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This paper describes the chemical synthesis of a compound with voltage-gating characteristics similar to those observed in nerve membranes. For alamethicin (ALA), a natural antibiotic that induces such properties in lipid bilayer membranes, there are two proposed structures, one a cyclic and the other an open chain peptide. The open chain sequence (ALA-o) proposed by Martin and Williams [(1976) Biochem. J. 153, 181-190] was synthesized by stepwise solid-phase condensation of four fragments prepared by solid-phase synthesis. The product, purified to homogeneity, was not identical with the main component of natural ALA. Nevertheless, in lipid bilayer membranes the exponential dependence of conductance on voltage and the dependence of conductance on a high power of the peptide concentration were qualitatively similar for ALA-o and for natural ALA. Like ALA, ALA-o showed the characteristics of a channel-former, although the single-channel conductances were less well defined for the synthetic compound. This work establishes that a cyclic structure is not a necessary condition for a peptide to induce voltage-dependent conductances in membranes and that ALA-o possesses all the structural elements required for such an activity.

Chromosome analyses with banding were performed on six patients with idiopathic acquired refractory sideroblastic anemia (IARSA). One patient was found to have an extra chromosome No. 8, but had a normal level of red cell glutathione reductase. Bone marrow chromosomes from the other patients showed a normal karyotype. 28 patients with IARSA, including our 6 patients, have had chromosomal analyses. Two consistent chromosomal abnormalities have been described: a + 8 in three patients and a 20q- in three others. Despite the presence of chromosomal abnormalities in abouut one half of the patients, no patients has yet developed acute myelogenous leukemia. Several have died of hemochromatosis. The presence of a chromosomal abnormality appears to have no influence on the early course of IARSA.

Thrombin inactivation by antithrombin-III and heparin has been found to decrease in the presence of collagen, whereas thrombin activity and the rate of thrombin inactivation by antithrombin-III alone are not affected. Albumin, at the same concentration as collagen, does not influence either thrombin activity or thrombin inactivation by antithrombin-III or by antithrombin-III plus heparin.

Treatment of splenic T lymphocytes with anti-Ia antiserum inhibits the binding of antigen-antibody (AgAb) complexes to the majority (less than 50%) of Fc receptor-positive (FcR+) T cells. A similar inhibition was observed with anti-H-2D and anti-H-2K sera but not with anti-Thy 1.2. Despite the presence of Ia determinants on peripheral T cells, as established by the inhibition of AgAb binding, Ia could not be detected on peripheral T cells by immunofluorescence assays. Data obtained with the AgAb-binding inhibition assay indicate that determinants controlled by loci mapping in the I-A and I-C, S, or G regions are present on the FcR+ T cells. Evidence is presented that subpopulations of T cells within the FcR+ T-cell population may be distinguishable on the basis of which I-region-controlled determinant is expressed. The data are discussed in terms of phenotypic and functional heterogeneity of T lymphocytes.