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Biomedical subjects

S Aoki

Publications and source records attributed to S Aoki.

At least 163 records · Page 9Linked to original sources
PubMed1998

Three-dimensional tomography using a soft X-ray holographic microscope and CCD camera.

The depth resolution of a soft X-ray hologram is much worse than its transverse resolution because a single soft X-ray hologram has a small numerical aperture. To obtain a three-dimensional image, in-line holograms of a specimen were recorded from various directions and reconstructed to obtain two-dimensional projection data. Then, a three-dimensional reconstruction was performed by back-projection of these reconstructed holograms. Three-dimensional images of a tungsten wire of diameter 10 micro m and a fossil of a diatom were obtained.

Journal Article↗
PubMed1998

Development of an ultra-fast data-acquisition system for a two-dimensional microstrip gas chamber.

A high-performance data-acquisition system has been developed in order to obtain time-resolved sequential images from a two-dimensional microstrip gas chamber (MSGC). This was achieved using fully digital processing with a synchronized pipeline method. Complex logical circuits for processing large numbers of signals are mounted on a small number of complex programmable logic devices. The system is operated with a 10 MHz synchronous clock, and has the capability of handling more than 3 x 10(6) counts s(-1) for asynchronous events. The system was examined using a 5 x 5 cm MSGC and the recently developed 10 x 10 cm MSGC (1024 outputs); the anticipated performances were achieved.

Journal Article↗
PubMed1998

X-ray polarimetry with the microstrip gas chamber.

A two-dimensional microstrip gas chamber (MSGC) with a 5 cm x 5 cm detection area has been developed. It has 254 anodes and 255 back strips, both with 200 micro m pitches. Using this MSGC, linear polarization of X-rays was successfully measured in the energy range 6-14 keV. In addition, the performance of the MSGC as an X-ray imaging polarimeter has been simulated using the EGS4 program (Electron Gamma Shower, Version 4) modified for this purpose. In this article, the results of both the polarization measurement and the simulation are reported.

Journal Article↗
PubMed1998

Development of a MicroStrip Gas Chamber as a Time-Resolved Area Detector.

A two-dimensional microstrip gas chamber (MSGC) has been developed with a 10 cm-square detection area and an ultrafast read-out system. The MSGC was made using multi-chip module (MCM) technology, and has a very thin substrate of 17 micro m and many anodes and back strips, both with 200 micro m pitches. The new read-out system, in which the hit addresses of the electrodes were sequentially encoded to the hit positions by a synchronous clock, handles data rates of up to 10(7) events s(-1) from MSGCs. This enables the acquisition of fast and sequential digital images. Furthermore, since the MSGC is a real photon-counting detector, the timing of the photons, to an accuracy of a few tens of nanoseconds, and energy can be recorded. Here, the performance of the MSGC system as a real-time area detector is reported, and the abilities of this system are discussed.

Journal Article↗
PubMed1998

Hepatocyte growth factor plays a dual role in regulating skeletal muscle satellite cell proliferation and differentiation.

The role of hepatocyte growth factor (HGF) and its receptor, c-met, in proliferation and differentiation of satellite cells was studied in primary cultures of chicken skeletal muscle satellite cells and a myogenic C2 cell line. HGF mRNA was expressed mainly in the myotubes of both cultures. The addition of conditioned medium derived from those cultures had a scattering effect on the canine kidney epithelial cell line, MDCK. In contrast, c-met mRNA levels decreased during cell differentiation of C2 and primary satellite cells. Application of exogenous HGF to chicken myoblasts resulted in their enhanced DNA synthesis. Among several growth factors, HGF was the first to induce DNA synthesis in quiescent satellite cells, thereby driving them into the cell cycle. Ectopic expression of chicken HGF in primary satellite cells suppressed the activation of muscle-regulatory gene reporter constructs MCK-CAT, MRF4-CAT, MEF2-CAT and 4Rtk-CAT, as well as the gene expression of MyoD and myogenin, and MHC protein expression. Ectopic MyoD reversed HGF's inhibitory effect on MCK transactivation. These data suggest that HGF inhibits cell differentiation by inhibiting the activity of basic helix-loop-helix (bHLH)/E protein heterodimers, thus inhibiting myogenic determination factor activity and subsequent muscle-specific protein expression. During muscle growth and regeneration, HGF plays a dual role in satellite-cell myogenesis, affecting both the proliferation and differentiation of these cells in a paracrine fashion.

