Yukio Matsumoto

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In this paper a purely algebraic condition for a word in a free group to be representable by a simple curve on a punctured plane will be given. As an application, an algorithm for simple closed curves on a punctured plane will be obtained. Our solution is different from any algorithm due to Reinhart [12], Zieschang [13] or Chillingworth[2]. Although the(More)
We will announce two theorems. The first theorem will classify all topo-logical types of degenerate fibers appearing in one-parameter families of Riemann surfaces, in terms of " pseudoperiodic " surface homeomorphisms. The second theorem will give a complete set of conjugacy invariants for the mapping classes of such homeomorphisms. This latter result(More)
At concentrations >50 microM, extracellular ATP dose-dependently increased cytosolic Ca2+ concentration ([Ca2+]i) via activation of P(2Z) purinoceptors in rat parotid acinar cells. This increase in [Ca2+]i is primarily due to entry of Ca2+ from the extracellular medium. Inositol trisphosphate formation and Ca2+ release from intracellular Ca2+ stores were(More)
1. Muscarinic stimulation of the smooth muscle of guinea-pig taenia caeci was produced with 10(-4) M carbachol for 15 s, 30 s, 1 min, 2 min and 30 min, and the time course of developing desensitization was studied by measuring the muscle contractility and the binding characteristics of muscarinic receptors. 2. The contractile response to carbachol was(More)
Ca2+ waves and oscillations have been observed during stimuli that generate inositol 1,4,5-trisphosphate (IP3) in several exocrine cells, including rat parotid acinar cells. Although a model has been proposed to explain the mechanism of the Ca2+ wave, there exists no direct evidence to prove the model's validity. Analysis with a permeabilized cell system(More)
The spatial characteristics of inositol 1,4,5-trisphosphate (IP3)-induced quantal Ca2+ release were examined by imaging Ca2+ concentrations within Ca2+ stores ([Ca2+]L) in permeabilized HSY cells. The image of mag-fura-2 fluorescent ratio with dual excitation (344 nm/360 nm) demonstrated that a sequential application of different concentrations of IP3 (0.1,(More)
Field and laboratory studies were conducted to examine the effects of nest availability and body size on changes in male mating tactics from sneaking to nest-holding in the dusky frillgoby Bathygobius fuscus. In the field, the body size of nest-holding males decreased from early to mid-breeding season, suggesting the possibility of a change in the tactics(More)
Androgens, for example testosterone, are major hormones that affect male courtship activity, territorial activity, sexual dimorphism, and reproductive tactics; they reach, and are maintained at, a sufficient level to express such sexual traits at the appropriate time for reproductive success. This study examined the effects of androgen levels (testosterone(More)
Sneaking tactic, a male alternative reproductive tactic involving sperm competition, is generally adopted by small individuals because of its inconspicuousness. However, large size has an advantage when competition occurs between sneakers for fertilization of eggs. Here, we suggest that both large- and small-size advantages of sneaker males are present(More)
1. We have found that development of carbachol (CCh)-induced desensitization to receptor agonists, but not to receptor by-passed stimulation, is transiently interrupted by a Ca2+-dependent resensitization during the early stage in the smooth muscle of guinea-pig taenia caeci. To further characterize the receptor-mediated signal transduction pathways(More)