Search PubMed⌕ Search

Biomedical subjects

T Hamanaka

Publications and source records attributed to T Hamanaka.

At least 55 records · Page 3Linked to original sources
PubMed1993

[Reliability and validity of the Japanese version of the coping inventory for stressful situations (CISS): a contribution to the cross-cultural studies of coping].

OBJECTIVE: There has recently been a dramatic increase in the number of studies on coping behavior as an intervening variable between stress and health. Most of the available measures of coping are, however, psychometrically inadequate. We therefore decided to develop the Japanese version of the Coping Inventory for Stressful Situations (CISS) with special regards to its cross-cultural equivalence, reliability and validity. The CISS is a self-report measure of an individual's typical pattern of coping along three orthogonal dimensions of Task-, Emotion-, and Avoidance-oriented coping; its reliability and validity have been well studied in North America, where it was originally developed. METHOD: We obtained the Japanese version of the CISS (J-CISS) by means of back-translation. In Study 1, we administered the J-CISS and the 12-item General Health Questionnaire (GHQ) to 33 Japanese university students twice with an interval of four weeks. In Study 2,550 Japanese high school students completed the J-CISS and the Maudsley Personality Inventory. RESULTS: The equivalence of the Japanese version with the original was ascertained by means of back-translation involving multiple, independent mental health professionals and by factor congruence between the two versions. A principal component factor analysis (Varimax rotation) of the Study 2 data allowed us to extract three factors, which were virtually identical to the original ones. The high corrected item-remainder correlations, internal consistency reliabilities and test-retest reliabilities all attested to the reliability of the J-CISS. In order to examine its content validity, we compared the J-CISS with two coping questionnaires that have been in use in Japan, and found that the J-CISS covered most of the coping styles in these two questionnaires. However, such coping styles as "giving up," "to lose is to win (a Japanese proverb)," "it is best to do nothing" were not included in the original CISS and hence in the J-CISS. The criterion validity of the J-CISS was examined both in terms of predictive validity and concurrent validity. In Study 1, those who scored below the cut-off of the GHQ at Time 1 but above the cut-off at Time 2 had significantly higher Emotion-oriented coping scores at Time 1 than those who remained below the cut-off of the GHQ at Times 1 and 2 (predictive validity). In Study 2, the J-CISS scales and the MPI scales showed theoretically predicted correlations (concurrent validity). The results of the factor analysis and the corrected item-remainder correlations were suggestive of high construct validity of the J-CISS. Moreover, the mean inter-item correlation was between .20 and .40 for each scale, indicating its homogeneity. Factor analysis of each scale revealed that each scale indeed contained only one factor. Correlations among the three scales of the J-CISS established that the three scales formed multi-dimensional measures of coping. CONCLUSION: The results of our study indicate 1) that the obtained Japanese version of the CISS is to be regarded as final, 2) that coping styles can be measured in a consistent and reliable manner both in Japan and North America, and 3) that this cross-cultural equivalence as well as the other validity studies have further augmented the validity of the CISS itself.

Adaptation, Psychological↗
PubMed1992

Small-angle synchrotron x-ray scattering reveals distinct shape changes of the myosin head during hydrolysis of ATP.

In the energy transduction of muscle contraction, it is important to know the nature and extent of conformational changes of the head portion of the myosin molecules. In the presence of magnesium adenosine triphosphate (MgATP), fairly large conformational changes of the myosin head [subfragment-1 (S1)] in solution were observed by small-angle x-ray scattering with the use of synchrotron radiation as an intense and stable x-ray source. The presence of MgATP reduced the radius of gyration of the molecule by about 3 angstrom units and the maximum chord length by about 10 angstroms, showing that the shape of S1 becomes more compact or round during hydrolysis of MgATP. Comparison with various nucleotide-bound S1 complexes that correspond to the known intermediate states during ATP hydrolysis indicates that the shape of S1 in a key intermediate state, S1-bound adenosine diphosphate (ADP) and phosphate [S1**.ADP.P(i)], differs significantly from the shape in the other intermediate states of the S1 adenosine triphosphatase cycle as well as that of nucleotide-free S1.

