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S Higashi

Publications and source records attributed to S Higashi.

At least 73 records · Page 4Linked to original sources
PubMed1998

Evaluation of cytotoxicity of calcium phosphate cement consisting of alpha-tricalcium phosphate and dicalcium phosphate dihydrate.

A newly developed calcium phosphate cement, MM, was evaluated for tissue irritability by means of cell cultures. In this study, MM showed extensive mild cytotoxicity compared with other cements before setting. Inhibition of adhesion of L-929 cells was not observed after contact with MM for 24 hours. The influence of MM on colony formation was approximately the same as that of another calcium phosphate cement and less than that of a glass ionomer cement. Toxicity of MM after setting was compared with four cements; another calcium phosphate cement, glass ionomer cement, silicate cement and zinc oxide eugenol cement, but MM showed the least influence on cell morphology. Judging from these results, MM appears to be less cytotoxic than the cements in current use.

Animals↗
PubMed1998

[An experience with peeling technique with curettage of open mitral commissurotomy].

Ideally, the mitral valve is a soft, thin and flexible tissue. In severe rheumatic mitral stenosis, however, its motion is restricted due to the adhesion of fibrous tissues and calcium. Open mitral commissurotomy was not effective in successfully restoring it to normal condition. By using a peeling technique with curettage during open mitral commissurotomy, the calcium and fibrous tissues are sufficiently removed. This method is effective in improving the flexibility of the anterior leaflet of the restricted mitral valve.

Cardiac Surgical Procedures↗
PubMed1997

Purification and characterization of 25-hydroxyvitamin D3 1alpha-hydroxylase from rat kidney mitochondria.

We purified extensively 25-hydroxyvitamin D3 1alpha-hydroxylase (calcidiol, NADPH: oxygen oxidoreductase (1-hydroxylating), EC 1.14.13.13) from kidney mitochondria of rachitic rats and disclosed its peculiar properties as a P450. The final preparation was identified as a 55 kDa protein having an intense absorption at 417 nm characteristic of P450. The specific activity was 4.8 nmol/min/mg of protein indicating a 350-fold purification. Specific content of P450 was 1.1 nmol/mg of protein and turnover number was 4.4 min-1.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1997

Conformation of factor VIIa stabilized by a labile disulfide bond (Cys-310-Cys-329) in the protease domain is essential for interaction with tissue factor.

Unlike other trypsin-type serine proteases, zymogento-enzyme transition of conformation of factor VII apparently requires not only conversion of the zymogen to active form factor VIIa (VIIa) but also interaction of VIIa with tissue factor (TF). To determine the region of interaction that correlates with maturation of the VIIa active site, we modified intramolecular disulfide bonds in VIIa and examined the interaction of the modified VIIa with soluble TF (sTF). We found that partial reduction and S-carboxamidomethylation of disulfide bonds in VIIa led to losses of amidolytic activity and the binding ability to sTF. To determine the sites of modification that associate with the loss of functions, partially S-carboxamidomethylated VIIa was separated on a column of immobilized sTF. Each of the sTF-bound and sTF-unbound fractions and native VIIa was then digested by trypsin, and the digest was analyzed by reversed-phase high performance liquid chromatography. We found that reduction and S-carboxamidomethylation of a disulfide bond between Cys-310 and Cys-329 in the protease domain of VIIa led to loss of the binding ability with sTF, and the modification of a disulfide bond between Cys-340 and Cys-368 of VIIa led to loss of the amidolytic activity. In the three-dimensional structures of trypsinogen and trypsin, the disulfide bonds corresponding to Cys-340-Cys-368 and Cys-310-Cys-329 of VIIa are, respectively, in and adjacent to the activation domain, which has flexible conformation in trypsinogen but not in trypsin. Furthermore, the crystal structure of human VIIa.TF complex indicates that the region next to Cys-310-Cys-329 is in contact with sTF. We speculate that a regional flexibility, reflected by the labile nature of disulfide bonds of Cys-310-Cys-329 and Cys-340-Cys-368 in the protease domain, contributes to the inability of VIIa to attain the active conformation. Interaction of TF with this flexible region may stabilize the structure in a conformation similar to that of the active state of VIIa.

Amino Acid Sequence↗
PubMed1997

Low-temperature-induced desaturation of fatty acids and expression of desaturase genes in the cyanobacterium Synechococcus sp. PCC 7002.

