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Biomedical subjects

K Hayamizu

Publications and source records attributed to K Hayamizu.

At least 37 records · Page 2Linked to original sources
PubMed1998

A model for diffusive transport through a spherical interface probed by pulsed-field gradient NMR.

In biological systems, because of higher intracellular viscosity and/or the restriction of the diffusion space inside cells, the (apparent) diffusion coefficient of an intracellular species (e.g., water) is generally smaller than when it is in the extracellular medium. This difference affects the spin-echo signal attenuation in the pulsed field gradient NMR experiment and thus affords a means of separating the intracellular from the extracellular species, thereby providing a basis for studying transmembrane transport. Such experiments have commonly been analyzed using the macroscopic model of Kärger (see Adv. Magn. Reson. 21:1-89 (1988)). In our previous study, we considered a microscopic model of diffusive transport through a spherical interface using the short gradient pulse approximation (J. Magn. Reson. A114:39-46 (1995)). The spins in the external medium were modeled with the "partially absorbing wall" condition or as having a small but finite lifetime. In the present paper, we extend our treatment to the case in which there is no limitation upon the lifetime in either medium. We also consider a simple modification of Kärger's model that more properly accounts for the restricted intracellular diffusion. Importantly, it was found that the exact solution within the short gradient pulse approximation developed here and the modified Kärger model are in close agreement in the (experimentally relevant) long-time limit. The results of this study show that when there is no limitation upon the lifetime of the transported species in either phase, the spin-echo attenuation curve is very sensitive to transport.

Diffusion↗
PubMed1997

Optimization of the water-PRESS pulse sequence and its integration into pulse sequences for studying biological macromolecules.

In this paper, the recently developed "Water-PRESS" method of water suppression [W. .S. Price and Y. Arata (1996), J. Magn. Reson. B 112, 190] in which homospoil pulses are used to manipulate the effects of radiation damping on the water resonance and thereby selectively alter the effective relaxation times of the water resonance with respect to the solute (e.g., biological macromolecules) resonances is further developed and applied. In the present work, methods for optimization in terms of degree of water suppression and in temporal terms (important for the application of Water-PRESS to multidimensional experiments) are considered so that recycle delays of less than 2.3 s (including the acquisition time) are possible. Also, a simple modification which allows the observation of solute resonances with relaxation times similar to that of the water resonance is presented. Finally, the inclusion into more complicated pulse sequences is also discussed. Experimental examples using aqueous samples of lysozyme and immunoglobulin are given. Compared to most other NMR water suppression techniques, this method is extremely simple to implement and optimize and does not require accurately calibrated RF pulses or perfect lineshape.

Animals↗
PubMed1996

Mechanisms of tolerance to rat heart allografts using posttransplant TLI. Changes in cytokine expression.

Lewis rats were rendered tolerant to ACI heart allografts using a regimen of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte or antilymphocyte globulin (RATG or RALG), and a single donor blood transfusion. All three treatment modalities were required to induce tolerance. The mechanism of the maintenance of tolerance was investigated by comparing the secretion of cytokines in the MLR, and the expression of cytokine mRNA in the allografts of tolerant and nontolerant Lewis rats. Although, the 3H-thymidine incorporation and secretion of IL-2 was frequently comparable in the MLR from tolerant and nontolerant rats, the secretion of IFN-gamma was markedly reduced in the tolerant rats. This was reflected in a markedly reduced frequency of cells expressing IFN-gamma mRNA in the allografts of tolerant as compared with nontolerant hosts. The frequency of cells expressing IL-2 and IL-10 mRNA was also reduced, but no significant difference was observed for cells with IL-4 mRNA. Spleen cells from nontolerant rats rapidly rejected ACI allografts in irradiated adoptive hosts, but spleen cells from tolerant rats did not. Evaluation of the cytokine mRNA expression at early and late time points in the allografts of adoptive hosts showed a pattern similar to that of the primary hosts. Thus, the tolerant state was associated with a maintenance or elevation of IL-4 expression and a marked reduction of IFN-gamma expression. Previous reports have shown that TLI alone induced this shift in the early recovery phase after irradiation.

Animals↗
PubMed1995

[Ultrasonography for traction injuries of the brachial plexus].

Results of preoperative ultrasonography (US) were compared with the subsequently offered operative findings retrospectively on 35 ventral rami of the cervical nerves (11 C5, 11 C6 and 13 C7) in 12 patients injured in motorcycle accidents in order to examine the usefulness of US in the diagnosis of nerve injury. The findings of a US-scanned ramus consisted of shape, internal echo pattern, regularity of border, and ratio of the diameter of an injured nerve to that of the corresponding nerve on the intact side (I/C). An intact ventral ramus was shown as a hypoechoic tubular structure with many parallel fine linear internal echoes, a regular border, and I/C ranging from 1.0 to 1.2. Categories such as I/C and shape improved the accuracy of differential diagnosis of severe nerve injuries. Avulsion of the ganglion was observed as a winding or tadpole-shaped remarkably enlarged (2.3 < or = I/C < or = 5.0) mass lesion, intraforaminal lesion as a thick (1.5 < or = I/C < or = 3.2) structure with an irregular shape and border close to the transverse process, and pseudocontinuity as irregular internal echoes. It was difficult to discriminate a lesion with continuity and localized scar formation around the nerve from normal fasciculi. These results strongly suggest that the application of improved US diagnosis to cervical nerve injury should make it much easier to select the best treatment for the patient, in that we can detect preoperatively those injuries to which nerve transplantation is not applicable.

