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Biomedical subjects

N Higuchi

Publications and source records attributed to N Higuchi.

At least 37 records · Page 2Linked to original sources
PubMed1999

A survey of filling methods, intracanal medications, and instrument breakage.

The present survey was conducted to obtain answers to some basic questions regarding the use of intracanal medications, root canal filling methods, and the intracanal breakage of instruments. A letter was sent to 300 endodontists listed in the 1995-1996 membership roster of the American Association of Endodontists. Eighty-five replies were received. Calcium hydroxide as an intracanal medication was used by 91.7% of the responding endodontists. With regard to the root canal filling technique, 52.9% used the lateral condensation method. When intracanal breakage occurred, 95.3% of the respondents informed the patient. The results of this survey provide useful information for the education of undergraduate dental students.

Calcium Hydroxide↗
PubMed1998

Changes in the carbon balance of tropical forests: evidence from long-term plots

The role of the world's forests as a "sink" for atmospheric carbon dioxide is the subject of active debate. Long-term monitoring of plots in mature humid tropical forests concentrated in South America revealed that biomass gain by tree growth exceeded losses from tree death in 38 of 50 Neotropical sites. These forest plots have accumulated 0.71 ton, plus or minus 0.34 ton, of carbon per hectare per year in recent decades. The data suggest that Neotropical forests may be a significant carbon sink, reducing the rate of increase in atmospheric carbon dioxide.

Journal Article↗
PubMed1996

Thoracoscopic en bloc total esophagectomy with radical mediastinal lymphadenectomy.

OBJECTIVE: Total esophagectomy with en bloc mediastinal lymphadenectomy for cancer carries a substantial morbidity and mortality rate. To investigate the feasibility of thoracoscopic technique, we carried out an extensive laboratory study. Encouraged by our excellent results, we conducted a clinical trial. METHODS: From September 1994 to September 1995, 39 patients thoracic esophageal cancer lesions not invading surrounding organs underwent total esophagectomy with mediastinal lymphadenectomy by means of thoracoscopy. Ages ranged from 47 to 86 years. The procedures were conventional except for the thoracic portion, which was performed as a thoracoscopic procedure with six trocar holes instead of thoracotomy. All harvested lymph nodes were counted for each station. Spirometric data and plethysmographically determined vital capacity were measured before and after operation for all patients. RESULTS: All procedures were accomplished as scheduled, and none was converted to open thoracotomy. The operating time was 200 +/- 41 minutes (mean +/- standard deviation). Estimated blood loss was 270 +/- 157 ml. The harvested lymph nodes numbered 19.7 +/- 11.1 per patient. Seventeen patients (45%) had positive lymph nodes. There were no in-hospital deaths within 30 days. Twenty-two patients did not require postoperative ventilatory support. Vital capacity decreased to 85% +/- 11% of the preoperative values, and forced expiratory volume in 1 second decreased to 82% +/- 16%. CONCLUSIONS: Thoracoscopic mediastinal lymphadenectomy is technically feasible, and its completeness is comparable to that of the open technique. The decline in pulmonary function is significantly less than that seen in our previous experience with the open technique.

Aged↗
PubMed1996

[Home care that meets the wishes of patients with terminal stage cancer and their families].

As our ward is a general surgical ward, we formerly had difficulties providing appropriate care for patients with terminal cancer. To solve the problem, we have formed a nursing study group in order to provide home care that would meet the wishes of such patients and their families. Our specific approach was as follows: 1) preparation of a form on which patient information is collected; 2) a support system for home care (such as pain control and home parenteral nutrition; and 3) a solid collaboration system between ward nurses and visiting nurses. Such a program enables us to understand the wishes of patients and families and to provide various support where needed. The project helps to lessen the anxiety and the burden that patients and families feel in home care, and improve the quality of life (QOL).

Aged↗
PubMed1995

[CT anatomy of the caudate lobe of the liver].

