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Biomedical subjects

K Sakabe

Publications and source records attributed to K Sakabe.

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

Progestin receptors in adult rat ovary during estrous cycle.

Using a synthetic progestin (P)(i.e. R5020), characteristics of P receptors were determined in the ovarian tissue cytosols from adult estradiol benzoate-treated or 4-day cycling rats. In the estradiol benzoate-treated rats a specific 3H-R5020 binding in the cytosol was found with a number of binding sites, V max = 110 fmol/mg protein and the equilibrium dissociation constant, Kd = 14 nM. In the 4-day cycling rats, specific binding was found in the 6-7 S region with the Vmax which fluctuated during the estrous cycle: the sequence of Vmax (fmol/mg protein) was 395 (proestrus) greater than 122 (diestrus) greater than 96 (late estrus) greater than 62 (metestrus) greater than 40 (early estrus). The Kd value varied during the cycle, the highest (22 nM) in proestrus and the lowest (5 nM) in early estrus. In addition, 3H-R5020 binders were thermolabile and of protein in nature. These results suggest that the rat ovary contains P receptors in its cytoplasm with high affinity and low capacity of P binding, the level of which fluctuates during the estrous cycle.

Animals↗
PubMed1984

Oscillation of electrical potential in a porous-membrane doped with triolein induced by an Na+/K+ concentration gradient.

The electrical potential across a fine pore membrane doped with trioleoyl glyceride (triolein) and separating aqueous solutions of 0.5M NaCl and 0.5M KCl, respectively, was studied. It was found that this system showed rhythmic and sustained oscillations of electrical potential between the two aqueous solutions. These oscillations were attributed to the change of permeability of Na+ and K+ ions across the membrane, which originated from the phase-transition of triolein molecules within the fine pores.

Mathematics↗
PubMed1984

Oscillation of electrical potential in a porous membrane doped with glycerol alpha-monooleate induced by an Na+/K+ concentration gradient.

The electrical potential across a fine-pore membrane doped with glycerol alpha-monooleate and separating aqueous solutions of 0.5 M NaCl and 0.5 M KCl was studied. It was found that this system showed rhythmic and sustained oscillations of electrical potential. These oscillations may be due to the phase transition of glycerol alpha-monooleate molecules within the fine pores. In relation to this, it is shown here that Na+ and K+ have different effects on the aggregation of glycerol alpha-monooleate. This oscillatory phenomenon is very interesting because in biological nervous membrane an Na+/K+ concentration difference across the membrane is essential for excitability.

Glycerides↗
PubMed1984

X-ray diffraction photographs of chicken gizzard G-actin.DNase I complex crystals taken with synchrotron radiation.

X-ray diffraction photographs of a chicken gizzard G-actin.DNase I complex crystal have been recorded using the synchrotron radiation beam emitted by the Synchrotron Radiation Source at Daresbury and the Photon Factory at Tsukuba. The resolution limit was extended to 2.4 A and the exposure time was reduced approximately by a factor of 10, when data recorded at the Photon Factory, were compared with those recorded with a conventional rotating-anode source. Using a newly designed Weissenberg camera equipped with a multi-layer line screen, the diffraction data in a 36 degrees oscillation range were recorded on a single film up to 3.5 A resolution.

Actins↗
PubMed1984

Autoradiographic study on localization of progestin target cells in the chicken testes.

Using an autoradiographic technique, the localization and concentration of progestin (P) in cell constituents of testes from the immature 25-to-70-day-old and mature 120-day-old chickens were investigated. After incubation of the frozen tissue sections with 3H-Promegestone (R5020), a synthetic P, specific radioactivity, was found in the seminiferous epithelium and interstitium in all the animals in the presence or in the absence of various non-radioactive steroids, and the intensity of radioactivity differed with age: high in 25-, 70-and 120-day-old chickens, and low in 50-day-old chickens. Estrogen treatment enhanced the intensity of radioactivity in the cells at all ages. The concentration of radioactivity was higher in the seminiferous epithelium than in the interstitial cells. In the frozen tissue sections, it was not possible to identify the kind of cell taking up the high amount of radioactivity. These results indicate that the testes from chicken during their growing stages contain cell constituents that specifically bind P.

Age Factors↗
PubMed1983

Crystallographic studies of the chicken gizzard G-actin X DNase I complex at 5A resolution.

The structure of the chicken gizzard G-actin X DNase I complex has been determined at 5 A resolution by an X-ray diffraction method. Protein phases were computed by the multiple isomorphous replacement method using four heavy atom derivatives. The mean figure of merit was 0.65. Dimensions of the three molecular species, the complex, G-actin and DNase I, were determined based on the "cypress wood" models derived from the electron density map. The natures of the heavy atom binding sites are discussed in relation to the distinction between the two component molecules. The pattern of successive contacts between actin molecules observed in the present crystal seems unrelated to that found in F-actin.

Actins↗
PubMed1983

Estrogen receptor in the "non-lymphocytes" in the thymus of the ovariectomized rat.

