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Y Satow

Publications and source records attributed to Y Satow.

At least 73 records · Page 4Linked to original sources
PubMed1985

Morphogenesis of human cardiac outflow.

The developmental anatomy of human cardiac outflow was studied in a series of 16 normal embryos (gestational days 29-39, crown-rump length 6-20 mm, stages 14-19). Structural features and kinetics during truncal septation (TS) were described from external photographs, serial histological sections, and computer graphic reconstructions of selected tissues. Early in the period studied, the tubular myocardium ensheathed the single cardiac lumen and spiralling conotruncal ridges, which were filled with mesenchymal cells during days 31-33. As TS began (late stage 16), the aorticopulmonary (AP) septum appeared across the dorsal wall of the aortic sac between arches IV and VI. Mesenchymal condensations formed within the AP septum, crossing the lumen bifurcation to extend along the truncal ridges to the myocardium. During days 35-37, the cephalic margin of the myocardium grew or folded in toward these mesenchymal condensations between the developing valves and within the nearby conal ridges, which appeared to fuse to separate the subvalvular outflow channels by day 39. These observations are consistent with studies in chicks and rats which suggest that mesenchymal condensations or cell death foci interact with the distal myocardial rim during TS to form a structural septation complex dividing the two arterial streams.

Aortic Valve↗
PubMed1981

Possible reduction of surface charge by a mutation in Paramecium tetraurelia.

Under voltage clamp, a mutant of Paramecium tetraurelia (teaB) shows a shift in the positive direction of the voltage sensitivity of the Ca conductance and the depolarization inactivation curve by 10 mV with no change in the total conductance. This effect can be mimicked in the wild type by the addition of external CA2+ or Mg2+. The mutation also shifts the resting potential and the voltage sensitivities of the delayed rectification (depolarization-sensitive) K conductance and the anomalous rectification (hyperpolarization-sensitive) K conductance in the positive direction to a similar extent. This systematic shift of channel voltage sensitivities is best explained by the reduction of the surface negative charges of the membrane due to the mutation.

Animals↗
PubMed1981

Mutational alteration of membrane phospholipid composition and voltage-sensitive ion channel function in paramecium.

A behavioral mutant of Paramecium tetraurelia (baA) has been isolated that has an abnormal response when placed in solutions containing Ba2+. This mutant is shown here to have a dramatic alteration of the sphingolipid and phosphonolipid composition of its ciliary membrane. This biochemical defect is present in independently isolated alleles at baA locus and segregates in crosses with the behavioral phenotype. Electrophysiologically, the mutation reduces significantly conductance of both voltage-sensitive Ca2+ channels and voltage-sensitive K+ channels. When the mutant is grown in sterol-supplemented medium, its behavior, electrophysiological properties, and lipid composition are hardly distinguishable from wild type grown under similar conditions. This mutant then, provides strong evidence that membrane lipids significantly influence the function of the membrane molecules responsible for the generation of action potentials.

Animals↗
PubMed1980

Solvent accessibility and microenvironment in a bacterial protein proteinase inhibitor SSI (Streptomyces subtilisin inhibitor).

Solvent accessibility (Lee, B. & Richards, F.M. (1971) J. Mol. Biol. 55, 379-400) was calculated for each atom of a bacterial protein proteinase inhibitor SSI (Streptomyces subtilisin inhibitor) based on crystallographic coordinates. Mainly based on this information, various chemical and spectroscopic (UV, Raman, NMR) observations made on the microenvironments of cystines, methionines, tryptophan, histidines, and tyrosines of SSI in solution were evaluated. Crystallographic data and the latter two sets of data were mainly at least qualitatively consistent with each other. These data include (1) the conformation of the two disulfide bridges, (2) the flexibility of the three methionyl side chains, (3) the extent of exposure of the indole ring of a tryptophan, (4) the environment of the two histidines, (5) the environment of the tyrosines, and (6) the hydrogen-deuterium exchangeability of peptide NH's. However, the extents of exposure of tyrosines deduced by solvent perturbation UV difference spectroscopy were significantly larger than those based on solvent accessibility calculations. Possible reasons for this discrepancy are discussed.

Bacterial Proteins↗
PubMed1980

Membrane currents of pawn mutants of the pwA group in Paramecium tetraurelia.