Adolescent↗
PubMed1994

[Ultrasonography in the joints of hands with rheumatoid arthritis].

The findings of preoperative ultrasonography (US) in 37 joints of 12 patients with rheumatoid arthritis (RA) were evaluated and compared with clinical staging and operative findings. By US, synovial proliferation in the joints was observed as hypoechoic solid tumor. By dynamic examination of the metacarpophalangeal (MP) joints, the developmental process of joint immobilization could be detected through a close study of the relationship between the proliferated synovium and extensor tendons, synovial bursa, sagittal bands, and expansion hoods. As the cartilage and heads of the metacarpal bones and proximal phalanges could be demonstrated by dorsal scanning of the articular space of the over-flexed MP and proximal interphalangeal (PIP) joints, small synovial proliferation and irregular border of the cartilage could be detected during the early stage of inflammation. The findings of the present study showed that the application of preoperative US to RA patients was very useful for early diagnosis and for the selection of treatment, including operative methods.

Adult↗
PubMed1994

[Preoperative evaluation of tendons in the hands of patients with rheumatoid arthritis by ultrasonography].

The findings of ultrasonography (US) of 52 tendons of the hands of 14 patients with chronic rheumatoid arthritis (RA) were compared with operative findings obtained subsequently. US showed tenosynovitis as expansion of a hypoechoic area around the tendon. US also enabled pattern classification based on shape, internal echo and border features of the scanned tendon, differentiation of acute and progressive stages among acute inflammation, invasion of tenosynovitis, degeneration, and rupture of the tendon to be made, and the progression of tendon lesions could be ascertained. It was found that in inflammation the tendon was significantly thickened, and in degeneration, the tendon was thinned. By dynamic US scanning, disturbances of tendon movement due to tendon rupture and adhesion to surrounding structures could be detected and differentiated. It was found in this study that preoperative US of the hand of RA patients is very useful for early diagnosis and for the selection of treatment including operative methods.

Adult↗
PubMed1994

[Ultrasonographic evaluation of joints and tendons in the normal hand].

Ultrasonography (US) using high frequency probes (7.5 and 10MHz) was applied to the anatomical observation of joints and tendons of the hands of 12 normal volunteers, and in some cases comparison with MR imaging and detection by double-contrast arthrography of internal joint structure was made. Dorsal scanning of the metacarpophalangeal joint (MPJ) and proximal interphalangeal joint in the flexed position clearly demonstrated the cartilage and bone heads of the metacarpal and proximal phalange. By US, the structure of such connective tissues as synovial bursa, sagittal band, expansion hood, volar plate and fibrous digital sheath around the MPJ could be identified. By dorsal scanning in the long axis between the ulnar and carpal bone, a part of the triangular fibrous cartilage could be observed. Long and short axis scans of the hand demonstrated the flexor and extensor tendons as having a fibrillar texture with high echogenicity. In dynamic examinations including color Doppler imaging, the movability of the tendons could be evaluated. The result of the present study indicated that US can be effectively applied for diagnostic imaging of the joints, structures surrounding the joints, and tendons of the hand.

Adult↗
PubMed1994

Mechanism of suppression of cloned human suppressor T cells.

We report the mechanism of suppression of suppressor T cell clone III-1-C5 using helper T cell clone III-1-B6, mitogen responses and rIL-2. Clone III-1-C5 suppressed the mixed lymphocyte reaction (MLR) by secreting alloantigen non-specific, MHC non-restricted suppressor factor(s). Clone III-1-C5 did not suppress mitogen (PHA, Con A, PWM) response nor proliferation by exogeneous rIL-2. Clone III-1-C5 suppressed proliferation by clone III-1-B6, which augments proliferation by direct cell to cell contact with responder cells and not by soluble factors. These results indicated that suppressor T cells exhibit suppressive effects not only by inhibiting IL-2 synthesis but by inhibiting the direct effects of helper T-cells.

Animals↗
PubMed1994

Inhibition of IL-2 synthesis by donor-specific suppressor T cells in a renal transplant recipient.