Estrogen binding components have been characterized in cytosols from lymphocyte fractions and non-lymphocyte fractions of the thymus and mesenteric lymph node of ovariectomized rats. The cytosol from the non-lymphocyte fraction of the thymus contained high affinity-specific binding estrogen receptor (equilibrium dissociation constant .=. 3 X 10(-10) M, number of binding sites .=. 10 fmol/mg protein) with a sedimentation coefficient of 8 S. The receptor showed specific binding for estradiol-17 beta, estrone and estriol, but not for corticosterone, progesterone or testosterone. Only lower estrogen binding was observed in the cytosols from the lymphocyte fraction of both tissues and the non-lymphocyte fraction of the lymph node. Morphological changes of the thymus in ovariectomized rats after administration of estradiol benzoate were also observed. Clustered vacuoles with incomplete microvilli in the epithelial cells increased in number and in size after estrogen treatment. These findings suggest that the effect of estrogen on the thymus is mediated via the cytoplasmic estrogen receptor in the non-lymphocytes, probably thymic epithelial cells.

Animals↗
PubMed1983

Effect of ovarian steroids on uptake of radioactive amino acids by brain tissues.

Effects of two major ovarian hormones, estrogen (E) and progesterone (P), on the uptake of amino acids by the brain nuclei of ovariectomized mice were examined. They were divided into four groups: (1) oil controls, (2) P-treated, (3) estradiol benzoate (E2B)-treated, and (4) E2B-primed P-treated mice. Two hr after the last hormonal treatment they were given a single s.c. injection of a mixture of 3H-leucine and 3H-methionine, and then sacrificed 2 hr later. Intensity of the uptake of radioactivity was measured on autoradiograms of the stained tissue sections. Group 1 showed a relatively high uptake of radioactivity by the SO, PV and SPH, compared with that by the remaining brain cells. Group 2 had a slight enhancement of the uptake by the VM, SPH and CC, compared with that in group 1. Group 3 showed a significant enhancement of the uptake by most of the preoptico-hypothalamic nuclei except for the VM, DM and PM, compared with that in group 1. Group 4 had slightly enhanced uptake by the POM, POL, SCH, SO, PV, VM, ARC, SPH and CC, compared with that in group 1. E-priming affected the uptake; it enhanced the uptake by the VM and SPH, and inhibited it by the PVA, AH, LH and CC. Uptake by the PM and EC remained unchanged in all groups. The present results suggest that two major steroids, E and P, influence protein synthesis in most of the brain regions including the preoptic and hypothalamic areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1983

Progestin receptors in ovaries of 4-day cycling rats. An autoradiographic study.

Using an autoradiographic technique we investigated in vitro the localization of cell constituents with concentrations of a radioactive synthetic progestin (P), 3H-R5020 (17 alpha, 21-dimethyl-19-nor-pregna-4, 9-diene-3, 20-dione) and its metabolites in the ovaries of 4-day cycling adult rats. After incubation of the ovarian tissue sections with radioactive R5020 in the presence or absence of various non-radioactive steroids, specific labeling was found in the tissue sections in each phase of the estrous cycle. The intensity of labeling in the ovary during the estrous cycle was highest in proestrus, followed by that in diestrus, metestrus and estrus. The intensity of labeling in cell constituents was as follows: granulosa cells greater than luteal cells greater than thecal cells greater than stromal cells. These results indicate that the rat ovaries contain cell constituents that specifically bind P and that the intensity of binding fluctuates during the estrous cycle.

Affinity Labels↗
PubMed1979

Crystallization and preliminary crystallographic data of chicken gizzard G-actin . DNase I complex and Physarum G-actin . DNase I complex.

Smooth muscle G-actin from chicken gizzard and Physarum plasmodium G-actin both interact with DNase I and form 1 : 1 complexes. These complexes were crystallized by using polyethylene glycol 6000 as a precipitant. Both crystals belong to the same orthorhombic space group P2(1)2(1)2(1). The cell dimensions of chicken gizzard G-actin.DNase I complex are a=42.00 +/- 0.07 A, b=225.3 +/- 0.4 A, and c=77.4 +/- 0.1 A, while those of Physarum G-actin.DNase I complex are a=42 A, b=221 A, and c=77 A.

Actins↗
PubMedDate not supplied

Estrogenic xenobiotics affect the intracellular activation signal in mitogen-induced human peripheral blood lymphocytes: immunotoxicological impact.

The present study was an attempt to elucidate the effect of estrogenic xenobiotics on the proliferation of mitogen-stimulated human peripheral blood lymphocyte (PBL). Our findings follow: (a) the proliferation of PBL in response to phytohemagglutinin (PHA) was mediated by protein kinase C activity, but estrogenic xenobiotics had a strong inhibitory effect on protein kinase C activity of PHA-stimulated PBL; (b) cytoplasmic extracts from PHA-stimulated PBL greatly activated DNA replication, but estrogenic xenobiotics had a strong inhibitory effect on these activities. The results suggest that the cytoplasmic signal-generating system in mitogen-treated PBL is inhibited by estrogenic xenobiotics, and that the defect occurs at all stages in the sequence of events leading to DNA synthesis and cell proliferation.

Adult↗