Biomedical subjects

J Aoki

Publications and source records attributed to J Aoki.

At least 127 records · Page 7Linked to original sources

PubMed1996

PAF and PAF acetylhydrolase in the nervous system.

PAF acetylhydrolase is a key enzyme of PAF inactivation. Intracellular PAF acetylhydrolase isoform Ib is a heterotrimeric enzyme composed of alpha-, beta- and gamma-subunits. The beta- and gamma-subunits act as a catalytic unit and their amino acid sequences are homologous. The alpha-subunit is not essential for catalytic activity but is a product of the causative gene for Miller-Dicker lissencephaly, suggesting this subunit plays an important role in brain development.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1996

Force development of dynamic and static contractions in children and adults.

There are still unclarified points remaining in regard to the characteristics of force development in children who are immature in their basic activities in daily living. Moreover, there are morphological, histological, and biochemical differences between immature and mature muscles. In the present study, dynamic elbow flexion and static contractions which were performed by elbow flexors with maximum effort were examined by force-velocity and force-time relationships and electromyograms (EMG) in six-year-old children and in adults. In dynamic contractions with various loads, the force-velocity relationship for children was (P + 5.65) (v + 1.48) = 19.51, and (P + 14.65) (v + 2.26) = 96.21 for adults. The maximum power in children and adults was 22.8 watts and 160.8 watts, respectively. The contraction delay in children was greater than that in adults for every relative load. In static contractions, the maximum rate of force development for children was significantly lower than that for adults at each pre-tension. With an increase in pre-tension, the adult rate showed a tendency to decrease, whereas the rate for children showed no change. The electromechanical delay observed in children was significantly greater than that in adults. For dynamic and static contractions, the contractile speed in children was lower than that in adults.

Adult↗

PubMed1996

Hyaline cartilage: in vivo and in vitro assessment with magnetization transfer imaging.

PURPOSE: To elucidate the magnetization transfer (MT) effects of major components of hyaline cartilage. MATERIALS AND METHODS: The authors evaluated the MT effect of type II collagen and chondroitin sulfate phantoms (concentrations of 0.6%, 1.2%, 2.4%, 4.8%, 9.6%, and 19.2%), mass-cultured rat osteosarcoma-derived cells, and normal articular cartilage of the knee. RESULTS: The MT effect of collagen yielded a decrease in signal intensity of 10% (1.2% collagen) to 31% (19.2% collagen); the decrease varied linearly with collagen concentration. Chondroitin sulfate did not have a statistically significant MT effect. Cell pellets showed a decrease in signal intensity of 22%-26%, which was greater than that of 4.8% collagen. Normal articular cartilage of the knees showed a decrease in signal intensity of 38%-48%. CONCLUSION: The major role of collagen in MT contrast of hyaline cartilage was confirmed. In addition, a higher cellular contribution to the MT effect was also demonstrated.

Adolescent↗

PubMed1996

Stress fractures.

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Fractures, Stress↗

PubMed1996

MR findings indicative of hemosiderin in giant-cell tumor of bone: frequency, cause, and diagnostic significance.

OBJECTIVE: We studied the frequency, cause, and diagnostic significance of MR findings indicative of large amounts of hemosiderin in giant-cell tumor of bone. MATERIALS AND METHODS: The clinical, MR, and histologic findings in 16 patients with giant-cell tumors of bone were reviewed. Eight tumors occurred in uncommon locations or in patients who were not in the usual age range; the other eight were more typical. Areas of decreased MR signal intensity considered to be caused by hemosiderin were identified. The number and distribution of RBCs within the tumor were studied histologically, and the presence of hemosiderin was determined on histologic sections made with iron stains. RESULTS: In 10 cases in which MR images showed areas of low signal intensity, large amounts of hemosiderin were noted histologically. The low-signal-intensity areas were nodular, zonal, whorled, or diffuse and occupied at least one fifth of the tumor volume. On histologic examination, many erythrocytes were in direct contact with the tumor cells, and the hemosiderin was seen in both mononuclear and multinuclear tumor cells. CONCLUSION: Hemosiderin is commonly seen on MR images of giant-cell tumors of bone (63%) and is probably related to the extravasated erythrocytes in the tumor and the phagocytic function of the tumor cells. This MR finding supports the diagnosis, even in giant-cell tumors in uncommon locations or in patients who are not in the typical age range.

Adult↗

PubMed1996

[Evaluation of image quality of medical facsimile as a radiological image recording system].

