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Biomedical subjects

K Yamamura

Publications and source records attributed to K Yamamura.

At least 199 records · Page 11Linked to original sources
PubMed1992

Synthesis of antibiotic-loaded hydroxyapatite beads and in vitro drug release testing.

Various forms of hydroxyapatite (HAP) materials have been developed for use as bone grafts. Since the risk of local infection is associated with surgery, it seems reasonable to incorporate drugs such as antibiotics into implant materials. We therefore investigated the characteristics of drug incorporation into a spherical porous HAP bead (diameter = 8.48 mm, bulk porosity = 0.439) and its in vitro release behavior. Cefotiam (CTM) was used as a model antibiotic. Because of nonuniform pore distribution in the bead, distribution of CTM was estimated from the amounts of CTM experimentally determined at three different sites: the surface, halfway to the center, and the center of the beads. The results indicated that 90% of the drug was incorporated in the concentric outer 0.387 (radius = 1) section of the bead. CTM was released with a short lag time when the dry HAP bead was placed in water. Incorporation of CTM with egg phosphatidylcholine eliminated initial lag time and decreased the release rate of the drug from the bead. The lipid load was useful in controlling the release of CTM from the beads. In addition, to protect relatively unstable drugs from humidity and avoid contamination of drug-incorporated HAP beads an apparatus was designed with which the beads could be enclosed in vials in vacuo and under aseptic conditions on a bench-scale basis.

Bacterial Infections↗
PubMed1992

Complete prevention of diabetes in transgenic NOD mice expressing I-E molecules.

Previously, we showed that transgenic expression of the MHC (major histocompatibility complex) class II I-E molecules prevented insulitis in non-obese diabetic (NOD) mice at the age of 19 weeks. To rule out the possibility that the I-E expression merely delays the onset of insulitis, we have further characterized the expression and function of the I-E molecule expressed in transgenic NOD mice and confirmed our previous observations. Northern blot analysis showed that the transgenic E alpha d gene was expressed in a pattern similar to the endogenous E alpha d gene in BALB/c mice. The newly expressed I-E molecules were recognized as an alloantigen by the T lymphocytes of normal NOD mice as shown by mixed lymphocyte reaction (MLR). Transgenic NOD mice were resistant to the treatment by cyclophosphamide, which effectively induces diabetes in normal NOD mice, and did not develop diabetes up to 40 weeks of age. On the basis of these findings, we discuss the role of I-E molecules in the prevention of diabetes in NOD mice.

Animals↗
PubMed1992

Transgenic mouse as a tool for the study of autoimmune disease: insulin-dependent diabetes mellitus.

Transgenic mice have been used for analyses of cis-acting elements which are involved in the tissue-specific and developmental-specific expression, for analyses of physiological function of genes, or for the production of a human disease model. This approach is especially successful in the fields of immunology and oncology. Several years ago it was shown that the major histocompatibility complex (MHC) class II gene is identical to the immune response gene by demonstrating that the immune response can be restored by the new expression of class II molecules on immunocompetent cells. Recent evidence suggests that the class II molecule is involved in the generation of autoimmune disease, such as insulin-dependent diabetes mellitus (IDDM). The NOD (non-obese diabetic) mouse is shown to be a mouse model for human IDDM. Concerning the class II genes, the NOD mouse has two characteristic features, the lack of I-E and the presence of unique I-A. It is discussed how the role of class II molecules in the development of IDDM in the NOD mouse can be analyzed. In addition, the transgenic technique can be applied to the study of differentiation and oncogenesis of lymphoid cells. Factors or molecules that affect these processes will also be discussed.

Animals↗
PubMed1992

Developmental and liver-specific expression directed by the serum amyloid P component promoter in transgenic mice.

Transgenic mice were produced by microinjection of a human serum amyloid P component (hSAP) gene or a fusion gene (SS) comprising the promoter for hSAP (nucleotides -600 to -14 from the start codon) and the coding region of the hepatitis B virus surface antigen (HBsAg). In adult mice, both transgenes were expressed only in the liver, and thus the pattern of expression resembled that of the endogenous mouse SAP gene. Both hSAP mRNA and HBsAg were first detected in liver on the second postnatal day. The level of these products increased rapidly and reached the maximum within the first week. These results suggest that the hSAP gene contains a short, cis-acting, developmental, and liver-specific regulatory sequence at the 5' or the 3' end and that this sequence can target expression of the foreign gene.

