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Biomedical subjects

J Hoebeke

Publications and source records attributed to J Hoebeke.

At least 163 records · Page 9Linked to original sources
PubMed1978

Equilibrium and kinetic studies of the binding of Lens culinaris lectin to rabbit erythrocytes by a quantitative fluorometric method.

The binding of Lens culinaris lectin to the receptors of rabbit erythrocytes was studied by a quantitative fluorometric method using the fluoresceinated conjugate. Equilibrium data showed the presence of 1.2 x 10(6) receptors/cell with an association constant varying from 8 to 3 x 10(6) M-1 over a temperature range of 5 to 37 degrees C. The binding reaction is exothermic with a deltaH = -4.6 kcal/mol and a deltaS = + 15 eu. It appears that most of the bound lectin molecules had only a single site occupied, the agglutination being due to a very low fraction (0.0003--0.0056) of lectin molecules with two sites occupied. The specificity of the reaction was demonstrated through its inhibition by nonfluoresceinated LL and by the specific sugars methyl alpha-D-glucoside and methyl alpha-D-mannoside. From the inhibition curves an association constant of 4 x 10(2) M-1 was calculated for methyl alpha-d-glucoside and 9 x 10(2) for methyl alpha-D-mannoside. The association and dissociation rate constants of the binding reaction are, respectively, in the range of 3--10 x 103 and 3--33 x 10(-4) M-1 s-1 in the temperature range of 5 to 37 degrees C. The activation energies of the forward and reverse reactions are 7 and 13 kcal/mol, respectively. The association constants and the binding enthalpy calculated from the activation energies were fully consistent with those obtained by equilibrium measurements.

Animals↗
PubMed1978

A quantitative fluorometric assay for detection and characterization of Fc receptors.

A new quantitative fluorometric binding assay that uses fluoresceinated aggregated IgG is proposed for the study of Fc receptors. The method was compared with a radiolabeling binding assay on three well characterized murine cell lines (38C-13, EL4, and BW). The apparent association constant of the binding and the amount of aggregated IgG bound per cell at saturation were calculated. The fluorometric assay enables the detection of 5 X 10(-10) M bound aggregated IgG. Inhibition studies with monomeric IgG, reduced and alkylated aggregated IgG, and aggregated F(ab')2 fragments of IgG confirmed the specificity of the assay. Staphylococcal protein A inhibited the binding of the aggregated IgG to Fc receptors.

Antibody Specificity↗
PubMed1976

Effects of levamisole on spontaneous rosette-forming cells in murine spleen.

Levamisole, an anti-anergic chemotherapeutic agent, is shown to depress the azathioprine sensitivity of rosette-forming cells (RFC) in the spleen of normal mice, and to restore the azathioprine sensitivity of RFC in the spleen of adult thymectomized mice. Using the fully active dose of 1.25 mg/kg i.v., the restoration effect was present 15 h after treatment with the drug and almost disappeared after 48 h. Levamisole was ineffective on RFC in vitro. These results suggest that Levamisole might interfere with the reactivity of T lymphocytes as has been described for drugs interfering with cyclic nucleotide metabolism.

Animals↗
PubMed1976

A new culture model facilitating rapid quantitative testing of mitotic spindle inhibition in mammalian cells.

A new culture model, which facilitated both mass screening of potential anticancer drugs acting on microtubules and quantitative experiments with known "antitubulins," was found to have the following advantages: use of mammalian cells (either transformed or not), simplicity of the techniques (phase-contrast microscopy or simple microscopy after Giemsa staining), and ease with which it lent itself to quantification. The model was based on the uniform multimicronucleation response induced by antitubulins in MO cells. The specificity (towards antitubulins) of this response was ascertained by the use of many substances, including most of the known antitubulins and a number of nonrelated cytostatic or cytotoxic compounds. The uniformity of the response was established with the use of time-lapse observation of large numbers of cells and quantitative approaches. The results obtained in this model with the standard antitubulins (colchicine, vinblastine, vincristine) showed similar effects. The major difference between colchicine and the Vinca alkaloids was that colchicine was less reversible, which might be an indication of stronger intracellular binding. The Vinca alkaloids acted synergistically with colchicine when threshold subactive doses were combined, although it is known that they bind at a different site on tubulins. A number of substances that have been claimed or were suspected to interfere with microtubules were tested. The results showed that the following substances were indeed active with MO cells: colchicine, vinblastine, vincristine, podophyllotoxin, rotenone, griseofulvin, mercaptoethanol, benomyl, methyl benzimidazol-2-yl carbamate, and R 17934. Compounds that were inactive on these mammalian cells in culture included isopropyl carbanilate and melatonin, both of which have been shown to be active in other systems.

Antineoplastic Agents↗
PubMed1976

Inhibition by suprofen and other non-narcotic analgesic drugs of the effects of prostaglandin precursor on isolated tissues and platelets.

Contractions caused by Slow Reacting Substance C(SRS-C) and by Arachidonic Acid hydroperoxide (AAP) in the guinea-pig ileum and by AAP in the rat fundus were studied in the presence of suprofen and of 3 reference compounds. The dose-related inhibitions were not due to antagonism of prostaglandins. Other agonists of gastrointestinal smooth muscle were not or only weakly antagonized. For the study of selective inhibition of AAP-induced contractions by non-narcotic analgesics, the rat fundus is the preferred preparation. In this model suprofen had an ED50 of 1.27 x 10(-7) M (0.033 mug/ml), being 1.5, 94 and 2, 020 times more potent than indomethacin, phenybutazone and acetylsalicylic acid, respectively. Suprofen also strongly inhibited malondialdehyde formation by guinea-pig platelets incubated with arachidonic acid. The reported effects point to inhibition by suprofen of prostaglandin biosynthesis. The antagonism of AAP-induced contractions in the rat fundus is a valuable test system for inhibitors of prostaglandin biosynthesis.

Analgesics↗