Animals↗
PubMed1998

Clinicopathological features of chronic inflammatory demyelinating polyradiculoneuropathy in childhood.

The clinical, electrophysiological, and pathological findings, and the therapeutic characteristics in ten children with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), whose onset age was less than 16 years, were evaluated. The clinical progression pattern of the initial phase divided the patients into two groups. One group (six patients) showed a subacute progression for up to 2 months after onset and a subsided progression over 3 months. Three patients in this group had a preceding febrile episode. The other group (four patients) showed a chronic insidious progression for more than 3 months. The former group of patients revealed a favourable response to corticosteroid therapy as compared with the latter group. However, other clinical and laboratory features at the peak impairment were not distinguishable between these two groups. Motor dominant neuropathy was common to all patients, and only three cases showed sensory disturbance on the distal limbs. No cases revealed cranial nerve involvement. Motor and sensory nerve conduction and sural nerve biopsy studies revealed the demyelinating nature of the neuropathy. These clinicopathological features suggest that the subacute progression form frequently associated with prodromal episode and rather favourable corticosteroid response is characteristic in childhood CIDP, while the chronic insidious progression form is indistinguishable from the common adult CIDP.

Adolescent↗
PubMed1998

Three-dimensional ultrasonographic assessments of fetal development.

OBJECTIVE: To visualize fetal surface anatomic structures in advancing gestation by use of three-dimensional ultrasonography with a specially developed abdominal three-dimensional transducer. METHODS: One hundred six normal fetuses from 9 to 40 weeks' gestation were studied with a specially developed abdominal three-dimensional transducer (3.5 MHz). This imaging system can provide conventional two-dimensional ultrasonography images and also can generate within seconds high-quality three-dimensional images in the surface and transparent modes with no need for an external workstation. We determined percentage of surface anatomic structures visualized at each trimester using two-dimensional and three-dimensional ultrasonography. RESULTS: The number and the clarity of surface anatomic structures increased from the first to the third trimester of pregnancy. The image quality was less distinct in the first trimester because of the small fetal size. The ability to view the fetal face, hands, and feet was better with three-dimensional ultrasonography than with two-dimensional ultrasonography in the first trimester (P < .05), whereas fetal genitals were viewed better with two-dimensional ultrasonography than with three-dimensional ultrasonography in the second and third trimesters (P < .05). CONCLUSION: Three-dimensional ultrasonography provides a new means of visualizing surface anatomic structures of the fetus in utero. Our results suggest that three-dimensional ultrasonography has the potential to be a supplement to two-dimensional ultrasonography and should be useful in evaluating fetal abnormalities in high-risk pregnancies.

Embryonic and Fetal Development↗
PubMed1998

Mechanical strength of calcium phosphate cement in vivo and in vitro.

Two different kinds of calcium phosphate cement were developed for implant fixation: cement A comprised of alpha-tricalcium phosphate (alpha-TCP) 95% and dicalcium phosphate dihydrate (DCPD) 5%, and cement B comprised of alpha-tricalcium phosphate 90% and dicalcium phosphate dihydrate 10%. The compression strength and pullout force of the new materials were tested both in vitro and in vivo. Microscopic observations were performed on the interface between bone and cement. Cement A showed a greater mechanical strength than cement B. The results suggest the clinical possibility of this calcium phosphate cement, which could be used as a material for enhancing implant fixation.

Animals↗
PubMed1998

Increased serum levels of advanced glycation end-products and diabetic complications.