Animals↗
PubMed1992

Strain dependency of cell-type specificity and onset of lymphoma development in Emu-myc transgenic mice.

c-myc is a nuclear proto-oncogene that, when activated, induces malignancies in a variety of tissues. Most murine plasmacytomas and human Burkitt's lymphomas have been shown to carry a chromosomal translocation involving c-myc and immunoglobulin genes. To study genetic or epigenetic factors that affect myc-induced lymphoid cell tumors, we previously introduced the Emu-myc delta gene lacking its own promoter and first exon into two inbred strains of mice, C57BL/6 and C3H/HeJ. We observed three characteristic features in our transgenic mice. First, T cell lymphoma predominated in the C3H background. Second, both pre-B and B cell lymphoma developed at equal frequency in C57BL/6 transgenic mice. Third, the average age of onset is earlier than that reported by other investigators. To test whether these characteristics are due either to the lack of the promoter region and first exon of the c-myc gene in the construct or to the genetic background of the mice, we introduced Emu-myc gene containing the complete c-myc gene into fertilized eggs of C57BL/6 and C3H/HeJ mice. The cell-type specificity, differentiation-stage specificity and the average age at onset of lymphoma development were not affected by the transgene construct.

Age Factors↗
PubMed1992

[Food poisoning caused by enteroinvasive Escherichia coli (O164:H-)--a case in which the causative agent was identified].

Food poisoning due to "Godofu (Sasayuki tofu)" as a main causative foodstuff which broke out on July 14, 1988. There were 670 out of 918 persons who ingested this food who became ill (incidence 73.0%). The main symptoms were diarrhea (93.4%), fever (77.5%), abdominal pain (64.5%), and vomiting (19.9%). A high degree of fever and watery diarrhea were characteristic of this poisoning. The average latent period was 35 hours with a range of one to 156. The O164:H- strains of enteroinvasive Escherichia coli (EIEC) were detected from 22 of the 32 fecal samples collected from the patients, five of ten samples collected from workers engaged in tofu making, and one sample of left-over Godofu. The virulence of EIEC strains isolated from the patients, workers, and left-over food was confirmed by invasion into HeLa and HEp-2 cells, Sereny test, and ELISA test to detect invasive plasmid-derived protein of the organism (conducted at Tokyo Metropolitan Research Laboratory of Public Health). These EIEC strains were sensitive (less than or equal to 0.19 to 6.25 micrograms/ml) to GM, ABPC, CBPC, CER, CET, NA, PB, MINO, TC and CP as well as KM and OFLX which were used for treatment. However, their susceptibility to FOM varied to some extent (6.25 to 25.0 micrograms/ml) and one strain isolated from a tofu worker was resistant to MINO, TC, FOM and CP (25 to greater than or equal to 100 micrograms/ml). Since investigation revealed that Godofu was left at room temperature about 29 degrees C until ingested, we did a experiment to check the bacterial growth in Godofu under similar conditions at the time of outbreak.(ABSTRACT TRUNCATED AT 250 WORDS)

Escherichia coli↗
PubMed1992

Inhibition of intrahepatic hepatitis B virus replication by antiviral drugs in a novel transgenic mouse model.

Transgenic mice which carry the integrated human hepatitis B virus (HBV) genome and produce HBV particles in the liver were treated with antiviral compounds, and the amount of viral DNA in the liver and serum was monitored by Southern analyses. Mouse alpha interferon (200,000 U per injection, twice daily for 3 days) and a novel nucleoside, oxetanocin G (15 mg/kg of body weight per injection, twice daily for 7 days), inhibited viral DNA synthesis in the liver almost completely. This animal model should prove useful in evaluating anti-HBV agents.

Animals↗
PubMed1992

Study of the effect of 350-Hz tone exposure on electrophysiological function of the inner ear of guinea pigs.

The effects of noise exposure were studied in fifty-nine 4- to 5-week-old albino Hartley guinea pigs with normal hearing (body weight 250-300 g). The following experiments and results were carried out: exposure to 350 Hz pure tones at 115 dB for 40 h and exposure to 350 Hz tones at 120 dB for 64 h. In order to investigate the effects of low-frequency tone exposures on the hearing of the guinea pigs, cochlear microphonics (CM), whole nerve action potentials (AP) and endocochlear potentials (EP) were measured. With a high-sound pressure, a decrease was observed in the CM maximum output voltage in the test frequencies of 2, 4 and 6 kHz while the CM threshold (pseudothreshold) of 6 kHz was elevated. Output voltage of the N1 potential of the AP using a 7-kHz tone burst decreased while the threshold of the N1 potential was elevated. An extension of latency and a decrease in the absolute value of the negative potential in EP were also observed.

Acoustics↗
PubMed1992

Islet amyloid polypeptide/amylin in pancreatic beta-cell line derived from transgenic mouse insulinoma.