The anatomy of the portal vein branches in the caudate lobe of the liver was studied in 20 patients by double-phase CT arterial portography (DP-CTAP). DP-CTAP provided excellent images of the portal venous system in the first phase and the perfusion defects of intrahepatic tumors in the second phase. From DP-CTAP images of the first phase, a sufficient number of interpolated images were created for a smooth paging display. The ramifying structures of the portal system were traced on the monitor using the tracking ball. This method was found to be very effective and reliable for the anatomical assessment of the caudate lobe. The number and origins of the caudal portal branches were investigated in each case, and the caudate lobe of the liver could be divided into right and left segments.

Humans↗
PubMed1993

[CT angiography of the liver].

The diagnostic efficacy of CT arterial portography (CTAP) for the hepatic tumors has been established. We developed the double-phase incremental CTAP (DP-CTAP) using a fast CT scanner, by which the double-phase scanning of the whole liver was made during a single contrast administration. The DP-CTAP was performed in 9 cases of hepatic diseases, and was useful for the lesion detection and improvement of the visualization of the liver vasculatures. The maximum density projection angiogram of the portal and hepatic veins was easily made by DP-CTAP images, and useful for three dimensional understanding of the liver vasculatures and the detection of the vascular abnormalities.

Humans↗
PubMed1993

[Fast spin echo MRI techniques. Contrast characteristics and clinical potentials].

Based on partial RF echo planar principles, Fast Spin Echo techniques (FSE) were implemented on high field systems. These methods produce image quality and contrast which resemble to conventional spin echo (SE) techniques. By reducing acquisition times by factors between 1.4 and 16 over SE methods, FSE allows for several imaging options usually prohibitive with conventional spin echo (SE) sequences. These include fast scans (especially breath-hold acquisitions); improved T2 contrast with longer TR intervals; increased spatial resolution with the use of larger image matrices and/or smaller fields of view; and 3D volume imaging with a 3D multislab FSE technique. Contrast features of FSE techniques are directly comparable to those of multiple echo SE sequences using the same echo spacing than FSE methods. However, essential contrast differences existing between the FSE sequences and their routine asymmetric dual SE counterpart can be identified. Decreased magnetic susceptibility effects and increased fat signal present within T2 weighted images compared to conventional dual SE images are due to the use of shorter echo spacings employed in FSE sequences. Off-resonance irradiation inherent to the use of a large number of radio frequency pulses in shown to results in dramatic magnetization contrast transfer effects in FSE images acquired in a multislice mode.

Abdomen↗
PubMed1992

A novel method for fat suppression in RARE sequences.

Rapid acquisition relaxation-enhanced (RARE) sequences (Hennig et al., Magn. Reson. Med. 3, 823 (1986)) utilize one or several Carr-Purcell-Meiboom-Gill (CPMG) echo trains to sample a number of k-space lines each repetition time TR. The technique can rapidly generate multislice T2-weighted images which, as a rule, are strikingly similar in contrast to conventional T2-weighted spin-echo (SE) images. An exception to this rule is the appearance of very bright signal from fat in T2-weighted RARE images as compared to conventional T2-weighted SE images. To reduce this fat signal, we introduce a time delay, tau c, between the 90 degrees x and first 180 degrees y pulse of each echo train such that a phase angle of pi/2 develops between fat and the reference (water) line at echo maxima. The technique leads to single-acquisition fat suppression without the use of frequency-selective saturation pulses and concomitant loss of slices per TR. A Bloch equation analysis is used to identify two major mechanisms contributing to suppression of off-resonance spins such that w tau c = pi/2. Namely, the CPMG sequence becomes a CP sequence with no self-correction properties for imperfect 180 degrees pulses leading to enhanced signal decay, and the raw k-space data matrix become segmented into blocks alternately multiplied by +/- i, leading to signal dispersion following Fourier transformation.

Abdomen↗
PubMed1992

Magnetic resonance imaging of the acute effects of interstitial neodymium:YAG laser irradiation on tissues.