We examined the usefulness of a new medical facsimile (MFAX) system in recording and transmitting various kinds of medical images, including X-ray images and colored histopathologic images. The system consists of an image scanner, a magnetic disk for image storage, a transmission circuit and a thermal image printer. Transmission time for a FCR (Fuji computed radiography) image by super-fine mode was 6 minutes. We used ROC (receiver operating characteristics) curves to evaluate the ability of eight radiologists to detect the small simulated nodules placed on an anthropomorphic chest phantom and shown on MFAX images. The radiologists observed both the FCR films and MFAX copies and determined the presence or absence of simulated nodules using five confidence levels. The results obtained for FCR films and MFAX images showed no statistically significant difference.

Humans↗

PubMed1996

[Effect of collagen on magnetization transfer contrast assessed in cultured cartilage].

We investigated the effect of collagen on magnetization transfer contrast (MTC) in cultured cartilage. In our culture system, only collagen synthesis was increased by the addition of vitamin C, while proteoglycan synthesis and the number of chondrocytes were unaffected. The MTC effect was assessed by using an off-resonance RF pulse (0.3 KHz off-resonance, sinc wave of 18 msec, maximum amplitude 4.61 x 10(-4)T) on a GRASS sequence. The cartilage cultured with vitamin C showed a higher MTC effect than that cultured without vitamin C. The major role of collagen on MTC was confirmed in living cartilage tissue.

Animals↗

PubMed1995

Cloning and expression of a cDNA encoding the beta-subunit (30-kDa subunit) of bovine brain platelet-activating factor acetylhydrolase.

Bovine brain platelet-activating factor (PAF) acetylhydrolase isoform Ib is a heterotrimeric enzyme. Its gamma-subunit (which, formerly, we called the 29-kDa subunit) acts as a catalytic subunit, whereas the alpha-subunit (45 kDa) is the bovine homolog of the product of human LIS-1, the causative gene of Miller-Dieker lissencephaly, indicating that this intracellular PAF acetylhydrolase plays a key role in brain development. In the current study, we cloned the cDNA for the beta-subunit (30 kDa) of bovine brain PAF acetylhydrolase Ib. The predicted 229-amino acid sequence was homologous (63.2% identity) to that of the gamma-subunit, especially (86% identity) in the catalytic and PAF receptor homologous domains. The recombinant beta-protein produced in Escherichia coli showed significant PAF acetylhydrolase activity. A mutant protein, in which Ser48, which corresponds to the active serine residue of the gamma-subunit, was replaced with cysteine showed no enzymatic activity, suggesting Ser48 is the active serine residue. Although the beta- and gamma-subunits form a heterocomplex in the native enzyme, both recombinant beta- and gamma-proteins exist as a homodimer. The purified recombinant beta-protein was labeled readily with [1,3-H]diisopropyl fluorophosphate, whereas the beta-subunit in the native complex was only labeled with higher concentrations of [1,3-3H]diisopropyl fluorophosphate to a lesser extent than the gamma-subunit. Combined with our previous data, the present study demonstrated that bovine brain PAF acetylhydrolase Ib is a unique enzyme possessing two catalytic subunits and another, possibly regulatory, subunit.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1995

[Clinical application of digital TV tomosynthesis to disorders of the wrist and their post-operative evaluation].

The clinical utility of digital TV tomosynthesis was assessed in 13 patients with chronic disorders of the wrist and the first carpometacarpal joints, and a post-operative evaluation was carried out. The disorders included nonunion of the scaphoid in five patients, Kienböck's disease in four, subluxation of the distal radioulnar joint in two, and osteoarthrosis of the first carpometacarpal joint in two. The total time needed to obtain two sets of tomographs of a wrist by digital TV tomosynthesis was about 10 minutes, or approximately one third of the time required with conventional methods. The total radiation exposure in obtaining all tomographs of one direction with digital TV tomosynthesis was less than that in obtaining only one tomograph with conventional methods. Digital TV tomosynthetic images were judged superior to conventional tomographs by four orthopedic surgeons and four radiologists, because tomographic blur was reduced in part by a spatial frequency filter processing. Clinically, digital TV tomosynthesis was very helpful in evaluating nonunion of the scaphoid and Kienböck's disease, especially in their post-operative conditions with metallic fixative devices. Digital TV tomosynthesis was found to be a fast, feasible and inexpensive method with low radiation exposure for evaluating disorders of the wrist.

Adult↗

PubMed1995

[Radiological and anatomical investigation of calcific tendinitis of the gluteus maximus tendon].