Adenosine Triphosphate↗
PubMed1992

Aspects of the development of Schlemm's canal.

We have tried to answer the question of whether the endothelium of Schlemm's canal is derived from and retains properties of blood vessels by studying: (1) the development of Schlemm's canal in human fetal eyes; (2) the existence of Weibel-Palade bodies in human neonatal, adult human and adult monkey eyes; and (3) the presence of blood coagulation Factor VIII-related antigen in adult human and monkey eyes. (1) We observed that the intrascleral plexus of the limbal region extended deep into the sclera forming a deep scleral plexus by the 17th week of gestation. After 17 weeks gestation, extensions from the deep scleral plexus had reached the region of the future corneoscleral meshwork where the trabecular cells appeared oriented circumferentially. The blind endings of these extensions appeared to grow circumferentially in the supposed region of Schlemm's canal and at 27 weeks gestation they formed an incomplete Schlemm's canal. A complete Schlemm's canal was observed in some sections of the limbal region at 28 weeks gestation and at approximately 40 weeks gestation the canal was complete in most sections. (2) Weibel-Palade bodies were found in the endothelium of aqueous veins and in the inner and outer wall endothelium of Schlemm's canal. (3) Blood coagulation Factor VIII-related antigen was detected in the endothelium of the collector channels and Schlemm's canal, as well as in the blood vessels of the other parts of the eye. Our results indicate that the endothelium of Schlemm's canal is derived from a vascular origin and that even in the adult eye it retains some of the properties of a blood vessel.

Adult↗
PubMed1992

Inhibition of tryptophan hydroxylase by (R)- and (S)-1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinolines (salsolinols).

The (R)- and (S)-enantiomers of salsolinol, the dopamine-derived tetrahydroisoquinolines, were found to inhibit the activity of tryptophan hydroxylase (TPH), prepared from serotonin-producing murine mastocytoma P-815 cells. Inhibition of TPH by salsolinols was found to be non-competitive with the substrate L-tryptophan. Tryptophan hydroxylase is composed of two elements with different kinetic properties in terms of cofactor (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin and these two elements were inhibited by salsolinols in competitive and uncompetitive ways, respectively. Stereoselectivity of salsolinol was not observed, concerning the potency and the type of inhibition on PTH. These data indicate that salsolinols might be naturally occurring inhibitors of indoleamine metabolism.

Animals↗
PubMed1992

The absorbance spectrum and photosensitivity of a new synthetic "visual pigment" based on 4-hydroxyretinal.

The firefly squid, Watasenia scintillans, is the only animal known to possess a visual pigment in which the chromophore is 4-hydroxyretinal. This paper describes the absorbance spectrum and some properties of a synthetic "A4" visual pigment generated from bovine opsin and 4-hydroxyretinal. The absorbance spectrum of this pigment is compared with (a) bovine rhodopsin and (b) a rhodopsin template with the same lambda max as the synthetic visual pigment. The A4 pigment is shown to have an absorbance spectrum that is almost identical to that of a rhodopsin template. It is also shown that the photosensitivity and thermal stability of the A4 pigment, dispersed in detergent micelles, is essentially similar to that of rhodopsin.

Animals↗
PubMed1992

The vasculature and clinical application of the posterior tibial perforator-based flap.

