Browsing by Author "Van Regenmortel, M H V"

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    Immunochemical studies with tryptic peptides of tobacco mosaic virus protein
    (1979) Milton, Raymond Cecil de Lisle; Van Regenmortel, M H V
    The antigenic determinants of the protein subunit of tobacco mosaic virus CTMV) have been studied by inhibition of complement fixation, inhibition of micro-precipitin and direct binding experiments. The viral subunit has been found to possess six antigenic determinants. Two of these, situated in tryptic peptide I (residues 1-41), were found to be a cryptotope (i.e. an antigenic determinant absent from the outer surface of the assembled viral capsid) and a viral antigenic determinant. Tryptic peptides 4 (residues 62-68) and 8(residues 93-112) also contained cryptotopes which were situated in the region of residues 63-65 and 108-112 respectively. Tryptic peptide 12 (residues 142-158) contained both a cryptotope and a neotope (i.e. an antigenic determinant which is only expressed on the outer surface of the viral capsid), which are situated in the C-terminal region of the polypeptide chain of the TMV protein, residue156 being associated with the cryptotope and residue 158 with the neotope. No antigenic activity could be demonstrated in tryptic peptide I I (residues 135-141 ). When the results are analyzed in terms of the three-dimensional structure of the viral subunit, it appears that all the antigenic reactive regions occupy highly accessible locations on the surface of the protein.
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    A proposed role for the Ca ion in the chemotactic response of Physarum polycephalum
    (1977) Ludlow, Christopher Trimble; Van Regenmortel, M H V
    Durham, in a review published in 1974, presented the following hypotheses concerning the factors that control amoeboid movement: (1) actin and myosin are present in all cells that exhibit amoeboid movement and, changes in the internal [Ca⁺⁺] regulate contraction, (2) filaments of actin and myosin form an intimate association with the surface membrane and depending on the local [Ca⁺⁺] , the filaments can cause the membrane to relax or become rigid, (3) Ca⁺⁺ fluxes across the external membrane (viz. efflux and influx) regulate the state of contraction in the proposed actinomyosin-surface membrane network and, (4) such Ca++ fluxes operating across the membrane manifest themselves (especially with slime mould plasmodia) as waves of adhesion running across the undersurface of a cell and aid in movement. A working hypothesis, that encompasses the ideas of Durham, is that Ca⁺⁺ entry and efflux across the external membrane control such cellular processes as extension of pseudopodia, exocytosis, endocytosis and the direction of movement (chemotactic response) of amoeboid cells. In the specific case of slime mould plasmodia, which best exemplify all of Durham's hypotheses, the simplest hypothesis to explain the control of chemotaxis is that attractants (sugars, food; organisms) cause a Ca⁺⁺ efflux across the membrane and a subsequent movement forward. Repellents would act in a reverse manner by causing Ca⁺⁺ entry. This hypothesis also allows for the existence of a Ca⁺⁺-accumulating organelle. This organelle might replace or act in concert with the proposed Ca⁺⁺ fluxes across the external membrane. The investigations reported in this thesis were devised to examine experimentally this hypothesis.
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    Study of macroglobulinaemia in Trypanosoma equiperdum infections of the rabbit
    (1976) Ross, J M; Van Regenmortel, M H V
    1. 195 IgM, 75 IgM, and IgG were purified from the serum of Trypanosoma eguiperdum infected rabbits. The following antisera were also prepared for the quantitation of rabbit IgM and IgG: i. goat anti rabbit IgM antiserum; ii. goat anti rabbit IgG antiserum; iii. goat antiserum to rabbit serum proteins. 2. The serum levels of 195 IgM, measured by gel diffusion and rocket immunoelectrophoresis were shown to increase approximately ten times at the peak of the Trypanosoma eguiperdum infections in the rabbit. The serum IgG. concentrations, measured by gel diffusion increased more than seven times.aver the infection period. Low molecular weight 75 IgM was also detected in the serum by rocket immunoelectraphoresis and quantitative gel diffusion, but accurate concentration determinations could not be made. 3. Rheumatoid factors were not detected by passive haemagglutination and latex fixation tests, despite the use of a variety of sensitizing globulins. These results failed to confirm earlier reports of the presence of rheumatoid factors in infected rabbits. 4. After separation of the 75 and 195 fractions by density gradient centrifugation, both fractions were found by complement fixation to contain anti trypanosome antibodies. These antibodies were also detected by immunofluorescence in the serum and 75 fractions, and by agglutination in the 195 fractions. 5. The 195 fractions also contained complement fixing antibodies reacting with the tissue antigens of rabbit liver, heart and kidney. Maximum titres of 1/80 - 1 /160 were found at the peak of the infection. Absorption of the rabbit sera with trypanosomes indicated that the trypanosomal and tissue antibodies were distinct.