Membrane currents were recorded from the wild type and two pawn mutants of the pwA complementation group in Paramecium tetraurelia under a voltage clamp. Most currents are not changed by the mutations. Transient inward currents of a leaky mutant, pwA132, upon step depolarizations are less than those in the wild type. The inward transient is completely lacking in a non-leaky mutant, pwA500. The time course of the residual inward currents in the leaky mutant is not significantly different from that of wild type. The voltage sensitivity of the Ca channels in the leaky mutant is also similar to that of wild type. The inward currents upon membrane hyperpolarizations in the mutants show normal characteristics in the presence or absence of external K+. With sufficiently large, prolonged depolarization, outward currents progressively develop in the wild type but decay in the mutants. The simplest conclusion we can draw is that the pwA mutations reduce the number of functional Ca channels but do not change the channel characteristics. From the conductance measurements, 45% of the Ca channels remain in the leaky mutant pwA132, and none remain in the non-leaky mutant pwA500. By subtracting the outward currents of pwA500 from the slow and prolonged outward currents of the wild type, we have tentatively separated a Ca-induced K+ current from the voltage-dependent K+ current. The time courses of these two currents differ by two orders of magnitude.

Animals↗
PubMed1980

Ca-induced K+-outward current in Paramecium tetraurelia.

Late K-outward currents upon membrane depolarization were recorded in Paramecium tetraurelia under a voltage clamp. A Ca-induced K-outward component is demonstrated by subtracting the value of the outward current in a pawn A mutant lacking functional Ca-channels (pwA500). The Ca-induced K-outward current activates slowly, reaching a peak after 100 to 1000 ms. The current then remains steady or reaches the steady state after a decline of several seconds. EGTA2-injection experiments show that the Ca-induced K-outward current is dependent on the internal Ca2+ concentration. The current is shown to depend on the voltage-dependent Ca conductance, by study of the leaky pawn A mutant (pwA132), which has a lowered Ca conductance as well as a lowered Ca-induced K-current. The Ca-induced GK is thus indirectly dependent on the voltage. The maximal GK is about 40 nmho/cell at +7 mV in 4 mM-K+. The Ca-induced K current is sustained throughout the prolonged depolarization and the prolonged ciliary reversal.

Animals↗
PubMed1978

Internal calcium concentration and potassium permeability in Paramecium.

Ca or EGTA was ionophoretically injected into Paramecium tetraurelia to change [Ca]i. Ca decreased the resting membrane resistance and hyperpolarized the membrane. EGTA had the opposite effect. EGTA following TEA, which suppress GK, had little effect on resistance or resting potential. The I-V relation at steady state was studied before and after EGTA injection while the cell bathed in either K- or TEA-solution. The response to inward test pulses after EGTA injection was similar to that after TEA injection. These results show that [Ca]i controls a steady-state K permeability in Paramecium tetraurelia. A prolonged Ca-spike was recorded after EGTA injection. The plateau potentials in various Ca concentrations in a TEA-solution show the Nernst slope (29 mV for tenfold change in [Ca]o). This result suggests that the prolonged depolarization in this condition is due to a Ca current, after suppression of K-permeability and when [Ca]i is low. The difficulty of obtaining quantitative data on the internal Ca, and the difference between the effects of EGTA injection and TEA injection are discussed.

Calcium↗
PubMed1978

Crystal structure of a protein proteinase inhibitor, SSI (Streptomyces subtilisin inhibitor), at 4 A resolution.

The crystal structure of a protein proteinase inhibitor, SSI (Streptomyces subtilisin inhibitor), which strongly inhibits bacterial alkaline proteinases specifically, was determined at 4 A resolution using four heavy-atom derivatives. The SSI molecule can be described as an ellipsoid of about 30 X 40 X 65 A composed of two identical subunits each having dimensions of about 35 X 25 X 40 A and a molecular weight of 11,483. The subunit has an extensive beta-sheet structure, but no long alpha-helices are present. Based on the binding sites of platinum reagents known to form coordination complexes with methionine, it is speculated that the P1 residue, Met 73, of the reactive site is at the protruding edge of the subunit. At the subunit-subunit interface, a beta-sheet of one subunit is stacked on top of the corresponding beta-sheet of the other subunit.

Bacterial Proteins↗