Use of the posterior tibial flap pedicled on the posterior tibial vessels has been described by several authors, but with it there is the major disadvantage of an unavoidable transection of the posterior tibial artery. To overcome this disadvantage, we anatomically studied the perforators from the posterior tibial artery and used posterior tibial perforator-based flaps clinically. Based on our anatomic study of 25 cadaveric legs, the cutaneous perforators were considered to be distributed from the distal to the proximal sides of the lower leg through the medial border of the tibia, and they were classified into three types: septocutaneous perforators mainly located in the distal third of the leg, muscle perforators located in the proximal half, and periosteal perforators in the proximal third of the leg. The average size and number of perforators was 0.8 mm and 3.1 in one leg, respectively. A considerable number were located at sites from 70 to 140 mm superior to the medial malleolus. Based on our clinical cases repaired with flaps, we consider this flap to be useful as a free flap for the repair of defects of the extremities and as an island flap for reconstruction of defects on the anteromedial aspect of the lower leg. The territory of the flap is relatively wide, being 19 x 13 cm. The long saphenous vein can be used safely as the venous drainage system in the case of free-flap transfer.

Adult↗
PubMed1991

Conformation changes of cuttlefish (Euprymna morsei) rhodopsin following photoconversion.

Cuttlefish (Euprymna morsei) rhodopsin solubilized in lauryl ester of sucrose and its photoproduct, acid metarhodopsin, were examined by small-angle X-ray scattering and chromatofocusing to investigate the conformation changes of visual pigment following photoconversion. From spectroscopic studies, it was found that more than 93% of Euprymna rhodopsin could be converted to meta form under the condition of red light irradiation at neutral pH. Since almost pure acid metarhodopsin solution was prepared without changing the specimen concentration, the small-angle X-ray scattering intensities of both pigment-detergent complexes were directly compared. The radius of gyration increased on going from rhodopsin to acid metarhodopsin by approximately 1.5%. There were also discernible changes in the secondary peak intensities. The distribution function, derived by the Fourier transformation of intensity data, showed a significant change around 55 A. The maximum linear dimension of the rhodopsin-detergent complex was about 95 A and hardly changed after illumination. Intensity at zero angle did not change after illumination, suggesting that the aggregation did not occur. The change of the intensity profile could be due to the conformational change of the pigment-detergent monomers. The pI value of rhodopsin determined by chromatofocusing was 5.32 and that of acid metarhodopsin was 5.06, indicating that a few carboxyl groups are newly dissociated. The shift of the protein mass and the charge redistribution were observed following photoconversion.

Animals↗
PubMed1991

Time-resolved synchrotron X-ray diffraction studies of a single frog skeletal muscle fiber. Time courses of intensity changes of the equatorial reflections and intracellular Ca2+ transients.

Time-resolved X-ray equatorial diffraction studies on a single frog skeletal muscle fiber were performed with a 10 ms time resolution using synchrotron radiation in order to compare the time courses of the molecular changes of contractile proteins and the intracellular Ca2+ transient during an isometric twitch contraction at 2.7 degrees C. Measurements of the Ca2+ transient using aequorin as an intracellular Ca2+ indicator were conducted separately just before and after the X-ray experiments under very similar experimental conditions. The results, which showed a similar time course of tension to that observed in the X-ray experiment, were compared with the aequorin light signal, tension and the intensity changes of the 1,0 and 1,1 equatorial reflections. No appreciable change in both reflection spacings indicated that the effect of internal shortening of the muscle was minimized during contraction. The intensity change of the equatorial reflections generally occurred after the aequorin light signal. In the rising phase, the time course of increase in the 1,1 intensity paralleled that of the rise of the light signal and the intensity peak occurred 20-30 ms after the peak of the light signal. The decrease in the 1,0 intensity showed a time course similar to that of tension and the intensity minimum roughly coincided with the tension peak, coming at 80-90 ms and about 60 ms after the peaks of the light signal and the 1,1 intensity change, respectively. In the relaxation phase, the 1,1 intensity seemed to fall rapidly just before the tension peak and then returned to the original level in parallel with the decay of tension. The 1,0 intensity returned more slowly than the tension relaxation. Thus, the change of the 1,1 intensity was faster than that of the 1,0 intensity in both the rising and relaxation phases. When the measured aequorin light signal was corrected for the kinetic delay of the aequorin reaction with a first-order rate constant of either 50 or 17 s-1, the peak of the corrected light signal preceded that of the measured one by approx. 30 ms. Thus, the peak of the Ca2+ transient appeared earlier than the peaks of the 1,1 and 1,0 intensity changes by 50-60 and 110-120 ms, respectively. The time lag between the extent of structural change and the Ca2+ transient is discussed in relation to the double-headed attachment of a cross-bridge to actin.

