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Biomedical subjects

L Chedid

Publications and source records attributed to L Chedid.

At least 217 records · Page 12Linked to original sources
PubMed1971

In vitro attachment of radioactive endotoxins to lysosomes.

The experiments reported here demonstrate that under certain conditions endotoxin can interact with lysosomes in vitro. After incubation of large granular fraction with (51)Cr-labeled antigen under the conditions required for acid hydrolytic activity, radioactivity was associated with the pellet after centrifugation. This effect can be inhibited by preincubation of the large granular fraction with unlabeled homologous or heterologous endotoxins. High resolution autoradiography showed that (14)C-labeled endotoxin was predominantly attached to the lysosomes contained in the large granular fraction. The mechanism of this interaction and its relationship to the toxic effect of endotoxins on lysosomes are discussed.

Animals↗
PubMed1970

Hybridization by deoxycholate treatment or by biological degradation of bacterial endotoxins extracted from smooth and rough strains.

An endotoxin extracted with phenol-water from a rough microorganism (Salmonella typhi strain R(2)) was hybridized with an endotoxin obtained by the Boivin technique from a smooth strain (S. enteritidis Danysz) when they were mixed in the presence of sodium deoxycholate. These two toxic antigens could also be hybridized by incubation in citrated serum. With this new composite molecule, the presence of the hydrophilic side chains on the smooth moiety influenced the electrophoretic migration of the R antigen and greatly hindered the reactivity of the R sites with their specific antibodies.

Journal Article↗
PubMedDate not supplied

Stimulation of non-specific resistance to infections by synthetic immunoregulatory agents.

Muramyl dipeptide or MDP (AcMur-L-Ala-D-iGln) is a synthetic immunoadjuvant which can also enhance non-specific resistance to bacterial infections in mice, even by the oral route. By the use of several derivatives, it has been shown that neither adjuvanticity nor pyrogenicity was a perequisite for eliciting an increased resistance, and that unwanted pharmacological effects can be eliminated by minor chemical modifications. Moreover, some lipophilic analogs or derivatives obtained by linking the glycopeptide to a carrier were found to be more active than MDP. Their effectiveness also depended on the dose and the timing of administration, and varied according to the bacterial challenge. The most appropriately timed administration of MDP and derivatives was established between one and four days before the challenge. In some cases, MDP was protective even when injected one hour after the challenge, whereas with other immunostimulants such as lipopolysaccharides or BCG, a negative phase of higher susceptibility may occur under these conditions. MDP still enhanced resistance to bacterial infections in animals with a poor immune status, like newborns or adult mice under immunosuppressive treatment. Moreover, the protective activity was not impaired after repeated injections of large doses of MDP or other adjuvant analogs, a treatment which is known to inhibit specific immune responses.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

Correction of defective tumoricidal activity of macrophages from A/J mice by liposomal immunomodulators.

The ability of liposomal immunomodulators to restore abnormal macrophage tumoricidal activity has been studied. Macrophages from A/J mice have impaired responses in vitro to macrophage activating factor, gamma-interferon, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) or lipopolysaccharide when compared with macrophages from normoresponsive C57BL/6J mice. Liposomes containing a lipophilic muramyl dipeptide MDP-glyceroyl dipalmitate, macrophage activating factor or gamma-interferon restored tumoricidal activity to levels similar to C57BL/6J macrophages. Pretreatment of A/J mice with Corynebacterium parvum resulted in low levels of macrophage tumoricidal activity: treatment of C. parvum-induced A/J macrophages in vivo or in vitro with liposomal MDP-glyceroyl dipalmitate or liposomal macrophage activating factor resulted in normal levels of cytotoxicity. Macrophages from A/J mice were unable to phagocytose liposomes in vitro as rapidly or to the same extent as macrophages from C57BL/6J mice. The levels of cytotoxicity observed indicate that this is not a limiting factor for the induction of tumoricidal activity by liposomal immunomodulators.

Adjuvants, Immunologic↗
PubMedDate not supplied

Adjuvants of immunity.

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Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

Role of the proline residues on the immunogenic properties of a P. falciparum circumsporozoite peptide linked to a carrier protein.

The circumsporozoite (CS) protein of P. falciparum contains an immunodominant epitope, NADP, that is repeated 37 times in the native molecule. The presence of proline in the coat proteins of the Plasmodium parasite at various developmental stages and strains is a frequent occurrence. In this study we evaluate the influence of substitution of proline residues by glycine on the immunogenic behavior of two tandemly repeated peptides linked via glutaraldehyde to a protein carrier: The (NANP)4 P. falciparum circumsporozoite peptide and its glycine-substitute analog, (NANG)4. The results obtained show that the (NANP)4 induces antibodies which recognize the peptide free in solution, bound on a solid phase, and linked to a carrier protein. It has been previously reported that such antibodies recognize the antigenic sites of the peptide in the native protein on the surface of the sporozoite. Antibodies raised against (NANG)4 in the same experimental conditions as (NANP)4, cannot recognize the peptide free in solution or bound to the solid phase. However, these antibodies can react with the peptide when it is linked to a protein carrier. The coupling of a glycine-containing analog to a carrier results in a significant shift in its conformation, allowing it to be recognized by the antibodies.

Animals↗
PubMedDate not supplied

[Effects of mycobacterial hydrosoluble adjuvants on the induction and prevention of experimental autoimmune uveo-retinitis in guinea-pigs (author's transl)].

Experimental uveo-retinitis (EAU) was induced in guinea-pigs after one systemic injection of retinal extract mixed with the hydrosoluble adjuvants (WSA) or muramyl dipeptide (MDP). In this model, 50 micrograms of WSA in incomplete Freund's adjuvant had the same adjuvanticity as 50 micrograms mycobacteria. The MDP, tested at low doses (2 to 100 micrograms), was less effective. But MDP, even in aqueous solution without oil, stimulated the induction of a tolerance to the retinal antigen: with addition of MDP, only one injection of the antigenic preparation was sufficient to delay and clearly reduce the development of EAU induced by the antigen plus complete Freund's adjuvant two and a half months later.

Adjuvants, Immunologic↗