Protein P126, a parasitophorous vacuole major antigen of Plasmodium falciparum and precursor of 3 major exoantigens (50, 47, and 18 Kd in strain FCR-3) has been studied in 10 culture-adapted isolates originating from various endemic areas. Two monoclonal antibodies (specific for 50 and 47 Kd exoantigens, respectively) were used to immunoprecipitate culture supernatants and parasitized erythrocytes in each case. It was observed that all the parasite isolates reacted with both monoclonal antibodies, indicating the ubiquity of the epitopes analyzed. Further, two of the exoantigens (the 50 and 18 Kd of FCR-3) were found to have a stable molecular mass in all the isolates tested, whereas, the other one (47 Kd in FCR-3) was found to have a variable molecular mass, from 47 to 50 Kd. The molecular mass of the precursor varied from 126 Kd to 128 Kd. No correlation was found between geographic origin and antigenic size.

Plasmodium falciparum strain-specific human antibody inhibits merozoite invasion of erythrocytes.

The extent to which human antibodies involved in functional immunity react with antigenic determinants varying between different isolates or strains of the human malaria parasite Plasmodium falciparum will influence the design of vaccines against malaria. We identified nine immune sera from Cambodian refugees which blocked in vitro invasion of erythrocytes by merozoites of the Camp strain of P. falciparum and agglutinated Camp strain merozoites. However, none of these sera blocked invasion of erythrocytes by merozoites of the FCR-3 strain. We conclude that antibodies in these human sera recognized antigenic determinants present on the surface of viable merozoites of the Camp strain but not the FCR-3 strain. These parasite strains and in vitro assays can be used to analyze strain-specific functional immunity in humans.

Parasitologic and immunologic studies of experimental Plasmodium falciparum infection in nonsplenectomized chimpanzees (Pan troglodytes).

Parasitologic, hematologic, and immunologic parameters were monitored in intact (nonsplenectomized), adult chimpanzees infected with a "chimp-adapted" strain of Plasmodium falciparum. Following primary and secondary injections of 10(9) P. falciparum-infected erythrocytes, each chimpanzee developed a low grade parasitemia (up to 1,000/mm3) and maintained the infection without evidence of eliminating the parasites. Hematologic and serum biochemical values, as well as the majority of immunologic parameters tested, remained unaltered in infected chimpanzees. However, 2 weeks after infection T cells from infected chimpanzees demonstrated an enhanced response in vitro to stimulation with the mitogen PHA, and monocyte phagocytic activity for antibody-coated erythrocytes (Fc-mediated phagocytosis) increased significantly. During malarial infection, apes developed a strong T cell proliferative response to P. falciparum antigens and monocytes showed enhanced phagocytic activity for P. falciparum-infected erythrocytes in the absence of immune serum. These results suggest that cellular immune mechanisms, especially macrophage activation, may help control, but not eliminate, P. falciparum malaria in chimpanzees.

Decreased growth of Plasmodium falciparum in red cells containing haemoglobin E, a role for oxidative stress, and a sero-epidemiological correlation.

The in vitro growth of Plasmodium falciparum in red cells containing haemoglobin E (HbE) was studied at oxygen concentration of 5 to 20%, with and without antioxidants. Under all conditions, parasite growth decreased as the concentration of HbE increased as compared with growth in red cells containing only HbA. The decreases were proportionately greatest at the highest oxygen concentration. The antioxidant vitamin C partially reversed the decreases in growth observed in HbE-containing cells at 20% oxygen. South-east Asian refugees with HbAE or HbEE had high antimalarial IFA titres, indicative of exposure to malaria more frequently than did refugees with HbAA. The decreased growth of P. falciparum in HbE-containing red cells may reduce the severity of malaria infections, conferring a survival advantage and thus increasing the numbers of individuals with HbE in local areas of South-east Asia with high incidences of malaria.

[Human anisakiasis: 5 cases in northern France]. / Anisakiase humaine: 5 cas dans le nord de la France.

We report 5 cases of human anisakiasis revealed respectively by an acute intestinal obstruction due to multiple small bowel stenosis, an acute inflammatory ileitis simulating appendicitis, ulcer type epigastralgia, purulent peritonitis and a latent small bowel tumor. Diagnosis was established in 4 cases on microscopic analysis of bowel specimens (eosinophilic granulomas and/or parasitic fragments) and in 1 case at gastroscopy. Serodiagnosis was positive in 2 of 4 cases and the consumption undercooked fishes was found in 4. In small samples we estimated the infestation (1 to 50 parasites) by anisakis larvae of 3 fish species: 80 p. 100 for herrings, 63 p. 100 for mackerels and 100 p. 100 for whitings. This work emphasizes the role of anisakiasis as a source of digestive symptoms and intestinal eosinophilic granuloma.

[Current role of amphotericin B in the treatment of deep mycoses]. / Place actuelle de l'amphotéricine B dans le traitement des mycoses profondes.

