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Biomedical subjects

J Leoni

Publications and source records attributed to J Leoni.

32 records · Page 2Linked to original sources
PubMed1984

Structural studies of sheep IgG1 precipitating and co-precipitating antibodies.

Descriptions have previously been given of the physiochemical and immunobiological behaviour of IgG co-precipitating antibodies, isolated from different animal species, compared with that of the precipitating ones belonging to the same immunoglobulin class. From those investigations it seems reasonable to assume that only one of the combining sites present in the two binding arms of the co-precipitating antibody molecule firmly binds the antigen. Consequently, the antibody does not form insoluble Ag-Ab complexes. The peptide maps, diagonal peptide maps and high voltage electrophoresis developed with peptides obtained after previous reduction and radioactive alkylation did not show differences between sheep IgG1 precipitating and co-precipitating antibodies. When diffused against rat anti-sheep IgG1 precipitating antibody serum, sheep IgG1 precipitating antibody gave a band of precipitation which was identical to the band given by sheep IgG1 co-precipitating antibody. Similar results were obtained when rat anti-sheep IgG1 co-precipitating antibody serum was used for precipitation. By immunodiffusion with cross absorbed sera no antigenic differences between the two antibodies could be demonstrated. The results obtained indicate that the different behaviour of precipitating and co-precipitating antibodies when interacting with antigen would probably not be a consequence of differences in the primary structures of their constant fragments. Both antibodies would belong to the same class, sub-class or type of immunoglobulin.

Animals↗
PubMed1984

Interaction of purified precipitating and non-precipitating (coprecipitating) antibodies with hapten and with haptenated protein. Evidence of an asymmetric antibody molecule.

The interaction of monovalent hapten dinitrophenyl epsilon-amino caproic acid (DNP-EACA) with purified IgG1 sheep anti-DNP precipitating and non-precipitating antibodies, and their F(ab')2, F(ab') and Fab fragments, was studied by fluorescence quenching and by a radioimmunoassay. The Scatchard plots of whole non-precipitating antibody and its F(ab')2 fragment showed a bi-modal curve that could be interpreted as due to the existence of two populations of sites with very different affinity for the ligand, each population representing 50% of the total number of sites. The F(ab) fragments of the non-precipitating antibody could be fractionated by immunoadsorption into two populations of high and low affinity whose association constants differed by more than 2 logs. The study of the interaction of whole antibodies with DNP-bovine serum albumin (BSA) demonstrated that each molecule of precipitating antibody can combine with two molecules of antigen but non-precipitating antibody cannot combine with more than one molecule of antigen. It is concluded that the molecule of non-precipitating antibody is asymmetric and has a site of high affinity and another of low affinity. As a consequence of this structure the non-precipitating antibody behaves functionally as univalent and is unable to form precipitates with the multivalent antigen and to activate effector mechanisms.

Aminocaproates↗
PubMed1979

[Neuromuscular block control during and after anaesthesia (author's transl)].

During many years the clinician's requirements for neuromuscular blocking drugs are satisfied by clinical investigations. Electromyographic recordings which are a satisfactory method are not useful in current practice. The use of nerve stimulators as Churchill Davidson apparatus modified for train of four impulses must reach the continental theatres, the response to neuromuscular blocking agents varying over a wide range. Five ways of stimulation can be used giving different informations, not only during anaesthesia, but so after particularly to specify the origin of some complications.

Adult↗
PubMed1977

The incomplete anti-Rh antibody agglutination mechanism of trypsinized ORh+ red cells.

The capacity for binding to trypsinized and non-trypsinized ORh+ red cells, of the IgG incomplete anti-Rh antibody and its F(ab')2 and Fc fragments has been investigated. An analysis has also been made of the capacity of non-specific human IgG, aggregated non-specific human IgG, human IgM (19S) and IgM (7S), and of fragments Fcgamma, Fcmu and Fc5mu to inhibit the agglutination of trypsinized ORh+ red cells by the IgG incomplete anti-Rh antibody. The results obtained indicate that these antibodies behave in a similar manner to that of nonprecipitating antibodies, and that the agglutination of trypsinized red cells seems to be a mixed reaction due to the interaction of an Fab fragment with its Rh antigenic determinant present in the surface of a red cell and the Fc of the same molecule with a receptor for Fc present in adjacent red cells. The trypsin treatment apparently results in the liberation of occult Fc receptors. It has also been demonstrated that in the agglutination of ORh+ red cells by IgG incomplete anti-Rh antibody in the presence of albumin, interaction must occur in some manner between the albumin and the Fc fragment since the F(ab')2 fragment does not give rise to agglutination under such conditions.

ABO Blood-Group System↗
PubMedDate not supplied

Characterization of the lipase activity of Malassezia furfur.

Enzymes capable of metabolizing lipids are essential for the growth of Malassezia furfur in vitro and in vivo. We designed a series of experiments to characterize the lipolytic system in this yeast. The optimal pH of the lipase system was 7.5 Lipase activity was detected in soluble and insoluble saline cell extracts and in supernatant from the cultures. Esterase activity screened in samples separated by native polyacrylamide gels showed that it was restricted to one band of low mobility. An FPLC analysis of the soluble saline extract demonstrated that the lipase activity was present in three major peaks with different protein composition as revealed by SDS-PAGE. The enzymatic activity and cell growth were first induced and later inhibited by increasing concentrations of polyethylene-sorbitan-monooleate (Tween-80). The characterization of the lipolytic system (e.g. its induction by substrate and the effect of pH and/or different cations) could help to explain the increment in the number of M. furfur infections related to alterations of surface lipids in the skin such as seborrheic dermatitis.

Chromatography, Liquid↗
PubMedDate not supplied

[Hereditary angioedema. Effect of danazol on C4 and functional C1INH].

Hereditary angioedema (HAE) is an inherited deficiency of the inhibitor of C1 esterase (C1 inh). Two types of genetic C1 inh deficiency have been described, type I: quantitative, and type II: functional. For the purpose of the present study, 4 out of 51 HAE patients were selected. None of them had received any previous androgenic therapy. The group was integrated by two type I and one type II cases. All patients that entered in the protocol received 400 mg/day of danazol over 14 days. The complement system was evaluated by monitoring C4, Hemolytic complement 50% (CH50), Circulating Immune Complexes (CIC), and antigenic and functional C1 INH during the study. The level of the complement factors at the beginning and the end of this period demonstrated a statistically significant increase of C4 and CH50 and the disappearance of CIC, while C1INH remained unmodified. These results suggest that the therapeutic effect of Danazol may have two mechanisms of action: i. promotion of C4 synthesis by anabolic effect resulting in an improvement of the complement system with the disappearance of CIC, and ii, a minor increase of C1 inh level primarily due to the lack of its consumption.

Adult↗
PubMedDate not supplied

Hereditary angioedema: preliminary report on skin biopsy finding of fibrin and/or C4 through immunofluorescence.

Hereditary angioedema is considered an inherited disorder of the complement system, manifested by repeated crises of angioedema involving the skin, the gastrointestinal and respiratory tracts. Biopsies of normal skin obtained from 5 patients, diagnosed with hereditary angioedema, were found to be positive for fibrin and in one case also positive for C4. The sections stained with anti-fibrin serum showed fibrin deposits around isolated epidermal cells, while C4 staining revealed a homogeneous pattern along the epidermis. Fluorescence patterns and laboratory findings before and after treatment with danazol and/or anti-fibrinolytic treatment are reported.

Adolescent↗