Aequorin↗
PubMed1991

Effects of volatile anesthetics on bacteriorhodopsin in purple membrane, Halobacterium halobium cells and reconstituted vesicles.

In this study, we have investigated effects of volatile anesthetics on absorption spectra, proton pumping activity and decay of photointermediate M of bacteriorhodopsin (bR) in differently aggregated states. Anesthetics used in this study are ether-type general anesthetics; enflurane and sevoflurane. The observed effects on bR depend not only on variety or concentration of anesthetics but also strongly on the aggregation state of bR molecules in the membrane. In purple membrane (PM), bR having maximum light absorption at 567 nm (bR567) is formed in the presence of sevoflurane or a small amount of enflurane, while a species absorbing maximally at 480 nm (bR480) is formed upon the addition of large amounts of enflurane. X-ray diffraction studies show that the former species maintains crystallinity of PM, but the latter does not. In reconstituted vesicles where bR molecules exist as monomer, even sevoflurane forms bR480. Flash photolysis experiments show that bR567 contains a shorter-lived M intermediate absorbing maximally at 412 nm in the photoreaction cycle than bR does and that bR480 contains at least two long-lived M intermediates which seem to absorb maximally near and at lower than 380 nm. The measurements of light-induced pH changes of the whole cells and of the reconstituted vesicles in the presence of the anesthetics indicate that bR567 has a enhanced proton pumping efficiency, while bR480 has a quite low or no activity. No significant difference was observed in the anesthetic action between two inversely pumping vesicles. These observations suggest that on the formation of bR480, anesthetics enter into the membrane and affect the protein-lipid interaction.

Anesthetics↗
PubMed1990

Inhibition of human brain aromatic L-amino acid decarboxylase by cooked food-derived 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and other heterocyclic amines.

A carcinogenic, food-derived heterocyclic amine, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), was found to inhibit aromatic L-amino acid decarboxylase isolated from human brainstem. Trp-P-2 inhibited the enzyme activity toward L-DOPA more markedly than that toward 5-hydroxytryptophan. The inhibition was competitive to a cofactor of the enzyme, pyridoxal-5-phosphate, and the Ki value of Trp-P-2 was 163 microM. The enzyme activity could be fully recovered after removal of Trp-P-2 by gel filtration, which indicates that the inhibition was reversible. Among a series of heterocyclic amines examined for their effects on the activity toward L-DOPA, Trp-P-2 was the most potent inhibitor, followed by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, then Trp-P-1. Another heterocyclic amine, 2-amino-3-methyl-9H-pyrido[2,3-b]indole also inhibited the enzyme. The inhibition of the decarboxylase activity by these heterocyclic amines may affect the catecholamine metabolism in human brain.

5-Hydroxytryptophan↗
PubMed1990

X-ray diffraction and flash photolysis studies of M intermediate of lattice-contracted purple membrane.

The effects of cross-linking and lattice contraction of purple membrane (PM) on the photodynamics of bacteriorhodopsin (bR) and on the tertiary structure were studied by flash photolysis and X-ray diffraction. To get a contracted lattice form of PM, native PM, and/or PM cross-linked by glutaraldehyde were treated with deoxycholate or Triton X-100. Part of the Triton-treated cross-linked PM was further incubated with Bio-Beads SM-2 to remove Triton X-100. In the modified PM, several long-lived components of the M intermediate appeared, the features of which were related to the environment of bR. Also, X-ray diffraction studies using synchrotron radiation were performed on the modified PM under intense light irradiation (lambda greater than 500 nm) in which 40-80% of bR was photoconverted to the M state. In the Triton-treated cross-linked PM dispersed in 0.25% Triton X-100, the unit cell of membrane crystalline lattice was enlarged from 58.8 to 59.8 A and the crystalline order decreased with irradiation. The analysis of X-ray diffraction patterns suggests that light-induced conformational changes of bR correlated with the Triton content of the environment and an increase of substitution disorder was caused by these changes, but the average location of bR was unchanged. However, the other modified PM showed no significant changes of diffraction, upon light irradiation.