We determined serum advanced glycation end-products (AGE) levels in patients with NIDDM and evaluated the relationship between these levels and diabetic complications. The subjects consisted of 125 patients (mean age, 59.2 +/- 11.1 years, duration of diabetes 11.6 +/- 8.9 years, mean HbA1c, 6.8 +/- 1.0%) with stable blood sugar control. Sixty-three healthy volunteers (mean age, 58.3 +/- 12.7 years) served as controls. Serum AGE were measured by a newly developed ELISA method. Serum AGE levels were significantly higher in the diabetic group compared with the normal control group (7.2 +/- 14.6 vs. 3.3 +/- 1.0 mU/ml, P < 0.05). Significant correlations were seen between serum AGE and the degree of diabetic nephropathy. Serum AGE levels of diabetic patients with proliferative retinopathy were significantly higher than those of patients without proliferative retinopathy (5.7 +/- 1.8 vs. 3.1 +/- 1.0 mU/ml, P < 0.025) in the patient groups whose serum creatinine levels were between 2.0 and 3.9 mg/dl, although serum creatinine levels of both groups were not significantly different. Serum AGE levels reflected the severity of diabetic complications, including nephropathy and retinopathy.

Aged↗
PubMed1998

Novel antiallergic agents. Part I: Synthesis and pharmacology of pyrimidine amide derivatives.

We have synthesized many pyrimidine amide derivatives. Novel pyrimidine bis-glycolic amide derivatives showed moderate inhibition in the rat passive cutaneous anaphylaxis (PCA) assay by oral administration. Among these compounds, 2,4-bis(methoxyacetylamino)-6-piperidinopyrimidine (2i) exhibited significant inhibition. However the compound (2i) did not inhibit antigen-induced histamine or SRS-A release from lung fragments of the guinea-pig at less than 10(-4) M. Derivatives of 2i have also notable or moderate activity in the rat PCA assay. Compound 2h which has no oxygen atom at the alpha-position of the amide carbonyl group and, compound 17 which has no amide carbonyl group, showed no inhibition in the rat PCA assay. We supposed that both the amide carbonyl group and the oxygen atom at alpha-position of the amide carbonyl group play an important role in inhibiting the rat PCA reaction. These pyrimidine bis-glycolic amide derivatives have a novel structure and unique activity which suggests they may be potentially useful in the treatment of allergic diseases.

Administration, Oral↗
PubMed1998

Dynamics of the carbohydrate chains attached to the Fc portion of immunoglobulin G as studied by NMR spectroscopy assisted by selective 13C labeling of the glycans.

A systematic method for 13C labeling of the glycan of immunoglobulin G for NMR study has been developed. A mouse immunoglobulin of subclass IgG2b has been used for the experiment. On the basis of chemical shift and linewidth data, it has been concluded that (1) the mobility of the carbohydrate chain in IgG2b is comparable to that of the backbone polypeptide chain with the exception of the galactose residue at the nonreducing end of the Man alpha 1-3 branch, which is extremely mobile and (2) agalactosylation does not induce any significant change in the mobility. The results obtained indicate that even in the agalactosyl from the glycans are buried in the protein. Biological significance of the NMR results obtained is also briefly discussed.

Animals↗
PubMed1998

Somatic alterations of the SMAD-2 gene in human colorectal cancers.

The SMAD-2 gene, which is located at 18q21, has been identified as a candidate tumour-suppressor gene from work on colorectal cancers. The aim of the present study was to determine the clinical alterations and the significance of its mutations in a series of colorectal cancers previously examined for SMAD-4/DPC-4 gene. Mutation analyses of the SMAD-2 gene were carried out on cDNA samples from 36 primary colorectal cancer specimens using a combination of the polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP) and DNA sequencing. Only one missense mutation (2.8%), producing an amino acid substitution in the highly conserved region, and two homozygous deletions (5.5%) of the total coding region of the SMAD-2 gene were detected in the 36 cancers. The SMAD-2 gene may play a role as a candidate tumour-suppressor gene in a small fraction of colorectal cancers. However, allelic loss at 18q21 is very often seen in this type of tumour. Even in combination with changes in SMAD-4, the observed frequency was not sufficient to account for all 18q21 deletions in colorectal cancers. Thus, another tumour-suppressor gene, such as DCC, discovered as the first tumour-suppressor candidate in the region may also exist in this chromosome region.

Aged↗
PubMed1998

Delusions and hallucinations in patients with borderline personality disorder.

