Biomedical subjects
K Oikawa
Publications and source records attributed to K Oikawa.
Studies on the riboflavin-binding capacity of the rat lens.
Previous studies have confirmed that riboflavin-binding protein exists in the rat lens. We now provide evidence that riboflavin-binding was the same at 4 degrees C and 37 degrees C, that there was a saturation curve when 14C-riboflavin was the substrate, that there was an ATP-dependent increase of binding, and that EGTA and PCMB did not affect riboflavin binding while it was decreased upon protease digestion and upon the addition of heavy metal compounds. Furthermore, binding was lower in the lenses of rats which had been fed a B2-deficient diet for 8 weeks than in animals receiving this diet for 4 weeks. When 14C-B2 butyrate rather than 14C-riboflavin was the substrate, binding was considerably higher in the lens homogenate and the single whole lens. Partial purification of riboflavin-binding protein using flavinyl agar-bead affinity chromatography confirmed the presence of a trace amount of riboflavin-binding protein in the bovine lens. Our results suggest that changes in the riboflavin-binding capacity of the lens may play a role in the regulation of absorption, transport and metabolism of riboflavin in the lens associated with the synthesis of ester forms of riboflavin.
Purification and characterization of troponin C from pike muscle: a comparative spectroscopic study with rabbit skeletal muscle troponin C.
The conformation of troponin C (TN-C) isolated from the white muscle of pike (Esox lucius), in the Ca2+ and metal-free states, was studied by circular dichroism, absorption difference spectroscopy, solvent perturbation difference spectroscopy, intrinsic fluorescence, thiol titration, and 1H nuclear magnetic resonance spectroscopy. In addition, the molecular weight of the protein was determined by sedimentation equilibrium and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The composition of the protein was established by amino acid analysis. The resulting data were compared with those from the widely studied analogue isolated from rabbit skeletal muscle. The results indicate near equivalence in many of the properties of pike and rabbit TN-C, such as molecular weight, the magnitude of the calcium-induced conformational change, and urea- or thermal-induced denaturability. However, the pike protein has five additional potential carboxyl groups, and there is good evidence from NMR, solvent perturbation, and fluorescence studies for the presence of a buried tyrosine residue in the apo state.
[Difference in motility between anterior and posterior gastric wall after anterior and/or posterior truncal vagotomy].
The present experiment was designed to see the effect of anterior or posterior truncal vagotomy on the movement of anterior and posterior walls of the stomach with the use of electromyography and force transducer. A total of 28 dogs were prepared with strain gages and bipolar electrodes at both anterior and posterior walls of the stomach. Three types of vagotomy, namely, anterior, posterior and bilateral truncal vagotomy were carried out consecutively or independently. Postoperatively, myoelectrical and contractile activities were compared between the anterior and the posterior wall of the stomach at fasted and fed state. Results are summarized as follows: 1) Motor activity of the control dogs could be divided into digestive, intermediate and interdigestive patterns. 2) Following 3 types of vagotomy, an appearance of the interdigestive pattern showed a tendency of delay which was more evident after the posterior than after the anterior truncal vagotomy. 3) There was little difference in contractile force of the antrum before and after 3 types of vagotomy, except that the hunger contraction was found weaker after all the 3 types of vagotomy. Vagotomy showed little effect on the frequency of basic electrical rhythm at any conditions. 4) In any observation mentioned above, there was no significant difference in the gastric motility between the anterior and posterior wall of the stomach. In conclusion, the patterns of motor activity were more affected after the posterior than after the anterior truncal vagotomy. Little difference in gastric motility, however, was found between the anterior and posterior wall of the stomach after all the 3 types of vagotomy.
The effect of terbium on the structure of actin and myosin subfragment 1 as measured by circular dichroism.
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Studies on the delayed neurotoxicity of organophosphorus compounds- (I).
Delayed neurotoxicity experiments of an organophosphorus compound, TOCP, on hens and quails were carried out. The animals were orally exposed with TOCP in dose of 400 mg/kg, and maintained for 25 and 50 days under observation, respectively. They were sacrificed and dissected at different periods after the exposure, and the histopathological examinations were made on those animals. During the periods of 50 days, no abnormal symptoms except for acute poisoning were noted in the quails. As to the hens, neurological disorders were observed from around 12 days of the experiment. In hens, the morphological alteration in the earlier stage of the experiment was perivascular cuffing of small round cells seen in the cerebrum, cerebellum and spinal cord. The major alteration was degeneration of axons and myelin in the white matter of the spinal cord. A minimal degree of these changes was found even in the hens in which the clinical signs of neurotoxicity had not yet been observed. Later the process expanded to the whole spinal cord as well as the sciatic nerve. The electron microscopy performed after 15 days revealed moderate change of myelin and axons. From these results, it was concluded that the clinical signs as well as the morphological changes were closely related to the exposure of the compound, TOCP.
[Nursing process/nursing of schizophrenic patients. Evaluation of the nursing process. Discussion].
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Intravascular coagulation in mice by the compact-colony-forming active substance (CCFAS) extracted from a strain of Staphylococcus aureus.