Absorption↗
PubMed1990

[A case of necrotizing scleritis with angiitis of papilla].

A case of a 66-year-old woman suffering from polymyalgia rheumatica with necrotizing scleritis followed central retinal artery occlusion in the left eye was studied clinico-pathologically. The left eye was enucleated because of severe pain in spite of the steroid therapy, and was examined histopathologically. The necrotic granulomatous changes of the deep sclera in the ciliary body and peripheral fundus were observed. Lymphocytes, plasma cells and epitheloid cells infiltrated in the central retinal artery at the papilla. It seemed that subconjunctival injection of steroid had induced scleral necrosis. When scleritis is very severe, it might be suggested that systemic steroid should be given in large suppressive doses.

Female↗
PubMed1989

[Aspects of aqueous humor drainage through Schlemm's canal].

The structure and function of the outflow routes via Schlemm's Canal are discussed. Recent measurements of the pressure in the intertrabecular space, Schlemm's canal, and the episcleral veins in monkeys indicate that most of the resistance is located between the anterior chamber and Schlemm's canal. Platelets may play a role in Schlemm's canal by occluding artificial breaks and pores which are large enough to permit contact between platelets and the subendothelial tissue. The invaginations of the endothelial cells of the inner wall of Schlemm's canal are likely to prevent such contact if the pores in their wall towards the canal are small.

Animals↗
PubMed1989

Scleral spur and ciliary muscle in man and monkey.

The development of the human scleral spur and the role of the scleral spur in human and monkey eyes were studied by measuring the height of the scleral spur, the thickness of the uveal meshwork and the thickness of the longitudinal ciliary muscle. In an attempt to study how the tension of the ciliary muscle is transmitted to the inner wall of the Schlemm's canal, interconnections within the trabecular meshwork were also studied. The results indicate that after 40 weeks of gestation there is little or no further change with aging in the height of the scleral spur but there is a change in shape. The scleral spur is much less developed in monkey eyes than in human eyes. The corneoscleral meshwork predominates over the uveal meshwork in most human eyes while in monkey eyes the situation is the opposite. In man the thickness of the meridional part of the ciliary muscle attached to the scleral spur varies greatly in eyes with a well developed scleral spur. Interconnecting trabecular beams composed of elastic-like fiber were observed in the uveal and corneoscleral meshwork, as well as in the juxtacanalicular meshwork, extending to the cells of the inner wall of the Schlemm's canal. These findings and the dense structure of the scleral spur suggest that in monkey eyes, and at least in some human eyes, contraction of the ciliary muscle causes unfolding of the trabecular meshwork, not so much through the movement of the scleral spur as by movement of the interconnecting trabecular beams and fibers. One important role of the scleral spur is probably to keep the corneoscleral meshwork open when the ciliary muscle relaxes, and another is to enable inward-forward movement of the circular part of the ciliary muscle by pulling the posterior tip of the ciliary muscle anteriorly when the ciliary muscle contracts. A rigid scleral spur is an advantage for these two functions.

Adult↗
PubMed1988

Effects of alpha-chymotrypsin on the outflow routes for aqueous humor.

