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Biomedical subjects

H Yuasa

Publications and source records attributed to H Yuasa.

At least 253 records · Page 14Linked to original sources
PubMed1987

Studies of the slow releasing of testosterone from radiation-polymerized testicular prostheses implanted subcutaneously in the back of castrated rabbits.

A controlled release testicular prosthesis containing testosterone, which was previously dissolved in 2-hydroxyethyl methacrylate (HEMA) at a temperature of 80 degrees C, was prepared by radiation-induced polymerization in the supercooled state at a low temperature. The daily dose of testosterone released in vitro from the poly(HEMA) testicular prosthesis was kept constant at a rate of 5.5 +/- 1.5 mg/d throughout an experimental period of 900 d. In the in vivo experiments, the poly(HEMA) testicular prosthesis was implanted subcutaneously in the back of castrated rabbits over a maximum period of 11 mnth. The cumulative amounts of testosterone released in vitro and in vivo from the poly(HEMA) testicular prosthesis for a period of 11 mnth were found to be 2.1 g (30.0 wt% of initial drug) and 0.9 g (12.8 wt% of initial drug), respectively. The serum testosterone level in castrated rabbits with a poly(HEMA) testicular prosthesis rapidly decreased for periods up to 2 mnth (after increasing during the first 2 wk), then showed a moderate decrease for a few months, and finally held constant at a level of 10 ng/ml throughout the experimental period. It was concluded that a slight amount of testosterone is continuously released in vivo from the radiation-polymerized poly(HEMA) testicular prosthesis over a long period analogous with that in vitro.

Animals↗
PubMed1987

Variation in D-glucose uptake along the intestinal tract.

The variation in D-glucose uptake along the intestinal tract was examined by dividing the entire rat small intestine into 10 segments of equal length and by using everted sacs. The superiority of jejunum to ileum in D-glucose uptake, which is generally accepted, was supported by this work. It was attributed mainly to the variation in the maximal transport velocity of the Michaelis-Menten type carrier-mediated transport system with a clear kinetic border in the distal location of the small intestine, between segments 7 and 8. Information obtained in this study is useful for understanding and estimating the absorption process, or the time-course of absorption, of D-glucose as it passes down in the intestinal tract.

Animals↗
PubMed1986

Construction of rat-mouse T cell hybridomas that express regulatable rat interleukin 2 receptor.

Spleen cells obtained from Lewis rats were cultured with 4 micrograms/ml Con A for 96 hr, and activated cells were fused with BW5147 mouse T lymphoma cells. Seven clones obtained by fusion expressed rat IL 2R. The expression of rat IL 2R on those hybrid cells could be up-regulated by IL 2 itself, ATL-derived factor, and TPA and CA++ ionophore. Those IL 2R could be down-regulated by murine MoAb ART-18 that detects rat IL 2R. All hybrid clones produced IL 2 constitutively. IL 2 produced by hybrid cells bound to its receptor and promoted the proliferation of hybrid cells in some clones. Incubation of cells with exogenous IL 2 resulted in the proliferation of hybrid cells, whereas the proliferation of some clones was inhibited by exogenous IL 2, indicating that IL 2 had bifunctional properties on cell growth. Rat IL 2R from 6H2-F9 hybrid cells was studied by both one- and two-dimensional SDS-PAGE with ART-18. The IL 2R derived from 6H2-F9 cells had 72,000 to 77,000 and 40,000 to 48,000 m.w. major components under nonreducing conditions, and had 50,000 to 56,000 m.w. major and 35,000 to 38,000 m.w. minor components under reducing conditions. The 110,000 m.w. component, the third component of IL 2R, was constantly observed in 6H2-F9 hybrid cells.

Animals↗
PubMed1986

[Studies on estramustine-binding protein in the human prostate].