Changes in response to temperature of lipid classes, fatty acid composition and mRNA levels for acyl-lipid desaturase genes were studied in the marine unicellular cyanobacterium, Synechococcus sp. PCC 7002. The degree of unsaturation of C18 fatty acids increased in cells grown at lower temperature for all lipid classes, and omega 3 desaturation occurred specifically in cells grown at low temperature. While the level of 18:1(9) fatty acids declined, desaturation at the omega 3 position of C18 fatty acids increased gradually during a 12-h period after a temperature shift-down to 22 degrees C. However, the mRNA levels of the desA (delta 12 desaturase), desB (omega 3 desaturase) and desC (delta 9 desaturase) genes increased within 15 min after a temperature shift-down to 22 degrees C; the desaturase gene mRNA levels also rapidly declined within 15 min after a temperature shift-up to 38 degrees C. Therefore, the elevation of mRNA levels for the desaturase genes is not the rate-limiting event for the increased desaturation of membrane lipids after a temperature shift-down. The rapid, low-temperature-induced changes in mRNA levels occurred even when cells were grown under light-limiting conditions for which the growth rates at 22 degrees C and 38 degrees C were identical. These studies indicate that the ambient growth temperature, and not some other growth rate-related process, regulates the expression of acyl lipid desaturation in this cyanobacterium.

Cold Temperature↗
PubMed1997

Stop and branch behaviors of geniculocortical axons: a time-lapse study in organotypic cocultures.

The behavior of growing thalamic axons was studied in an organotypic coculture of the lateral geniculate nucleus (LGN) with the visual cortex (VC) to reveal cellular interactions that underlie the formation of lamina-specific thalamocortical connections. The LGN explant was placed at the ventral side, pial surface, or lateral edge of the VC explant, and fluorescent dye-labeled LGN axons were observed by confocal microscopy in fixed and living tissue. The axonal projection pattern in fixed cocultures after 1 week in vitro demonstrated that, in all three configurations, LGN axons formed primitive branches mainly in layer 4. A time-lapse study further examined axonal growth and branch formation in the living cortical explant. The majority of branches emerged within layer 4 behind the axonal tip, regardless of the direction of axonal entry. In addition, most axons entering from the ventral or pial side of the VC exhibited a transient or persistent stop of axonal growth in and around layer 4, whereas those entering from the lateral edge of the VC traveled along layer 4 without exhibiting stop behavior. The axonal stop often was accompanied by growth cone collapse and a slight retraction. These results suggest the existence of branch and stop cues in layer 4 of the cortex that are recognized by LGN axons.

Animals↗
PubMed1997

Activation of cytosolic phospholipase A2 by platelet-derived growth factor is essential for cyclooxygenase-2-dependent prostaglandin E2 synthesis in mouse osteoblasts cultured with interleukin-1.

The synthesis of prostaglandins (PGs) is regulated by the arachidonic acid release by phospholipase A2 (PLA2) and its conversion to PGs by cyclooxygenase (COX). In the present study, we examined the regulation of PG synthesis by interleukin (IL)-1alpha in primary mouse osteoblastic cells isolated from mouse calvaria. Although IL-1alpha greatly enhanced cox-2 mRNA expression and its protein levels, PGE2 was not produced until 24 h. When arachidonic acid was added to osteoblastic cells precultured with IL-1alpha for 24 h, PGE2 was produced within 10 min. Of several growth factors tested, platelet-derived growth factor (PDGF) specifically initiated the rapid synthesis of PGE2, which was markedly suppressed by a selective inhibitor of cox-2 (NS-398). In mouse osteoblastic cells, cytosolic PLA2 (cPLA2) mRNA and its protein were constitutively expressed and increased approximately 2-fold by IL-1alpha, but secretory PLA2 mRNA was not detected. PDGF rapidly stimulated PLA2 activity, which was blocked completely by a cPLA2 inhibitor (arachidonyltrifluoromethyl ketone). The PDGF-induced cPLA2 activation was accompanied by phosphorylation of its protein. These results indicate that cox-2 induction by IL-1alpha is not sufficient, but cPLA2 activation by PDGF is crucial for IL-1alpha-induced PGE2 synthesis in mouse osteoblasts.

Animals↗
PubMed1997

Sex difference in serum 7 alpha-hydroxycholesterol levels in the rat reflect hepatic activity of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase and cholesterol 7 alpha-hydroxylase.

