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Biomedical subjects

K Yamamura

Publications and source records attributed to K Yamamura.

At least 325 records · Page 18Linked to original sources
PubMedDate not supplied

Functional expression of a microinjected Ed alpha gene in C57BL/6 transgenic mice.

The class II major histocompatibility antigens, I-A and I-E, have been detected on the surface of certain immunocompetent cells, including B lymphocytes and monocytes. These molecules are involved in cell-cell interactions in the immune responses. Each class II antigen consists of two subunits, alpha and beta chains, and the genes encoding these subunits have been well characterized at the molecular level. To analyse the regulatory mechanism of E alpha gene expression and the role of the I-E antigen in the regulation of the immune responses, we have produced transgenic mice by microinjecting cloned Ed alpha genes into fertilized eggs of C57BL/6 mice of b haplotype. This strain of mouse carries a deletion in the upstream (5') region of the E alpha gene covering the transcriptional promoter and, therefore, does not express this gene. Interestingly, this genetic defect of the E alpha gene is accompanied by the inability of the host mouse to respond to a certain set of antigens, phenomena generally termed Ir gene control. We report here that the Ed alpha genes are expressed in these transgenic mice to form the I-Ed alpha Eb beta antigen on the surface of B lymphocytes and monocytes and that these I-E antigens are functional in terms of the induction of a mixed lymphocyte reaction and the restoration of immune responsiveness to poly(L-glutamic acid-L-lysine-L-phenylalanine) (GL-Phe).

Animals↗
PubMedDate not supplied

Prevention of autoimmune insulitis by expression of I-E molecules in NOD mice.

The NOD (non-obese diabetic) mouse spontaneously develops insulin-dependent diabetes mellitus (IDDM) characterized by autoimmune insulitis, involving lymphocytic infiltration around and into the islets followed by pancreatic beta (beta) cell destruction, similar to human IDDM. Genetic analysis in breeding studies between NOD and C57BL/6 mice has demonstrated that two recessive genes on independent chromosomes contribute to the development of insulitis. One of the two recessive diabetogenic genes was found to be linked to the major histocompatibility complex (MHC). This is of interest, because the NOD strain has a unique class II MHC: it does not express I-E molecules as no messenger RNA for the alpha-chain of I-E is visible in Northern blot analysis; I-A molecules are not detected with any available monoclonal antibodies or by allo-reactive or autoreactive T-cell clones, although their expression is demonstrated with a conventional antiserum to Ia antigens. To examine whether the unusual expression of class II MHC molecules may be responsible for the development of autoimmune insulitis, we attempted to express I-E molecules in NOD mice selectively, without introducing other genes on chromosome 17 by using I-E-expressing C57BL/6 (B6(E alpha d)) transgenic mice. We report here that the expression of I-E molecules in NOD mice can prevent the development of autoimmune insulitis.

Animals↗
PubMedDate not supplied

New thermal neutron capture therapy for malignant melanoma: melanogenesis-seeking 10B molecule-melanoma cell interaction from in vitro to first clinical trial.

Human melanoma regression by single thermal neutron capture therapy (NCT) using melanoma-seeking 10B compounds has been achieved. Since 1972, the aim of my team has been to synthesize tumor-seeking 10B-compounds possessing selective affinity for specific metabolic activity of the target cancer cells. Once the melanoma takes up these 10B compounds, thermal neutrons, which cause insignificant cell damage, are easily absorbed by nonradioactive 10B, inducing the 10B(n, alpha)7Li reaction and releasing the high LET particles to 14 mu melanoma cell diameter, destroying the tumor without damaging surrounding tissue. Radiobiological and preclinical studies culminated in the first successful human NCT treatment, with no recurrence of the treated melanoma since July, 1987.

Animals↗
PubMedDate not supplied

Estimation of absorbed dose in the covering skin of human melanoma treated by neutron capture therapy.

A patient with malignant melanoma was treated by thermal neutron capture therapy using 10B-paraboronophenylalanine. The compound was injected subcutaneously into ten locations in the tumor-surrounding skin, and the patient was then irradiated with thermal neutrons from the Musashi Reactor at reactor power of 100 KW and neutron flux of 1.2 X 10(9) n/cm2/s. Total absorbed dose to the skin was 11.7-12.5 Gy in the radiation field. The dose equivalents of these doses were estimated as 21.5 and 24.4 Sv, respectively. Early skin reaction after irradiation was checked from day 1 to day 60. The maximum and mean skin scores were 2.0 and 1.5, respectively, and the therapy was safely completed as far as skin reaction was concerned. Some factors influencing the absorbed dose and dose equivalent to the skin are discussed.

Aged↗
PubMedDate not supplied

Effects of high-frequency sound on electrochemical potential using the single-barrel method in guinea pigs.

There are only a few studies investigating the effects of ultrasound on hearing. This paper reports on an experimental investigation on the effect of the long-time exposure to a moderate sound pressure level, high-frequency sound of 16 kHz on the guinea pig inner ear using electrophysiological methods. A decrease of the absolute value of negative potential was observed in the endocochlear potential (EP). The effects of high-frequency sound on EP and electrochemical potential could be explained by a change in the K+ permeability of hair cells.

Acoustic Stimulation↗
PubMedDate not supplied

Effects of high-frequency sound on the guinea pig cochlea. Electrophysiological study using cochlear microphonics, action and endocochlear potential.

There are only a few studies investigating the effect of high-frequency sound on hearing. Authors investigated experimentally the effect of long exposure to high-frequency sound (19 and 25 kHz) below 100 dB (SPL) on guinea pig inner ear. Changes in cochlear microphonics (decrease of maximum output voltage) and especially in endocochlear potential (decrease of the absolute value of negative potential) were observed. The effects of high-frequency sound (10-30 kHz) on the inner ear were discussed.

Action Potentials↗
PubMedDate not supplied

Effect of 4 kHz tone exposure on the guinea pig inner ear: relation in the change of cochlear microphonics, action potential, electrochemical potential and K+ ion concentration induced by noise exposure.

Using 110 male albino guinea pigs, and applying electrophysiological methods, we investigated the effects of 4 kHz tone at moderate sound pressure level on the inner ear at different exposure times (6, 12, 24 and 48 h). Longer than 12 h exposure to 4 kHz tone had a considerable effect on the hearing, inducing a decrease in the maximum output voltage of cochlear microphonics and an increase in the K+ concentration in the endolymph.

Action Potentials↗