We examined the production and secretion of IAPP in a beta-cell line, MIN6, which is derived from an insulinoma obtained by targeted expression of the SV40 T-antigen gene in a transgenic mouse. RNA blot analysis revealed an abundance of IAPP and insulin II mRNA in the cells, findings comparable with those in the pancreas of a normal mouse. The presence of IAPP and insulin was confirmed immunohistochemically and by RIA. Analysis of the reverse-phase HPLC identified IAPP in cells with authentic mouse IAPP. Raising the glucose concentration from 5.6 to 25 mM failed to induce increments in IAPP and insulin II mRNAs. The cells secrete IAPP and insulin for short- and long-term incubations in response to concentration of glucose in the medium. These features resemble those of islet cells from normal animals. This beta-cell line will aid in analyzing the regulation of IAPP gene expression and the mechanisms of IAPP biosynthesis and secretion.

Amyloid↗
PubMed1992

Effect of serum amyloid P component level on transthyretin-derived amyloid deposition in a transgenic mouse model of familial amyloidotic polyneuropathy.

To elucidate the pathogenesis of amyloid deposition associated with familial amyloidotic polyneuropathy (FAP), we developed several transgenic mouse lines carrying the human mutant transthyretin (TTR) gene. We found that human TTR and mouse serum amyloid P component (SAP) are deposited as amyloid in tissues of these mouse lines. Because SAP is a major acute-phase reactant in mice, we asked whether repeated injections of Escherichia coli lipopolysaccharide (LPS) would enhance the amyloid deposition in one of these transgenic mouse lines. During the course of repeated LPS injections, serum levels of SAP in the transgenic mice remained between severalfold to about 50-fold higher than seen in the absence of stimulation. As no significant difference was detected in the onset, progression, and tissue distribution of TTR-derived amyloid (ATTR) deposition between the LPS-stimulated and unstimulated transgenic mice, the induction of SAP synthesis by acute inflammation probably does not affect the onset and extent of ATTR deposition.

Amyloid↗
PubMed1992

Characterization of T-cell tolerance to hepatitis B virus (HBV) antigen in transgenic mice.

We made three different lines of hepatitis B virus (HBV) transgenic mice which express different amounts of hepatitis B e antigen (HBeAg) and/or hepatitis B core antigen (HBcAg) to analyse the cellular mechanisms of HBcAg specific T-cell tolerance. BS10 (official designation, 1.2HB-BS10) transgenic mice, which contain the whole HBV genome, express relatively high amounts of HBeAg in the serum and HBcAg in the liver. SPC mice, which contain hepatitis B virus core and precore gene, express small amounts of HBeAg in the serum but not HBcAg in the liver. SC33 mice, which contain only hepatitis B core gene, do not express HBeAg in the serum but express HBcAg in the liver. BS10 mice showed a very low anti-HBc antibody response after primary and secondary immunizations with recombinant HBcAg compared to transgenic host C57BL/6 (B6) mice. SPC mice showed an almost equal level of anti-HBc antibody response compared to B6 mice. SC33 mice contained anti-HBc antibody even before immunization and showed high titres of anti-HBc antibody response after immunization with HBcAg. Analysis of cellular site(s) of low responsiveness of BS10 mice revealed that proliferating and helper T cells are specifically tolerant to HBcAg. B cells and antigen-presenting cells in BS10 mice were not defective. SC33, SPC and BS10 mice differ a little in their developmental expression of HBc/HBeAg. Our results suggest critical roles of the nature (circulating versus non-circulating) as well as the time of expression of self-antigens in T-cell tolerance.

Animals↗
PubMed1991

Efficient selection for high-expression transfectants with a novel eukaryotic vector.

We have developed a new expression vector which allows efficient selection for transfectants that express foreign genes at high levels. The vector is composed of a ubiquitously strong promoter based on the beta-actin promoter, a 69% subregion of the bovine papilloma virus genome, and a mutant neomycin phosphotransferase II-encoding gene driven by a weak promoter, which confers only marginal resistance to G418. Thus, high concentrations of G418 (approx. 800 micrograms/ml) effectively select for transfectants containing a high vector copy number (greater than 300). We tested this system by producing human interleukin-2 (IL-2) in L cells and Chinese hamster ovary (CHO) cells, and the results showed that high concentrations of G418 efficiently yielded L cell and CHO cell transfectants stably producing IL-2 at levels comparable with those previously attained using gene amplification. The vector sequences were found to have integrated into the host chromosome, and were stably maintained in the transfectants for several months.