Factors that affect serum levels of 7 alpha-hydroxycholesterol were studied in the rat. Serum levels of 7 alpha-hydroxycholesterol differed in male and female rats fed regular chow (male; 0.2 +/- 0.1 nmol/ml (mean +/- SD); n = 8; female; 0.4 +/- 0.1 nmol/ml; n = 8). When rats were fed with chow to which 3% cholestyramine had been added, the level increased significantly, particularly in female rats (male; 0.6 +/- 0.3 nmol/ml; n = 8; female; 2.4 +/- 1.5 nmol/ml; n = 8). The liver activity of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme for degradation of cholesterol, did not show any sex differences, irrespective of whether the animals were fed with regular chow (male; 51 +/- 15 pmol/min per mg protein; n = 8; female; 58 +/- 21 pmol/min per mg protein; n = 8), or the cholestyramine-supplemented chow (male; 162 +/- 33 pmol/min per mg protein; n = 8; female; 172 +/- 33 pmol/min per mg protein; n = 8). In contrast, the activity of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase, which acts after cholesterol 7 alpha-hydroxylase in the catabolism of cholesterol, showed a marked difference between the sexes. In both sexes this enzyme activity was higher in cholestyramine-treated rats (male; 963 +/- 78 pmol/min per mg protein; n = 8; female; 708 +/- 106 pmol/min per mg protein, n = 8) compared to that in that rats received regular chow (male; 622 +/- 83 pmol/min per mg protein; n = 8; female; 469 +/- 41 pmol/min per mg protein; n = 8). If the serum level of 7 alpha-hydroxycholesterol depended solely on the enzyme activity of cholesterol 7 alpha-hydroxylase, it would be difficult to explain these sex differences, since there were no sex differences in levels of cholesterol 7 alpha-hydroxylase. These results clearly indicate that, in the rat, the serum level of 7 alpha-hydroxycholesterol depends not only on cholesterol 7 alpha-hydroxylase activity but also on 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

[Severe acute cardiac failure caused by the combination of the aortic stenosis and sudden onset of the mitral chordae rupture].

The patient, who had an aortic stenosis, suddenly complicated with severe acute cardiac failure. The rupture of the mitral chordae tendineae was detected by the echocardiogram. Double replacements (aortic and mitral) were done immediately after the onset of chordae rupture. This condition, combination of aortic stenosis and sudden onset of chordae rupture, always results in severe heart failure which is explained by the combination of pressure and volume loading. Finally the emergent operation is believed to be an only solution for this situation.

Acute Disease↗
PubMed1997

[Evaluation of neuro-Behçet disease with 99mTc-HMPAO brain SPECT: comparison with MR imaging].

The purpose of this study was to evaluate the brain perfusion of neuro-Behçet disease using 99mTc-HMPAO. In total, nine patients (7 men and 2 women) were evaluated. Seven were in the chronic phase, one was acute and the other was subacute. The results of perfusion study were compared with the MRI findings. The findings of chronic-phase neuro-Behçet disease were as follows: 99mTc-HMPAO showed hypoperfusion of the cerebellum in 3, brain stem in 5, and cerebral cortex in 4 patients. Moreover, asymmetry of the basal ganglia and thalamus was seen in 4 cases with 99mTc-HMPAO. MRI showed atrophy of the cerebellum in 4, brain stem in 5 and cerebral cortex in 2 patients. One acute patient showed a perfusion defect with 99mTc-HMPAO that was consistent with the vasculitis shown with MRI. In the remaining subacute patient, perfusion defect was demonstrated with 99mTc-HMPAO, consistent with the infarction shown with MRI. It is concluded that brain perfusion scintigraphy is useful to evaluate the brain blood flow of neuro-Behçet disease.

Adult↗
PubMed1997

[Calcification of cervical ligamentum flavum--analysis of calcium compounds and histopathological findings].

We operated 3 patients with cervical myelopathy due to calcification of ligamentum flavum (CLF). Specimens collected surgically were subjected to X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy (Raman) analysis and also histopathological examination. The calcium compounds deposited were calcium pyrophosphate dihydrate (CPPD) in Case 1, apatite in Case 2, and a double-layer structure with an outer CPPD layer and an inner carbonate apatite layer in Case 3. Histopathologically, CPPD deposition in Case 1 could be distinguished from apatite deposition in Case 2 and 3 by hematoxylin-eosin stain. Chondrocytes were observed in all 3 cases, suggesting the chondrocytes may have played a role in calcification in these three cases. To date, 62 cases of CLF (including the present cases) have been reported, and analysis of calcium compound has been performed for 29 of them. Of these 29, 15 were analyzed as calcium phosphate compounds, 9 as CPPD and 4 cases as mixed crystals like Case 3. However the analysis method and result about CPPD are no problem, the analysis result of calcium phosphate compounds depends on the using methods. Calcium phosphate or undetectable compounds was identified by XRD as hydroxyapatite (HAp), and by FTIR as calcium phosphate or undetectable compound. Analysis of calcium phosphate compounds should be condacted and identified by XRD, FTIR, and Raman. We propose two possible mechanisms for the formation of the double-layer structure in Case 3: one is formation of apatite first followed by deposition of CPPD outside, and the other is formation of CPPD first followed by conversion of CPPD in the central region to apatite. What the process of formation of the double-layer was in this cases remains unclear.