In the present study, size exclusion HPLC was used to analyse the properties of Estramustine-binding protein (EMBP) in the cytosol of human benign prostatic hypertrophy (BPH). The typical size exclusion HPLC separation profile of 3H-Estramustine-labelled cytosol of BPH showed four radioactive peaks that corresponded to the V0, 250K, 68K and 45K protein regions. The specific binding protein for Estramustine is contained mainly in the 250K protein region and in part in the V0 region. In the presence of sodium molybdate, the specific Estramustine binding to a 250K protein was increased to a level which was about 2.5 times as much as the value in the absence of sodium molybdate. The specific Estramustine binding to a 250K protein under the condition of no DCC treatment and the addition of sodium molybdate was 600% of the value obtained under the condition of DCC treatment and no addition of sodium molybdate. These results suggested that sodium molybdate stabilized the specific Estramustine-binding activity to a 250K protein and that specific Estramustine binding to a 250K protein seemed to be weaker than the binding of androgen to androgen receptor.

Carrier Proteins↗
PubMed1986

5C6-F4, a novel 100,000-dalton rat lymphocyte activation antigen defined by monoclonal antibody.

Con A-activated rat thymocytes were used to immunize mice, and immune spleen cells were fused with NS/1 myeloma cells. One clone, designated 5C6-F4, reacted strongly with Con A-activated rat thymocytes and some LPS-activated rat spleen cells but not with normal thymocytes, spleen cells, or bone marrow cells of rat origin. The 5C6-F4 did not react with Con A-activated thymocytes of mouse origin. Immunoprecipitation of 5C6-F4 antigen from surface-iodinated Con A-activated rat thymocytes or LPS-activated rat spleen cells revealed its m.w. to be approximately 100,000. The kinetic studies of the expression of 5C6-F4 antigen revealed that 5C6-F4 antigen was detectable at 6 hr after Con A stimulation of rat spleen cells, whereas IL 2 receptor (IL 2R) was detectable at 12 hr. The appearance of 5C6-F4 antigen and IL 2R precede the onset of DNA synthesis of Con A-activated spleen cells. Thus, 5C6-F4 antigen is classified as early activation antigen. The 5C6-F4 inhibits the lymphocyte proliferation induced by mitogen and the IL 2-driven rat T cell proliferation. Sequential immunoprecipitation study as well as binding inhibition study indicated that the 5C6-F4 antigen is distinct from IL 2R molecule. The 5C6-F4 antigen appears to be a novel rat lymphocyte activation antigen that exhibits immunoregulatory function and also may serve as a useful marker of T cell activation.

Animals↗
PubMed1986

Determination of kinetic parameters of a carrier-mediated transport in the perfused intestine by two-dimensional laminar flow model: effects of the unstirred water layer.

The kinetic parameters of a carrier-mediated transport for D-glucose and for taurocholate were determined from rat in situ intestinal single perfusion experiments. The true parameters were obtained by the two-dimensional laminar flow model, in which the solute concentration at the aqueous-intestinal membrane interface can be calculated numerically without assuming the aqueous diffusion layer, discriminating the effects of the unstirred water layer. The true Michaelis constant was 4.5 mM for D-glucose and 1.5 mM for taurocholate. The true maximal transport velocity was 3.4 nmol/s per cm2 for D-glucose and 0.29 nmol/s per cm2 for taurocholate. The apparent Michaelis constant was raised by the factor of 6.6 for D-glucose and 3.6 for taurocholate due to the effects of the unstirred water layer. The maximal transport velocity was relatively unaffected by the unstirred water layer in both compounds. The values of the effective (operational) thickness of the unstirred water layer were compatible with those reported previously by employing various experimental methods. The kinetic parameters obtained in vitro everted sacs, for comparison, almost coincided with the true ones in situ. Therefore, the two-dimensional laminar flow model is shown to be valid not only for determining the kinetic parameters of a carrier-mediated transport in situ but also for predicting the absorption rate in situ from the uptake rate in vitro.

Animals↗
PubMed1986

Intestinal absorption by carrier-mediated transports: two-dimensional laminar flow model.