The radiological findings in four cases of gluteus maximus tendinitis were retrospectively analyzed. All the patients underwent radiographic, CT and MRI examinations. Amorphous or round calcifications were detected on lateral radiographs in three cases, and on CT in all cases. A small cortical erosion was observed in three cases on both radiographs and CT. MRI showed a thickened gluteus maximus tendon, but no other specific features. In the supine position, which is common in routine CT and MRI studies, the calcific deposits appeared to be distributed along the vastus lateralis muscle tendon. To correlate these radiographic observations with the topographic anatomy of the tendon's insertion, we investigated 14 thighs of seven cadavers, and clarified that the tendon's insertion was the main component of the lateral femoral intermuscular septum. Consequently we performed MRI on a volunteer in a prone position who was asked to maintain contraction of the gluteus maximus and quadratus femoris muscles. The images obtained showed clearly that the gluteus maximus tendon was directed dorsally. In conclusion, radiography and CT are the modalities of choice for diagnosis of this entity. Additionally, radiologists should be aware that the gluteus maximus tendons are directed laterally as a main part of the lateral femoral intermuscular septum on routine CT and MRI.

Buttocks↗

PubMed1995

[Trial of a small image network system in a radiology department of an university hospital].

This paper describes the construction of an image network system in Shinshu University Hospital, and some of its current issues and advantages. Our discussion is based on our experience with a PACS system. SAIPACS, which was installed in 1990 for use in clinical conferencing and pre- and post-graduate education, and with a new CT and MRI network, which was subsequently introduced in 1993. The SAIPACS interconnects eight digital imaging modalities, including CT, MRI, XTV-DR (including digital tomosynthesis), FCR, nuclear medicine (RI), DSA, US, and a film digitizer (FD), with a workstation. Transmission time from the magnetic disk of each imaging modality to the SAIPACS image disk is not rapid enough. Therefore, we need to select images for transfer that are pertinent to our specific purpose, to complete image transmission within a practically acceptable period of time. The new CT/MRI network is composed of two CT units, two MRI systems, an image processing unit and a Universal Gateway. It provides faster image transmission than the SAIPACS system, because there is no need to reform image data to send them in a reversible compressed form. A versatile network system connected to the SAIPACS and CT/MRI network enables digital image data to be processed and edited and images to be transferred back to SAIPACS for clinical or educational use.

Computer Communication Networks↗

PubMed1995

[High-resolution teleradiology system based on ISDN and small computer].

A high-speed, high-resolution teleradiology system based on the Integrated Services Digital Network (ISDN) is described. The LAN at Saku Central Hospital and the Radiological Department at Shinshu University Hospital (60 km) are interfaced to a Macintosh computer with an image digitizer, interactive display, and network interface. The transmission time for a digitized high-resolution radiographic image with 4.39 megabytes was 358 seconds using a 128 kbps (kilobit-per-second) channel (B1 + B2), and the mean transmission rate was 98.1 kbps. Teleradiology conference is also available using this system. Radiologists can observe the same high-resolution images on the CRT screen simultaneously at two different remote hospitals, indicating a point of interest on the image by means of a mouse cursor. Graphical data of interest to the radiologists are also transmitted and displayed on the CRT.

Computer Communication Networks↗

PubMed1995

[Between "play" and "playing"--exploring the identifying base of play].

Up to the present, the majority of theories regarding play were grounded on the perspective of the observer rather than the perspective of the person engaged in play. When viewing the figure of someone playing, however, no one can draw the conclusion that the person "is playing". This is because play can be identified solely by the awareness of the player absorbed in play. Nevertheless, this awareness varies infinitely according to the individual. Moreover, when the player is absorbed in play but is not conscious that s/he is playing, strictly speaking, the activity cannot defined as play. To identify play, we regard both the player's playing awareness itself and the self-awareness of being engaged in play as indispensable elements. Furthermore, these two forms of awareness should be discussed, not by enclosing them within the player's individual mind, but from the standpoint of a relationship of mutual compensation through continuous interchange between the player and others. The theory of play can approach the real image of play only by extracting the modality of these forms of awareness.

Child↗

PubMed1994

[High-speed/high resolution teleradiology system based on university microwave network].

A high-speed, high-resolution teleradiology system with full duplexing based on the Shinshu University Video and Communication Network System (SUNS) using Giga-Herz microwaves is described. The LAN at Nagano Red-Cross Hospital and The Radiology Department of Shinshu University Hospital are interfaced to a personal computer with a laser film digitizer, interactive display, and network interface. The throughput per digitized high-resolution radiographic image was 65 sec, and the mean transmission rate was 805 kilobit per sec. Teleradiology conferencing is also possible with this system. Radiologists at both hospitals interactively observe the same high-resolution images on the CRT screen using mouse cursor synchronization.

Computer Communication Networks↗

PubMed1994

Amino acid residues on human poliovirus receptor involved in interaction with poliovirus.