Aged↗
PubMed1996

Protein and RNA synthesis-dependent and -independent LTPs in developing rat visual cortex.

Multiple forms of synaptic potentiation have been described, but their involvement in development versus learning is unknown. To address this, we examined whether long-term potentiation (LTP) in visual cortex requires protein or RNA synthesis using slice preparations. Theta-burst stimulation of white matter induced two distinct types of LTP in layer 4. A slowly developing LTP, preferentially induced in juveniles, was blocked by protein and RNA synthesis inhibitors and was L-type calcium channel dependent. A quickly developing LTP, induced in juveniles and adults, was independent of macromolecular synthesis and required N-methyl-D-aspartate receptor activation. Thus, slow LTP might account for developmental plasticity in visual cortex including the activity-dependent refinement of neural circuitry while fast LTP might underlie the changes in synaptic strength that may participate in visual learning and memory.

2-Amino-5-phosphonovalerate↗
PubMed1996

Molecular mechanism of tissue factor-mediated acceleration of factor VIIa activity.

The mechanism of the acceleration of the catalytic activity of factor VIIa (VIIa) in the presence of tissue factor (TF) was investigated. To explore the VIIa's site(s) that correlates with TF-mediated acceleration, zymogen VII, VIIa, and active site-modified VIIa were prepared, and dissociation constants (Kd) for their bindings to TF or soluble TF in solution were determined. We found that conversion of zymogen VII to VIIa led to an increase in affinity (DeltaDeltaG = 4.3-4.4 kJ/mol) for TFs. Dansyl-Glu-Gly-Arg chloromethyl ketone (DNS-EGRck) treatment of VIIa led to a further increase in the affinity (DeltaDeltaG = 7.3-12 kJ/mol). Neither removal of the Gla domain from VIIa nor truncation of the COOH-terminal membrane and cytoplasmic regions of TF affected the affinity enhanced after DNS-EGRck treatment of VIIa. Treatment of VIIa with (p-amidinophenyl)methanesulfonyl fluoride also enhanced its affinity for soluble TF, whereas treatment with 4-(2-aminoethyl)benzenesulfonyl fluoride, phenylmethylsulfonyl fluoride, or diisopropyl fluorophosphate had a slight effect on the affinity. On the other hand, DNS-EGRck and (p-amidinophenyl)methanesulfonyl fluoride treatments, but not diisopropyl fluorophosphate treatment, of VIIa led to protection of its alpha-amino group of Ile-153 from carbamylation. Protection of the alpha-amino group was consistent with formation of a critical salt bridge between Ile-153 and Asp-343 in the protease domain of VIIa. Therefore, TF may preferentially bind to the active conformational state of VIIa. When one assumes that free VIIa exists in equilibrium between minor active and dominant zymogen-like inactive conformational states, preferential binding of TF to the active state leads to a shift in equilibrium. We speculate that TF traps the active conformational state of VIIa and converts its zymogen-like state into an active state, thereby accelerating the VIIa activity.

Amino Acid Chloromethyl Ketones↗
PubMed1996

Morphology of individual axons in crossed corticorubral projections in developing cats and effects of partial denervation.

Ordered neuronal connections in mature brains are thought to be sculpted from initially diffuse projections by elimination of inappropriate projections and strengthening of appropriate ones. Although evidence suggests that neuronal activity plays a role in these processes, the mechanism behind the modification of neuronal connections remains obscure. To gain insight into the mechanisms of axonal elimination and projection strengthening, we examined the morphology of individual axons that were to be eliminated as well as the consequences of partial denervation. While corticorubral projections in adult cats are thought to be uncrossed, early in postnatal development and after early unilateral lesions to the sensorimotor cortex, however, a significant amount of crossed corticorubral projections occurs. We examined the morphology of individual corticorubral axons in fetal cats and kittens from embryonic day 59 to postnatal day 48 and those that had received early unilateral lesions to the cortex, by serial reconstruction of Phaseolus-vulgaris-leucoagglutinin- or biocytin-labeled axons. For about 2 weeks during pre- and postnatal development, crossed axons remained simple in morphology, with few branches. Thereafter, they showed an increase in branch number, but then began to show fewer branches again. Axons and their collaterals were found in nonrestricted areas of the red nucleus (RN) throughout the period of observation, indicating that axons can sit at an inappropriate target for weeks but fail to ramify. In contrast, crossed corticorubral axons in kittens with cortical lesions showed terminal-arbor-like structures in the RN region that are in mirror symmetry to topographically appropriate areas in the ipsilateral RN, although some showed simple morphology without arbors. These complicated forms of morphology of individual axons during development and after partial denervation may not be explained by a simple activity-dependent mechanism.

Animals↗