A study was conducted to elucidate the mechanism of donor-specific Mixed Lymphocyte Reaction (MLR and Cell Mediated Lymphotoxicity (CML) unresponsiveness in a renal transplant recipient with a long-term well-functioning kidney. The peripheral blood lymphocytes (PBL) of the recipient, who had not shown rejection since his transplantation 5 years previously, and those of his mother (donor), his father and two healthy third parties were examined. MLR, CML, semimicro MLR in a double chamber, interleukin-2 (IL-2) synthesis assay and limiting dilution assay were performed. This recipient showed donor-specific MLR and CML unresponsiveness. IL-2 assay showed that the PBL of the recipient produced less IL-2 against the donor than against the father and the third parties. The addition of exogenous recombinant IL-2 (rIL-2; Takeda Co.) to the priming MLR caused a recovery of CML against the donor. A limiting dilution assay indicated that cytotoxic T cell precursor (CTLp) frequencies against the donor and father did not differ. The suppressor assay in a double chamber indicated that the PBL of the recipient stimulated by the donor PBL had a non-specific suppressive effect on MLR, CML and IL-2 synthesis of the PBL across the Major Histocompatibility Complex (MHC) barrier. This suppressive effect was abolished by OKT3 or OKT8 monoclonal antibody and complement. Thus, the recipient had donor-specific suppressor T cells that produced a humoral non-specific suppressive factor only when stimulated by the donor PBL, and this factor suppressed MLR and CML by inhibiting IL-2 synthesis of the PBL.

Antibodies, Monoclonal↗
PubMed1993

Induction of natural suppressor-like cells from human adult peripheral blood lymphocytes by a K562-derived factor.

K562-AC1, a subclone of the human myeloid leukemia cell line K562, secreted an inhibitor of PHA-stimulated human T cell growth into the culture supernatant (K562sup). Kinetics and absorption assays in vitro revealed that the factor acts on PBMC during the very early growth phase. PBMC gained potent suppressor activity against autologous T cell growth after preculture with K562sup for 3 days in a dose-related manner. HLA class II negative and nylon wool-nonadherent subsets possessed higher suppressor potential than unfractionated PBMC. Treatment of K562sup-precultured PBMC with mAb followed by complement-lysing showed that the responsible suppressors belong to null cells expressing CD3-, CD4-, CD19-, CD14-, CD11b-, but partially CD2+. Exogenous IL-2 exhibited a synergistic effect on the activity of the suppressors committed by K562sup. However, K562sup inhibited IL-2-activated lymphocytes from generating anti-K562 cytolytic activity. Macrophages inhibited the induction of the suppressors, which was restored by adding indomethacin and/or IL-2. In conclusion, K562sup has the ability to induce efficient suppressor cells from human adult PBL, which belong to null cells without NK/lymphocyte-activated killer activity and are similar to natural suppressor cells.

Humans↗
PubMed1992

Suppression of human lymphocyte proliferation and cytotoxic T lymphocyte generation by a soluble factor derived from K562 cells.

The human myeloid leukemia cell line, K562, secrets a lymphocyte growth-suppressive factor (LGSF). We report our investigation of the immunological and chemical features of this factor. LGSF showed no cytolytic effect on human peripheral blood mononuclear cells (PBMC). Nevertheless, LGSF adequately suppressed in vitro alloantigen- or mitogen (PHA, ConA, PWM)-stimulated human PBMC proliferation and alloantigen-induced cytotoxic T lymphocyte generation, in antigen-nonspecific and LGSF concentration-related manners. LGSF retained activity after filtration through a 0.22 microm filter membrane and storage at -80 degrees C for 6 months. Ultrafiltration experiments indicated that suppressive activity was retained in the higher molecular weight fraction (MW > 100,000) and that the activity was heat-labile at 56 degrees C for 30 min. These results strongly suggested that LGSF is a noncytotoxically immunosuppressive substance with a high molecular weight.

Humans↗
PubMed1991

[Evaluation of hepatic tumors by contrast ultrasonography with carbon dioxide].

For evaluating hepatic tumors, ultrasonograms using carbon dioxide by arterial injection (CO2US) was performed in 37 patients, including 28 hepatocellular carcinomas, 11 hepatic metastases, and 3 hepatic hemangiomas. Hepatic tumors were enhanced by CO2US and easily identified. CO2US of hepatic tumors were classified into six patients. Generally, on CO2US hepatocellular carcinomas were well enhanced, and hepatic metastases had ring-like enhancement. Hepatic hemangiomas showed peripheral patchy enhancement. In the patients with hepatocellular carcinoma, the primary tumors were better identified on CO2US than conventional sonography. The daughter nodules with hepatocellular carcinoma were also better demonstrated than other examinations. CO2US is helpful in evaluating and differentiating hepatic tumors.

Aged↗
PubMed1990

[Internal rotation angle measurement of the elbow with 3D reformatted CT image].

The examination of internal rotation angle at the elbow is difficult on conventional radiographs. The angle of internal rotation has been measured with three dimensional reformatted CT image of GE CT/T9800. The angle of internal rotation with the cubitus varus deformity was measured both preoperatively and postoperatively. Postoperatively the angle of internal rotation became equal on both sides. Three dimensional CT reconstruction is useful in determining the internal rotation angle of elbow.

Adult↗