Amphotericin B (Am. B), a polyene heptaene, is an antifungal antibiotic substance produced by Streptomyces nodosus, a telluric actinomycetal from Venezuela. Although it is a very toxic substance and its pharmacokinetic is not completely known, Am. B is yet the former antifungal substance utilised against number of pathogenic agents of systemic mycoses. Am. B binds irreversibly to sterols of fungal cytoplasmic membranes causing a leak of potassium and other impairments leading the fungal cell to death. Further, Am. B might to induce an enhancement of humoral and cellular immunity. After intravenous perfusion, 95 per cent of Am. B binds to plasma lipoproteins. Only a low proportion of the Am. B serum level is detected in the CSF. Distribution of Am. B to extravascular inflammatory fluids and secretions might be letter. Am. B might be eliminated essentially by biliary way. Am. B toxic effects are very frequent. Generalized reactions are observed to the earlier doses. Toxic visceral, above all, nephrotoxic manifestations, appearing later. Recent results, from experimental and human infections suggest that Am. B encapsulated in liposomal vesicles is more active, less toxic and more easily administered.

[Application of a co-electrosyneresis reaction to the diagnosis and serological surveillance of candidiasis in a hospital milieu]. / Applications d'une réaction de co-électrosynérèse au diagnostic et à la surveillance sérologique des candidoses en milieu hospitalier.

We have previously described a co-immunofiltration reaction which identifies a specific precipitating system (SPCS) in sera from patients presenting systemic candidiasis. The SPCS is characterized by coalescence with an experimental serum directed against the germinative tubes of Candida albicans. The present study concerns our experience of the use of co-immunofiltration in routine hospital practice. Complete observations involving clinical, mycological and serologic data were selected in order to illustrate various possible developmental trends for SPCS during candidiasis. The SPCS usually develops early infections due to the yeast species most frequently implicated in hospital pathologies; an increase in its intensity reflects a developing infection or the start of therapy. The SPCS disappears slowly and gradually when infectious development is favorable, but its sudden disappearance represents an unfavorable prognosis correlated with detection of circulating antigens. Circulating antigens are also seen in severe cases of candidiasis in which the SPCS is not present. Indeed there is a certain complementarity between these two observations.

[Parasitologic study of feces: simultaneous performance of Faust's, Janecko-Urbanyi's and Ritchie's concentration technics]. / Examen parasitologique de selles: réalisation simultanée des techniques de concentration de Faust, de Janeckso-Urbanyi et de Ritchie.

The authors propose the simultaneous use of Faust's, Janeckso-Urbanyi's and Ritchie's techniques according to a protocol which combines the effectiveness of the three techniques, with a saving in reagents, a significant simplification of the manipulations (a single dilution of the stools, a single straining and a total of three centrifugations) and the possibility of conducting valid comparative studies, as the three techniques are performed from the same faecal aqueous suspension.

[Fungal infections: involved species and minimal inhibitory concentrations of common antifungal agents]. / Infections à levures: espèces concernées et concentrations minimales inhibitrices des antifongiques usuels.

Fungal cultures of cutaneous or ungual origin (477 cultures), nasopharyngeal and urogenital origin (2,000 cultures), and blood, internal organs, surgical incisions, and catheters (300 cultures) were obtained in this study. Analysis of the data yielded the following information: Candida albicans and C. tropicalis, frequent causes of superficial or systemic mycoses, were very sensitive to flucytosine and amphotericin B in a liquid medium, but less sensitive to the imidazole derivatives; C. parapsilosis, a cause of superficial and systemic mycoses, was remarkably sensitive to all four antifungal agents tested; Torulopsis glabrata and C. krusei are of greatest concern in a hospital setting since systemic or visceral infections are minimally sensitive to antifungal agents; C. pseudotropicalis, C. guilliermondii, and C. zeylanoides are less pathogenic and sensitive to antifungal agents varies, depending on the strain. Specific measures are presented for management of fungal infections in a hospital setting. The role of antifungal susceptibility testing in everyday practice is also evaluated.

[Vulvar granuloma due to Enterobius vermicularis (author's transl)]. / Granulome vulvaire oxyurosique.

The authors report a case of casual discovery of a enterobiasic vulvar granuloma arising on the left labia. This woman, living in Lille (France), 70 years had been treated by surgery and roentgentherapy for a well differentiated squamous carcinoma of the vulva. They consider the question of the genital localisation of Enterobius vermicularis in women and discuss the pathogenic hypothesis.

Molecular dynamics simulations of mixed lubrication with smooth particle post-processing.

A post-processing method for molecular dynamics (MD) simulations of friction based on the smooth particle approach is proposed, allowing--among other features--the introduction and evaluation of a solid-solid contact area arising due to direct asperity interaction. In order to illustrate the feasibility of this scheme, a large number of MD calculations of lubricated nanotribological systems with various asperity geometries and carefully selected numbers of lubricant molecules were carried out and analysed. In this manner, it is shown that the friction force as a function of load agrees very well with a three-parameter friction law which, in addition to the adhesion- and the load-controlled terms, contains a load-independent offset.