We have previously demonstrated that the N-terminal immunoglobulin-like domain (domain 1; 115 amino acids) of human poliovirus receptor (hPVR) is essential for poliovirus binding and infection to cells. To identify amino acids involved in the interaction with poliovirus, we constructed a number of cDNAs encoding mutant hPVRs whose domain 1 was partially derived from mouse PVR (mPVR) homolog, which does not serve as a binding site for poliovirus. Poliovirus binding and infection assays were performed on mouse L cells that express these chimera cDNAs. Anti-hPVR monoclonal antibodies were employed to confirm the presence of mutant PVRs on the surface of mouse cells and to know conformational alteration of these PVRs. A significant decrease in efficiency of both poliovirus binding and infection to the cells was observed when one or a few amino acids of hPVR at Gly73, Ser74, Gln82, Leu99-Glu102, or Gln130-Ser132 were substituted by the corresponding amino acids of mPVR. Similar results were obtained when a 2-amino acid insertion of mPVR, which was missing in hPVR, was introduced at the corresponding site (between Arg98 and Leu99) of hPVR. These amino acids were highly conserved in functional PVRs of primates but not in unfunctional PVRs of rodents. These results indicate that the amino acids identified may have important roles in interaction of PVR with poliovirus that leads to the establishment of the virus infection. In the three-dimensional model of the domain 1 of hPVR, these amino acids are located on one side of the molecule. This suggests that the interaction with poliovirus occurs on this side of the domain 1.

Amino Acid Sequence↗

PubMed1994

Anti-idiotypic monoclonal antibody recognizes a consensus recognition site for phosphatidylserine in phosphatidylserine-specific monoclonal antibody and protein kinase C.

In order to elucidate the molecular mechanisms responsible for the specific lipid-protein interactions, we have undertaken structural and idiotypic analyses of a monoclonal antibody, PS4A7, which binds specifically to phosphatidylserine (PS). Here we showed that one of the anti-idiotypic monoclonal antibodies raised against PS4A7 cross-reacted extensively with protein kinase C (PKC) and inhibited the activation of the enzymatic activity. The binding of the anti-idiotypic antibody to PKC was inhibited specifically by PS, but not by other phospholipids including 1,2-diacyl-sn-glycero-3-phospho-D-serine or 1,2-diacyl-sn-glycero-3-phospho-L-homoserine. In contrast, the binding of the anti-idiotypic mAb to the enzyme was significantly enhanced in the presence of either diacylglycerol or sphingosine. These findings indicate that the PS-specific monoclonal antibody and PKC share a consensus structure which is responsible for the specific interaction with PS and both diacylglycerol and sphingosine may induce a similar conformational change which exposes the PS-specific binding site of the enzyme.

Amino Acid Sequence↗

PubMed1994

Characterization of three different transgenic mouse lines that carry human poliovirus receptor gene--influence of the transgene expression on pathogenesis.

Three transgenic mouse lines, ICR-PVRTg1, ICR-PVRTg5, and ICR-PVRTg21, which are susceptible to poliovirus, have been established by introducing the human gene for poliovirus receptor (PVR) into the genome of mouse strain ICR. Genetic characterizations of the PVR gene were carried out on these mouse lines to define the approximate copy number, insertion site, and expression of the transgene in the central nervous system (CNS). The transgene was integrated in the chromosome 4, 12, and 13 of ICR-PVRTg1, ICR-PVRTg5 and ICR-PVRTg21 mice, respectively, and was stably transmitted to progeny mice. ICR-PVRTg1 appeared to have the most abundant copy numbers of the transgene and showed the highest level of PVR mRNA and membrane associated PVR protein in the CNS among the three mouse lines. Those in ICR-PVRTg21 and ICR-PVRTg5 were at intermediate and lowest levels, respectively. In the CNS, PVR mRNA was detected at high levels only in neurons of the spinal cord and brain stem where poliovirus can replicate, suggesting that the PVR mRNA expression confers cell specificity to poliovirus in the CNS. ICR-PVRTg1 and ICR-PVRTg5 showed the highest and the lowest sensitivity to poliovirus, respectively, whereas ICR-PVRTg21 was in-between. These results may suggest that poliovirus sensitivity of the mice is attributed to relative levels of PVR expression.

Animals↗

PubMed1994

Giant neurinoma occupying the holocervical and upper thoracic regions: case report.

We report a case with a giant spinal neurinoma located between the foramen magnum and fifth thoracic levels. The patient did not develop any neurologic symptoms until 16 years after the onset of hydrocephalus. The latter, successfully treated with a ventriculoperitoneal shunt, was associated with a cerebrospinal fluid protein of 400 mg/dL and was in all probability the first sign of the spinal cord tumor.

Aged↗