The anterior chamber was perfused with alpha-chymotrypsin, 50 micrograms ml-1, in mock aqueous humor in cynomolgus monkeys. The enzyme caused a marked rise in outflow facility and had clear effects on the structure of the outflow routes for aqueous humor. The intertrabecular spaces in the iridocorneal chamber angle were wider than normal, the openings in the uveal and corneoscleral meshwork appeared enlarged, there was ballooning of the juxtacanalicular region and the inner wall of Schlemm's canal into the canal and also splitting of the inner wall of the canal. The trabecular cells appeared relaxed with most of the cell processes retracted, some broken. There were discontinuities in the cell membrane and blebs. Parts of the trabecular beams were denuded. Two days after the enzyme treatment the facility was in the normal range, no splits in the inner wall of Schlemm's canal we observed but many of the other changes in structure remained. The number of invaginations in the inner wall of Schlemm's canal was markedly reduced after 2-18 days. A second and third perfusion with alpha-chymotrypsin caused a rise in outflow facility similar to the first. Some morphological changes remained 163 days after enzyme treatment. Pilocarpine a few days after alpha-chymotrypsin treatment caused a marked increase in outflow facility. The results suggest that alpha-chymotrypsin affects the glycoproteins of the cell membrane and as a result causes disorganization of the cytoskeleton, loss of loose adhesions and breaks of cell processes. The rapid recovery of the resistance to outflow was probably due to healing of the splits in the inner wall of Schlemm's canal; a marked reduction in the number of cells with invaginations suggests that in addition there may have been a reduction in the number of transcellular pores in the inner wall of Schlemm's canal.

Animals↗
PubMed1988

[Inhibitory effect and synergism of cernitin pollen extract on the urethral smooth muscle and diaphragm of the rat].

Inhibitory effects of cernitin pollen extract (CN-009), consisting of T-60 (a water-soluble extract) and GBX (an acetone-soluble extract) at a ratio of 20:1, were investigated in rat urethral smooth muscle and diaphragm. In the urethral smooth muscle, CN-009 (3.0 x 10(-4) approximately 3.0 x 10(-3) g/ml), T-60 and GBX (corresponding to CN-009) concentration-dependently inhibited the noradrenaline (NA, 10(-5) g/ml)-induced contraction. According to Bürgi's calculation, the inhibition by T-60 and GBX was synergistic. On the other hand, GBX inhibited the NA-contraction non-competitively and also inhibited the K+-contraction. In contrast, T-60 tended to inhibit competitively, but did not affect the K+-contraction. In the diaphragm, CN-009 (5.25 x 10(-3) approximately 2.1 x 10(-2) g/ml) concentration-dependently inhibited the nerve stimulation-induced twitch response. T-60 (corresponding to CN-009) showed no effect, while GBX slightly inhibited the twitch response. The effects of T-60 and GBX were synergistic. The inhibitory effects of CN-009 (2.1 x 10(-2) g/ml) and GBX (1.0 x 10(-2) g/ml) were specific against the nerve stimulation and were not antagonized by neostigmine (1.0 x 10(-5) g/ml). These results suggested that these effects were neither musculotropic nor competitive against ACh. In conclusion, CN-009 concentration-dependently inhibited the urethral contraction and the skeletal muscular twitch response. It was suggested that T-60 and GBX had different mechanisms and inhibited the response synergistically.

Animals↗
PubMed1988

A self-induced translation model of myosin head motion along thin filament in muscle contraction.

Evidence has been accumulating that muscle contraction may not be associated with the power stroke of the cross-bridges tightly coupled with ATP hydrolysis cycle. We have constructed a new contraction model which includes a number of basic properties of contraction processes not taken into consideration in the models hitherto reported. The basic assumption is that, when one head of a myosin molecule attaches to an actin monomer on thin filament, conformational changes take place in the neighbouring actin monomers to result in their non-symmetrical charge distribution to exert electrostatic force on the unattached head of the same myosin molecule in one direction. Thus, the unattached head moves along thin filament to attach to another actin monomer, while the already attached head detaches from thin filament. These steps are repeated to cause muscle contraction. The above contraction model can explain the results of our X-ray diffraction experiments as well as the results reported by other authors.

Actin Cytoskeleton↗