RATIONALE AND OBJECTIVES: Laser irradiation therapy in deep tissues requires a monitoring method other than visual guidance. Magnetic resonance imaging (MRI) can be used for this purpose because it visualizes soft tissue structures and heat distribution. METHODS: The authors performed interstitial laser irradiations in rat livers with various laser outputs and measured the sizes of laser-induced lesions. MRI of these lesions was done ex vivo and compared with the histologic findings. Laser-induced lesions also were studied in rabbit brain, liver, and skeletal muscle to show the influences of tissue optical and thermal properties. Imaging of interstitial laser irradiation also was performed in vivo in rabbit brains. RESULTS: MRI depicted the laser-induced lesions produced with different laser outputs and tissue types. MRIs of rabbit brain in vivo effectively demonstrated the signal decrease during heating and acute tissue changes. CONCLUSION: MRI has potential for monitoring interstitial laser surgery or hyperthermia.

Animals↗
PubMed1991

Sonographic assessment and grading of spleen size.

Ultrasonography was used to evaluate spleen size in patients with various clinical conditions including those of the liver, blood, collagen, or autoimmune disease. To express spleen size, a spleen index (SI), the product of the transverse diameter and its perpendicular diameter measured on the maximum cross-sectional image of the spleen, was used. SI correlated well with the volumes of resected spleens. Splenomegaly was present in high percentages of patients with liver, blood, collagen, and autoimmune disease, even though a majority of these spleens were not large enough to palpate. By grading the SI, characteristic distributions of SI were obtained for patients with different types of diseases. Obtaining and grading the SI by the use of ultrasound appears to be a significant supplemental aid for evaluating spleen size, especially in patients whose spleens are not palpable.

Adolescent↗
PubMed1991

Real-time magnetic resonance imaging of laser heat deposition in tissue.

We applied diffusion-sensitive echo planar (Instascan) imaging to study thermal changes caused by a Nd:YAG laser. Images of phantom materials and normal rabbit brain tissue in vivo, acquired in 150 ms, every 2s, clearly showed the dynamics of temperature-related signal intensity changes in the regions irradiated by the laser.

Animals↗
PubMed1991

Stimulation of vitellogenesis by pyrethroids in mated and virgin female adults, male adults, and fourth instar females of Ornithodoros moubata (Acari: Argasidae).

The effects of several pyrethroids on vitellogenesis, i.e., vitellogenin (Vg) synthesis and ovarian development in unfed mated female adults of Ornithodoros moubata were investigated. Survival of ticks treated with pyrethrin, resmethrin, and etophenprox was very low. Ticks treated with cypermethrin (CyM), fenvalerate (Fev), and flucythrinate (Flu) survived even when high concentrations were used. Vg titer in the hemolymph of unfed mated females was the same level on day 5 and about three times higher on day 10 after treatment with CyM, Fev, and Flu, as that of engorged adult females. CyM was the most effective in inducing vitellogenesis and was further evaluated in unfed virgin females, males, and fourth instars. CyM was shown to stimulate vitellogenesis in unfed virgin females adults. Oviposition did not occur but ovaries were well developed. CyM also was shown to stimulate Vg in the hemolymph of unfed and fed adult males; however, the Vg levels were very low compared to that of engorged adult females. Extremely high concentrations of Vg were observed in the hemolymph of female nymphs (fourth instar), particularly engorged nymphs, treated with CyM (10 micrograms). No ovarian development was observed in these nymphs. Vg stimulated by CyM was shown to be immunologically and electrophoretically the same as that of normal engorged females.

Animals↗
PubMed1991

Synthesis and inhibitory activity of acyl-peptidyl-pyrrolidine derivatives toward post-proline cleaving enzyme; a study of subsite specificity.

Several pyrrolidine derivatives have been synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain. Almost all the compounds tested in this study inhibited the activity of both enzymes at low IC50 values (from nM to microM) but a specificity difference was observed with alkylacyl-peptidyl-pyrrolidine derivatives which strongly inhibited only the bacterial enzyme. The most effective inhibitors have a proline residue on their P2 sites and a substituted or unsubstituted phenoxybutyryl moiety on their P3 sites. Thus phenoxybutyryl-prolyl-pyrrolidine is the most effective partial structure of the inhibitors. The best inhibitors found were: 4-(4-benzylphenoxy)butyryl-prolyl-pyrrolidine for bacterial enzyme (IC50 1.4 nM) and 4-phenylbutyryl-thioprolyl-pyrrolidine for bovine brain enzyme (IC50 67 nM). In the passive avoidance test, using amnesic rats experimentally induced with scopolamine, the pyrrolidine derivatives which had potent inhibitory activity toward post-proline cleaving enzymes also showed strong anti-amnesic activities at doses of 1-5 mg/kg, i.p.

