The Sodium Channel Has Four Domains Surrounding a Central Pore

The voltage-gated sodium channel generates the action potential. This 300-kDa protein has four homologous regions, which are also homologous to the voltage-sensitive tetrameric potassium channel. We isolated sodium channels fromElectrophorus electricuselectroplax by detergent solubilization and immunoaffinity chromatography and studied their structure by electron microscopy of negatively stained specimens. Different projections were aligned, classified, and averaged. In side view, the channel protein exhibits the shape of a truncated cone, 14 nm in height. One end has a diameter of 12 nm and is asymmetric, while the other is more symmetric and has a diameter of 7–10 nm. In top views, the sodium channel appears to consist of four domains of different size and to have a stain-filled pore in the center.     

Isolation of o-(Malonylamino)benzoic Acid from Peanut Plant

A new compound was isolated from leaves of peanut. Its structure was determined as o-(malonylamino)benzoic acid on the basis of physicochemical evidences.     

Arrest reaction in man. Motor arrest response by electrical stimulation of the deep structure of the cerebrum.

In spite of many reports of arrest reaction in animals, there are very few reports in man. During a therapeutic stereotactic operation we observed peculiar phenomena caused by electrical stimulation to the deep structure of the cerebrum. This phenomenon is quite similar to that reported by Van Buren, but there are a few differences between them. Arrest reaction was observed in 14 of 23 cases, 17 of 28 tracks. Stimuli which caused the arrest reaction were 60--100 Hz square waves of 1 msec duration and 5--15 V. The electrical stimulation caused an interruption of counting and other motor actions, which could be resumed following release of stimuli. Psychic confusion or memory disturbances were not observed with the exception of a few cases. The arrest reaction that we observed is thought to be due to a direct effect on the head of the caudate nucleus, not due to secondary effects on the internal capsule and the motor fiber in vicinity of the caudate nucleus. However, the possibility that the current spread to the motor fiber cannot be definitely ruled out.     

Isolation of an inhibitor of ß-glucuronidase from porcine sublingual gland

An inhibitor of ß-glucuronidase was isolated from porcine sublingual gland by successive fractionation of trypsin extracts of the latter on Sephadex G-100, DEAE-cellulose, Sephadex G-200, and DEAE-cellulose. Its purity and homogeneity were established by DEAE-cellulose column chromatography, ultracentrifugation, and electrophoresis on cellulose-acetate membrane. The sedimentation coefficient of the purified ß-glucuronidase inhibitor was 3.75 S (S₂₀⁰, w), and the molecular weight was determined to be 340 000 from Sephadex G-200 column chromatography. The inhibitor contained 17.5% protein, 20.8% total hexoses, 19.9% hexosamine, 21.8% N-acetylneuraminic acid, and 9.6% fucose. The inhibition was non-competitive, and it was completely suppressed by the addition of NaCl, KCl, Na₂SO₄, or CaCl₂, respectively.     

Light-scattering studies of cation-stimulated filament assembly of newborn rat epidermal keratin

Effects of CaCl2 on in vitro polymerization of keratin extracted from cornified cells of newborn rat were investigated by means of light-scattering and supramolecular structures. Elongation and parallel assembly of filaments occurred with addition of CaCl2 to dialyzed keratin solutions and was detected by an increase in light-scattering intensity. Nonfibrous aggregates which occurred in higher buffer concentrations and in lower pH were also recorded as intensity increased. MgCl2, ZnCl2, and GdCl3 demonstrated similar effects, but NaCl and KCl showed no effect.     

Target-selective cytotoxicity of methotrexate conjugated with monoclonal anti-MM46 antibody

Summary In studies on antitumor antibody-cytotoxic drug conjugates as potential tumor-selective cytotoxic agents, methotrexate (MTX) was conjugated via its active ester derivative with a murine monoclonal antibody (aMM46) to a mouse mammary tumor antigen (MM antigen) on syngeneic, ascitic C3H/He mouse mammary tumor MM46 cells. The conjugate retained full antibody activity, as assayed by complement-dependent cytolysis. The target-selective cytotoxicity of aMM46-MTX was verified by the observations that this conjugate showed greater cytotoxicity than the corresponding normal mouse immunoglobulin (nIg) conjugate to MM46 cells, neither aMM46 nor nIg being cytotoxic, and that it showed less cytotoxicity to MM antigen negative mouse mammary tumor MM48 cells than to MM46 cells, its cytotoxicity to MM48 cells being similar to that of the nIg conjugate. From the results of assays of cell binding and uptake of ¹³¹I-labeled aMM46 and aMM46-³H-MTX, aMM46 and aMM46-MTX were internalized after their binding to MM46 cell surface antigen. Leupeptin, an inhibitor of the lysosomal endopeptidase cathepsin, decreased the cytotoxicity of aMM46-MTX, supporting the involvement of lysosomal degradation of the conjugate in its action.