To clarify the nature of delusional and hallucinatory symptoms in borderline personality disorder (BPD), the authors investigated five patients with BPD who developed those symptoms, and discussed their duration, recurrence, types of variants and relation to the situation. The duration of these symptoms tended to vary widely, although six of 11 episodes lasted more than 7 days. Episodes tended to recur in all patients two or three times. Each episode could be classified into three types of delusions and hallucinations, such as delusions without hallucinations, complicated delusion and hallucination, and hallucinations without delusion. Delusions without hallucination occurred a total of four times in two patients and had a tendency to occur when the patient confronted personal adversities. They projected their feelings directly toward the person concerned. A complicated delusion and hallucination was observed three times in two patients. This type of symptom also tended to occur at the time of interpersonal problems but the patient's attitude was more passive. Hallucination without delusion occurred a total of four times in three patients. This symptom tended to occur when the patient avoided an interpersonal relationship. In this case the patients isolated themselves from others and withdrew.

Adolescent↗
PubMed1998

Three-dimensional ultrasonographic assessment of fetal hands and feet.

OBJECTIVE: The aim of this study was to describe fetal hands and feet using three-dimensional ultrasonography. DESIGN: This was a randomized prospective study. METHODS: Ninety-seven fetuses from 12 to 40 weeks' gestation were studied with a specially developed trans-abdominal three-dimensional transducer (3.5 MHz). The imaging system used in this study can provide conventional two-dimensional ultrasound images and can also generate, within seconds, high-quality three-dimensional images in the surface and transparent modes with no need for an external workstation. The rate of visualization of the hands/fingers and feet/toes at each gestational-age interval was calculated using two-dimensional and three-dimensional ultrasonography. RESULTS: The ability to visualize fetal hands/fingers and feet/toes was better with three-dimensional than with two-dimensional ultrasonography in the late first trimester (detection rates were 65% and 41% by three-dimensional ultrasonography for hands and feet, respectively, and 41% and 12%, respectively, by two-dimensional ultrasonography). For the early second trimester, detection rates were 82% for hands and 72% for feet by three-dimensional ultrasonography, and 54% for hands and 45% for feet by two-dimensional ultrasonography. Optimal visualization of the fetal fingers using three-dimensional ultrasonography was achieved between 28 and 35 weeks of gestation, although at this stage there were no significant differences in detection rates for hands and feet between two- and three-dimensional imaging. During this period it was possible with three-dimensional ultrasonography adequately to depict at least one hand in 93% of the fetuses at 28-31 weeks and in 88% at 32-35 weeks. The percentage of visualization of at least one fetal foot between 16 and 35 weeks using three-dimensional ultrasonography ranged from 50 to 85%. Before 15 weeks or after 36 weeks, the respective percentages decreased. CONCLUSIONS: Three-dimensional ultrasonography provides a novel means of visualizing fetal fingers and toes. Our observations suggest that three-dimensional ultrasonography may enhance the diagnostic potential of two-dimensional ultrasonography and might be useful in identifying fetal malformations and anatomical markers of chromosomal abnormalities prenatally in high-risk pregnancies.

Embryonic and Fetal Development↗
PubMed1998

Decreased maternal circulating hepatocyte growth factor (HGF) concentrations in pregnancies with small for gestational age infants.

Our purpose was to evaluate whether maternal and fetal hepatocyte growth factor (HGF) concentrations in pregnancies with small for gestational age (SGA) infants are different from those in pregnancies with appropriate for gestational age (AGA) infants. Maternal and fetal circulating HGF concentrations were compared between 55 pregnancies with AGA infants and 16 pregnancies with SGA infants at birth. HGF concentrations were measured from maternal and cord venous blood samples using an enzyme-linked immunosorbent assay. Umbilical artery blood pH and oxidative pressure (PO2) were also measured. Maternal circulating HGF concentrations (0.60+/-0.35 ng/ml) in pregnancies with SGA infants were significantly lower than those (0.91+/-0.44 ng/ml) in pregnancies with AGA infants (P = 0.012). There were no significant differences in fetal circulating HGF concentrations between both groups. No significant differences in umbilical artery blood pH and PO2 were found between both groups. These results suggest that the maternal serum circulating HGF concentration has a significant role in fetal growth during pregnancy.

Adult↗