Acylation↗
PubMed1990

Quantitative analysis of antiatherosclerotic effect of nifedipine in cholesterol-fed rabbits.

Reports concerning the effect of slow calcium-channel blockers on experimental atherosclerosis are controversial. We examined the antiatherosclerotic effect of nifedipine (40 mg/day for 16 weeks) on aorta of rabbits on diets containing 0.3%, 0.5%, and 1.0% cholesterol. There were no significant differences in levels of serum lipids with or without nifedipine in the same cholesterol-fed rabbits. The results obtained show that nifedipine suppressed the extent of lipid deposition and surface involvement (S.I.) in aorta in 0.3% cholesterol-fed rabbits, whereas nifedipine only tended to suppress S.I. in 0.5% cholesterol-fed rabbits and had no effect in 1.0% cholesterol-fed rabbits. The log dose-response relationship of S.I. was obtained by plotting the concentration of cholesterol in the feed or the "integrated value" of the total serum cholesterol (TC), i.e., the cumulative sum of the serum TC values obtained at each week. The log dose-response curve was shifted in parallel with the right in nifedipine groups. The Lineweaver-Burk plot constructed from the dose-response curve had the same points crossing the ordinate with or without nifedipine. These results suggested that nifedipine suppressed S.I. in a competitive manner with cholesterol on the specific binding site of lipid deposition. Electron-microscopic findings also demonstrated that fat droplets in smooth muscle cells, extracellular matrix containing collagen, and elastic fibers decreased in nifedipine-treated rabbits.

Animals↗
PubMed1990

Synthesis and inhibitory activity of acyl-peptidyl-prolinalderivatives toward post-proline cleaving enzyme as nootropic agents.

Several prolinal derivatives were synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain and their possible properties as nootropic agents. Almost all the compounds tested inhibited the activity of both enzymes at low IC50 values of the order of nM, but a specificity difference was observed with alkylacyl-prolinal derivatives which strongly inhibited only the bacterial enzyme. Prolyl-prolinal derivatives were the most effective inhibitors for both enzymes. In the passive avoidance test using amnesic rats experimentally induced with scopolamine, the prolinal derivatives that have potent inhibitory activity toward post-proline cleaving enzymes showed also strong anti-amnesic activities at dose of 10-1000 micrograms/kg, i.p. Some of the compounds showed a bell-shape dose dependency. These results suggest that the post-proline cleaving enzymes play an important role in the regulation of learning and memory consolidation in the brain and inhibitors of these enzymes are suggested as possible candidates for nootropic agents, particularly for an anti-amnesic drug.

Amino Acid Sequence↗
PubMed1990

Inhibitory effect of di- and tripeptidyl aldehydes on calpains and cathepsins.

Eight different di- and tripeptidyl aldehyde derivatives, each having at its C-terminus an aldehyde analog of L-norleucine, L-methionine, or L-phenylalanine with a preceding L-leucine residue, were synthesized and tested for their inhibitory effects on several serine and cysteine endopeptidases. These compounds showed almost no inhibition of trypsin, and only weak inhibition of alpha-chymotrypsin and cathepsin H, while they exhibited marked inhibition of cathepsin B less than calpain II congruent to calpain I less than cathepsin L, being stronger in this order. The mode of inhibition of these cysteine proteinases was competitive for the peptide substrate used and inhibitor constants (Ki) were calculated from the Dixon plot. The best inhibitors found were: 4-phenyl-butyryl-Leu-Met-H for calpain I (Ki, 36 nM) and calpain II (Ki, 50 nM); acetyl-Leu-Leu-nLeu-H for cathepsin L (Ki, 0.5 nM); acetyl-Leu-Leu-Met-H for cathepsin B (Ki, 100 nM).

Aldehydes↗