Actins↗
PubMed1991

Correction of ornithine transcarbamylase (OTC) deficiency in spf-ash mice by introduction of rat OTC gene.

We introduced rat ornithine transcarbamylase (OTC) gene into OTC-deficient spf-ash mice by mating spf-ash heterozygotes with transgenic mice which carried recombinant DNA composed of 1.3 kb of the 5' flanking region of the gene fused onto rat OTC cDNA. The liver OTC activity of hemizygous spf-ash mice which carried the transgene was about twice that of nontransgenic spf-ash mice, and the small intestinal OTC activity was 6 times higher; the values being 12% and 27% of the control levels, respectively. The transgenic spf-ash mice showed normal hair growth without sparse fur, nearly normalized urinary orotic acid excretion and normalized serum citrulline concentration.

Animals↗
PubMed1991

Specific depletion of the B-cell population induced by aberrant expression of human interferon regulatory factor 1 gene in transgenic mice.

Interferons (IFNs) are well known both as antiviral proteins and as potent regulators of cell growth and differentiation. In fact, IFNs inhibit growth of various normal and transformed cell types. Previously, a nuclear factor, IRF-1 (interferon regulatory factor 1), which binds to type I IFN and some IFN-inducible gene promoters, was identified and cloned. Since the IRF-1 gene is both virus and IFN inducible, an intriguing issue is raised as to whether the IRF-1 gene is functioning in IFN-mediated regulation of cell growth and differentiation. In this study, we generated transgenic mice carrying the human IRF-1 gene linked to the human immunoglobulin heavy-chain enhancer. In the transgenic mice, all the lymphoid tissues examined showed a dramatic reduction in the number of B lymphocytes (B cells). Preparation and analysis of bone marrow cells from the chimeric mice indicated that the bone marrow is the effective site for specific depletion of the B-cell population. In fact, transgenic bone marrow cells cocultured with a bone marrow-derived stromal cell line revealed an altered B-cell maturation pattern.

Animals↗
PubMed1991

Differentiation of growth signal requirement of B lymphocyte precursor is directed by expression of immunoglobulin.

During B cell differentiation, at least three stages can be defined in terms of their growth signal requirement by using two different growth signals, which are recombinant interleukin 7 (IL-7) and a stromal cell clone PA6 which does not produce IL-7; first a PA6 dependent stage, second a PA6 + IL-7 dependent stage and third an IL-7 dependent stage. In order to test the possibility that this differentiation of growth signal requirement is controlled by the expression of functional immunoglobulin molecules, we have investigated the frequencies of PA6 + IL-7 dependent and IL-7 dependent cells which are present in the bone marrow of either mu-chain or kappa-chain gene transgenic mice. In a mu-chain gene transgenic mouse, the frequency of PA6 + IL-7 dependent cells is selectively reduced, while that of IL-7 dependent cells is selectively reduced in a kappa-chain gene transgenic mouse. This result suggests that expression of a functional mu-chain gene drives PA6 + IL-7 dependent cells to differentiate into the subsequent IL-7 dependent stage. Likewise, when mu-chain positive IL-7 dependent cells express a functional light-chain gene, their growth signal requirement changes into an IL-7 unreactive stage.

Animals↗
PubMed1991

Principal component analysis of various respiratory function tests: the relationship between factor score and severity of pulmonary circulatory disorder in chronic obstructive pulmonary disease.

The relationship between pulmonary haemodynamics and values of various respiratory function tests was studied in patients with mild chronic obstructive pulmonary disease (COPD) and the following results were obtained. (1) The value of mean pulmonary artery pressure (mPAP) at rest in COPD patients was slightly elevated to 19.4 mmHg on average compared with our control value of less than 18 mmHg. (2) Analysis of the data of 11 routine respiratory function tests in 88 COPD patients extracted two principal components: an index of the expiratory function and an index for overinflation of the lung. (3) In individual patients, mPAP expressed the severity of pulmonary circulatory disorder roughly inverse to the factor score of the first principal component (index of expiratory function) but not to that of the second principal component (overinflation of the lung). (4) Discriminant analysis was performed in all 88 COPD patients according to data from the 11 respiratory function tests. The probability of mPAP being above or below 18 mmHg was 18.2%. (5) The relationship between the predicted EPOI value and the factor score was similar to that between mPAP and the factor score. EPOI (exercise pulmonary artery pressure-oxygen consumption index) was calculated with the following equation: EPOI = (mPAPex#-mPAPrest)/[VO2ex-VO2rest)/BSA##). On the other hand, EPOIpred was calculated with the prediction equation obtained from multiple linear regression (dependent variable; EPOI, independent variable; respiratory function).

Adult↗