Biomedical subjects

M Nachman

Publications and source records attributed to M Nachman.

5 recordsLinked to original sources

PubMed1992

Membrane-based receptor affinity chromatography.

Membrane-based receptor affinity chromatography (MRAC), which utilizes the molecular recognition between an immobilized receptor and its soluble protein ligand, has been developed for the purification of human interleukin-2 and related biomolecules. The multi-purpose affinity membrane used in this study consisted of a soluble form of interleukin-2 receptor (IL-2R) chemically bonded to hollow-fiber membranes in an oriented fashion. A model system involving anti-Tac-H (a humanized monoclonal antibody to IL-2R) was used to study the important factors influencing the performance of MRAC, including support morphology, mass transfer rate and adsorption kinetics. All three are shown to be highly efficient. MRAC has been successfully applied to the purification of anti-Tac-H, recombinant human interleukin-2 (rIL-2) and interleukin 2-Pseudomonas exotoxin fusion protein (IL2-PE40). Overall, MRAC was found to be a viable, scalable and extremely productive affinity purification method.

Adsorption↗

PubMed1992

Kinetic aspects of membrane-based immunoaffinity chromatography.

With a view towards the efficient large-scale purification of recombinant proteins, factors influencing antigen-antibody adsorption kinetics were studied in a model hollow-fiber membrane-based immunosorbent. Non-diffusion-controlled, homogeneous adsorption kinetics are approached in membranes. It is shown that adsorption kinetics, rather than mass transfer, first becomes limiting in membrane-based immunoaffinity chromatography (MIC). Antigen adsorption is not kinetically limited, even at low feed-stream antigen concentrations. Binding efficients approach theoretical values when antibody coupling densities are decreased sufficiently. Antigen breakthrough during adsorption occurs near the membrane's observed binding capacity. The results of these kinetic studies were essential in the development of highly efficient and productive MIC systems for the purification of three recombinantly produced biotherapeutics, interferon-alpha 2a, interleukin-2 and interleukin-2 receptor.

Adsorption↗

PubMed1991

Localization in human interleukin 2 of the binding site to the alpha chain (p55) of the interleukin 2 receptor.

Human interleukin 2 (IL-2) analogs with defined amino acid substitutions were used to identify specific residues that interact with the 55-kDa subunit (p55) or alpha chain of the human IL-2 receptor. Analog proteins containing specific substitutions for Lys-35, Arg-38, Phe-42, or Lys-43 were inactive in competitive binding assays for p55. All of these analogs retained substantial competitive binding to the intermediate-affinity p70 subunit (beta chain) of the receptor complex. The analogs varied in ability to interact with the high-affinity p55/p70 receptor. Despite the lack of binding to p55, all analogs exhibited significant biological activity, as assayed on the murine CTLL cell line. The dissociation constants of Arg-38 and Phe-42 analogs for p70 were consistent with intermediate-affinity binding; the Kd values were not significantly affected by the presence of p55 in binding to the high-affinity IL-2 receptor complex. These results confirm the importance of the B alpha-helix in IL-2 as the locus for p55-receptor binding and support a revised model of IL-2-IL-2 receptor interaction.

Amino Acid Sequence↗

PubMed1990

Story recall under monaural and binaural conditions. Patients with anterior temporal lesions.

Recall of a short story is ordinarily the same whether it is heard in the left, right, or both ears. It has been reported that many patients with severe cerebral dysfunctions (including brain damage, major psychiatric disorders, and learning disabilities in children) perform much better with one ear than the other (monaural asymmetry) and that binaural performance is worse than with the better ear alone (binaural interference). Blocking the poorer ear with an earplug is said to significantly improve speech comprehension in daily life. Because of the theoretical and practical significance of these reports, we have attempted a replication. We studied patients with anterior temporal lobectomy because it was proposed that the underlying mechanism of monaural asymmetry and binaural interference in all clinical categories may involve temporal lesions or abnormal inhibition of one temporal lobe by the other. We were unable to confirm the previous reports.

Adolescent↗

PubMed1975

Role of illness in producing learned taste aversions in rats: a comparison of several rodenticides.

Several toxic agents were compared in order to test the effect of various types of illness in producing learned taste aversions. After a 10-min sucrose drinking trial, groups of rats were injected intraperitoneally with lithium chloride or with a strong, near lethal dose of a rodenticide. Strong sucrose aversions were acquired by groups injected with lithium chloride, copper sulfate, sodium fluoroacetate, or red squill, and very weak or no aversions were learned by groups injected with thallium, warfarin cyanide, or strychnine. The results were discussed in terms of onset of symptoms, duration of symptoms, and kinds of physiological effects necessary to produce aversions. It was concluded that the effects of different drugs may be mediated by different physiological systems learned taste aversions.

Animals↗