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Biomedical subjects

A Takeuchi

Publications and source records attributed to A Takeuchi.

At least 559 records · Page 31Linked to original sources
PubMed1972

Location and description of spiral-shaped microorganisms in the normal rat cecum.

Some indigenous microorganisms have been shown to localize in certain anatomical sites of the digestive tract of mammals. We studied the ceca of normal adult rats by light and electron microscopy to determine whether any specific bacterial population localizes in this area. All rats studied showed that the crypt was packed with organisms whose morphological character differs from those of the cecal lumen. Organisms localized in the crypt were often identified topographically close to the microvilli of the epithelial cells. These organisms could be differentiated into three types according to their characteristic ultrastructure. Type 1 was a thin spiral-shaped microbe that resembled a Borrelia. Type 2 possessed helically coiled fibers and flagella-like appendages. Type 3 was spiral-shaped but lacked axial fibers. Types 1 and 2 were both capable of penetrating through the crypt epithelium into the lamina propria where they were found in either phagocytes or extracellular locations. These observations are discussed in relation to other host-microflora localization patterns.

Animals↗
PubMed1972

Ultrastructural identification of spirochetes and flagellated microbes at the brush border of the large intestinal epithelium of the rhesus monkey.

Spiral-shaped organisms exclusively and intimately populate the brush border of the cecal and colonic epithelium of healthy monkeys (Macaca mulatta). These organisms replace the glycocalyx, destroy most microvilli, and attenuate the terminal web of the brush border. Despite these remarkable alterations, the remaining host cellular structure is unchanged. Two structurally distinct microbes, a spirochete and a flagellate, were recognized by electron microscopy. These spirochetes share the general characteristics of other known spirochetes: they are 3 to 6 mum long and 0.2 to 0.4 mum wide, spiral 2 to 6 times, and have axial fibrils of 6-12-6 and 4-8-4 arrangements. Flagellated microbes are 4 to 6 mum long and 0.2 to 0.4 mum wide, spiral 2 to 4 times, and are characterized by a polar flagellum which originates from the terminal button at each end of the cytoplasmic body. This in vivo ultrastructural study of anaerobic spiral-shaped organisms bypasses the difficulties of in vitro culture techniques and provides a detailed description and identification of these organisms in their host environment.

Animals↗
PubMed1971

Anion interaction at the inhibitory post-synaptic membrane of the crayfish neuromuscular junction.

1. The membrane potential and the membrane conductance of the crayfish muscle fibre in solutions containing various anions were measured with intracellular micro-electrodes.2. When Cl(-) in the solution was replaced by Br(-), NO(3) (-), I(-) or CNS(-), the addition of gamma-amino butyric acid (GABA) produced a transient hyperpolarization of the membrane.3. The reversal potential of the inhibitory junctional potentials (i.j.p.s) was at a slightly depolarized level relative to the resting potential in the normal Cl(-) solution. When Cl(-) in the bathing solution was replaced by foreign anions, the reversal potential shifted towards the hyperpolarized level. The hyperpolarization was in the order CNS(-) > I(-) > NO(3) (-) > Br(-).4. When a part of Cl(-) in the bathing solution was substituted by Br(-), the inhibitory membrane conductance activated by GABA was increased as the concentration of Br(-) increased. The inhibitory membrane conductance decreased when one quarter or a half of Cl(-) was replaced by CNS(-), NO(3) (-) or I(-), but it increased again in higher concentrations of these anions.5. Ca(2+), Mg(2+) and Ba(2+) showed no appreciable effect on the inhibitory membrane conductance activated by GABA, while they decreased the conductance of the resting muscle membrane.6. It was suggested that, at the activated inhibitory membrane, there is an interaction between anions and the permeability of Cl(-) is decreased by the presence of foreign anions, such as CNS(-), I(-) and NO(3) (-). The present results support the idea that the activated inhibitory membrane is charged positively and anions penetrate the membrane interacting with the charge sites.

Aminobutyrates↗
PubMed1971

Variations in the permeability properties of the inhibitory post-synaptic membrane of the crayfish neuromuscular junction when activated by different concentrations of GABA.

1. The membrane conductance of the crayfish muscle was measured with intracellular micro-electrodes. Increase in the membrane conductance induced by various concentrations of gamma-amino butyric acid (GABA) was measured in the Br(-), NO(3) (-), I(-) and CNS(-) solutions and compared with that in Cl(-) solution. When the membrane was activated by lower concentrations of GABA, the resulting membrane conductance in NO(3) (-) and I(-) solutions was larger than in Cl(-) solution, while the membrane conductance activated by higher concentrations in NO(3) (-) and I(-) solutions were smaller than in Cl(-) solution. The membrane conductance activated by GABA was larger in Br(-) solution and smaller in CNS(-) solution than the membrane conductance activated in Cl(-) solution, throughout the concentration range of GABA examined.2. The reversal potential of inhibitory junctional potentials (i.j.p.s) was measured shortly after replacing Cl(-) by foreign anions: Br(-), NO(3) (-), I(-) and CNS(-). In I(-) solution the i.j.p.s produced by lower stimulation frequencies showed a reversal potential at a more hyperpolarized level than those produced by higher stimulation rates.3. Shortly after replacing Cl(-) by I(-), the GABA potential induced by iontophoretic application showed a triphasic potential change at the ;reversal' potential. The reversal level of the GABA potential produced by smaller doses was at a more hyperpolarized level than that produced by larger doses.4. Possibilities of a concentration effect of GABA are discussed. It is suggested that the relative permeability of the crayfish inhibitory membrane to anions changes depending on the concentration of GABA.

Aminobutyrates↗