The compact-colony-forming active substance (CCFAS) extracted from a Staphylococcus aureus strain was capable of killing mice only when Staph. aureus, Staph. epidermidis or Escherichia coli was injected i.v. before the injection of CCFAS. In the mice killed 30 min after treatment with heat-killed Staph. aureus and CCFAS, remarkable congestion of the lung and thrombus-like lesions in the kidney were observed. In the mice killed 6 h after injection with CCFAS and living Staph. aureus congestion and inflammatory-cell filtration were found in the liver, especially within the Glisson's capsule. However, when mice were killed 30 days after treatment with CCFAS and Staph. aureus, fibrin and hyalin thrombi were observed most frequently in the renal glomeruli but also in the liver and lung.
[Fundamental studies of thyro-SHure kit (TSH) (author's transl)].
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The effects of terbium and lanthanum on the biological activity of some representative muscle protein systems.
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[Clinical evaluation of cystine aminopeptidase (CAP) (author's transl)].
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Circular dichroism studies of native and chemically modified Ca2+-dependent protein modulator.
The structural features of the native Ca2+-dependent protein modulator and two chemically modified derivatives, namely, nitrotyrosyl modulator and alkylated modulator, were examined by circular dichroism. The binding of Ca2+ to the native molecule was accompanied by an increase in helical content from 40 to 49%, with little effect on the local environments of aromatic residues in the modulator. The Mg2+ and Mn2+ do not elicit the conformational change induced by the binding of Ca2+, which also stabilizes the modulator against urea denaturation. The overall secondary structure of nitrotyrosyl modulator is indistinguishable from that of the native protein and undergoes a similar conformational change upon binding Ca2+. These observations are in agreement with the fact that nitration has no effect on modulator functions. Furthermore, nitrotyrosyl modulator interacts with troponin I only in the presence of Ca2+, as detected by circular dichroism (cd). On the other hand, alkylation of five methionine residues on the modulator with benzyl bromide affects protein conformation, as evidenced by a reduced helical content of only 35%. Alkylated modulator retains the ability of the native protein to bind Ca2+ although the affinity of this derivative for Ca2+ is reduced some three orders of magnitude relative to the native protein, with Kd = 3.2 X 10(-4) M. The results with the alkylated modulator, in conjunction with previous cd studies on N-chlorosuccinimide oxidized modulator are utilized to advance a model for the Ca2+ activation of modulator protein, based on three conformational states of the molecule.
A scanning electron microscopic study on the liver of mice.
The three-dimensional fine structures of several tissue components of the liver in normal mice were studied by scanning electron microscopy. The tissue components observed were as follows: hepatocytes, sinusoidal endothelial cells, the Kupffer cells, fat-storing cells, reticulin fibers and epithelial cells of the bile duct. Two types of fenestrations were found in the sinusoidal endothelial cells. One was smaller and clustered, and the other larger and scattered. Both of them were distributed equally throughout the hepatic lobule. Intercellular gaps were found at the endothelial junction. The Kupffer cell which was localized in a large gap between the endothelial cells was characterized by numerous villous projections, and by the absence of fenestrations which were observed in the endothelial cells. Fat-storing cells were located between hepatocytes. They elongated their processes into the space of Disse, but never protruded into the sinusoidal lumen. They were clearly distinguished from the endothelial cells and the Kupffer cells by their morphological feature and location. No transitional form was seen among the endothelial cells, the Kupffer cells, and the fat-storing cells.
A scanning electron microscopic study on hepatic changes induced by mouse hepatitis virus-2.
No significant changes in the structure of the liver were seen until 9 hr after the inoculation of mouse hepatitis virus-2 (MHV-2) into mice. At the 24 hr stage, distinct swelling of hepatocytes and narrowing of sinusoidal lumina were observed from the middle to the central area of the hepatic lobules. Most of the Kupffer cells were swollen. Their villous projections were decreased in number, and the remaining projections became like blebs. Virus particles appeared from this stage in the hepatocytes, the Kupffer cells and the space of Disse. At the 48 hr stage, parenchymal necrotic foci were present in the central and the middle area of the lobules. The necrotic change was increased from 72 hr after inoculation, and was followed by submassive or massive necrosis. It is suggested that hepatic necrosis in both the central and the middle area, or in either area, of the lobules was advanced by aggravation of the sinusoidal microcirculation, as a result of the swelling of the hepatocytes and the Kupffer cells in addition to the direct affection by virus. Fine granulation was observed on the surface of most of the central flagella of the bile duct. Some flagella were degenerated, and came in part to be a fibrillar net.
[Development of gated cardiac imaging using gamma imager (author's transl)].
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Laband syndrome: report of case.
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[Evaluation of double antibody radioimmunoassay for alpha-fetoprotein (author's transl)].
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Circular dichroism studies on Ca2+-dependent protein modulator oxidized with N-chlorosuccinimide.
The structural features and Ca2+-binding properties of native and N-chlorosuccinimide-oxidized modulator protein were compared by circular dichroism. In the presence of Ca2+,the far-UV spectra of native and oxidized modulator protein are virtually indistinguishable, indicating that oxidation of surface methionine residues does not alter the overall conformation of the molecule. In the absence of Ca2+, however, the circular dichroism spectra of native and oxidized modulator are different with calculated helical contents of 40% and 26%, respectively. As judged by circular dichroism titration studies, the native modulator contains both high-(Kd = 1.9 X 10(-7) M) and low-affinity (Kd = 4 X 10(-4) M) Ca2+-binding sites, whereas the modified modulator appears to possess only low-affinity sites (Kd = 3.8 X 10(-4) M). The reduced secondary structure in Ca2+-free oxidized modulator protein may account for the absence of high affinity Ca2+ binding sites.