The two-dimensional laminar flow model was adapted to the intestinal absorption of drug and biological substances by carrier-mediated transports in the single perfusion experiments and we investigated the effects of the unstirred water layer on the Michaelis constant and the maximum transport velocity. According to the calculated values, the half saturation concentration at the inlet was larger than the true Michaelis constant at the intestinal wall. The apparent values of the Michaelis constant and the maximum transport velocity obtained by the Lineweaver-Burk plots were larger than the true ones, and the relations were not linear. These deviations increased as the ratio of the maximum transport velocity to the Michaelis constant increased and as the perfusion rate decreased. In the concurrent presence of a passive transport, underestimation of the carrier-mediated transport component of the absorption rate (at steady state) was predicted. It is considered to cause the underestimation of the maximum transport velocity. When water was absorbed (or secreted), the absorption rate increased (or decreased) and did not saturate. This two-dimensional laminar flow model would enable us to analyze the experimental data to determine the true values of the Michaelis constant and the maximum transport velocity.

Absorption↗
PubMed1986

Determination of the membrane permeability coefficient and the reflection coefficient by the two-dimensional laminar flow model for intestinal perfusion experiments.

We performed single perfusion experiments in the small intestine of rats in order to prove that the two-dimensional laminar flow model is suitable to determine the membrane permeability coefficient and the reflection coefficient. We used progesterone as an aqueous-diffusion-limited drug, urea as a membrane transport-limited drug and the tritiated water as an intermediate substance. The membrane permeability coefficient for progesterone was calculated to be 3.6 X 10(-4) cm/s. This value did not change when the thickness of the aqueous diffusion layer was altered by increasing the perfusion rate 10-fold. It was directly demonstrated that the two-dimensional laminar flow model was suitable to analyze the data of intestinal perfusion experiments. Membrane permeability coefficients for urea and tritiated water were determined to be 3.4 X 10(-5) cm/s and 8.9 X 10(-5) cm/s, respectively. In the presence of water absorption with the hypotonic perfusion solution, the reflection coefficient for urea was 0.84. This value is thought to be theoretically reasonable, suggesting the usefullness of the two-dimensional laminar flow model to obtain the reflection coefficient in the intestinal membrane.

Animals↗
PubMed1986

Aneurysm of the extracranial carotid artery.

Aneurysms of the extracranial carotid artery are rare vascular lesions. These aneurysms usually present to the otolaryngologist or vascular surgeon as a cervical or parapharyngeal pulsatile mass. Rupture and hemorrhage are unusual complications. Central nervous system symptoms secondary to embolism or thrombosis, however, are relatively common. Because of these serious complications, surgical resection of the aneurysm with restoration of arterial continuity is the treatment of choice. We describe herein three cases of the extracranial carotid aneurysm treated at the Mie University Hospital, Tsu, Japan, in the past two years. Surgical treatments include end-to-end anastomosis, saphenous vein autograft replacement, and direct closure utilizing an internal shunt, respectively, after resection of the aneurysm. In all patients, the postoperative course was uneventful, and angiography six weeks after the operation demonstrated good blood flow through the repaired artery.

Aged↗
PubMed1986

Effects of potential damaging agents on the microclimate-pH in the rat jejunum.

This study was designed to determine the pH of the intestinal surface in the rat jejunum in an attempt to investigate the effect of potential damaging agents on the microclimate-pH. A significant pH gradient was observed between the mucosal surface and the bulk phase; however, the microclimate-pH usually ranged from 6.5 to 7.5, irrespective of the wide range in the bulk pH. When the bulk pH was either 7.3 or 4, the microclimate-pH was approximately 6.7, while the microclimate-pH was approximately 7.4 when the bulk pH was raised to 9. The distance of the pH gradient was found to be approximately 900-1300 microns. After treatment with ouabain (10 mM) or amiloride (8 mM), or replacement of Na+ with Li+, the microclimate-pH significantly increased compared with the control (buffer solution). Chlorpromazine (2 mM) and ouabain also significantly increased the microclimate-pH, but at the same time, chlorpromazine decreased the bulk pH so that a more marked pH gradient was observed. Both aspirin (10 mM) and acetazolamide (80 mg/kg, iv) significantly decreased the microclimate-pH under the condition of the acidic bulk phase pH. N-Acetyl-L-cysteine (5%) induced marked changes in microclimate-pH, the direction depending upon the bulk phase pH. Neither taurocholic acid (10 mM) nor glucose (10 mM) significantly changed the microclimate pH.

Acetazolamide↗