Biomedical subjects

T Takeuchi

Publications and source records attributed to T Takeuchi.

At least 1,009 records · Page 56Linked to original sources

PubMed1992

Expression of tyrosinase gene in transgenic albino mice: the heritable patterned coat colors.

To elucidate the regulatory mechanism for tyrosinase gene expression in vivo, we microinjected a mouse tyrosinase minigene, mg-Tyrs-J, into the fertilized eggs of BALB/c albino mice. As a result, we obtained six pigmented founder mice that exhibited non-standard coat color variations as well as the wild-type phenotype. These founder mice were subsequently crossed with BALB/c albino mice to establish the transgenic lines. As a consequence, two primary lines and five sublines have been obtained from four of the six founder mice. We found that not only uniformly pigmented phenotypes but also patterned phenotypes were inherited by their descendants. The possible underlying mechanism of the patterned phenotypes is discussed.

Albinism↗

PubMed1992

Conserved regulatory mechanisms of tyrosinase genes in mice and humans.

In vertebrates, melanin production is restricted to pigment cells. This cell type-specific melanogenesis is considered to involve cell type-specific expression of the tyrosinase gene. Recently, there have been several reports that sequences in the 5' flanking region of the mouse tyrosinase gene are responsible for cell type-specific expression of the transgene in mice. As the first step in the study of the evolution of the regulatory mechanisms for tyrosinase gene function in vertebrates, we constructed a fused gene, hg-Tyrs-J, which includes a 1.0-kb 5' flanking sequence of the human tyrosinase gene fused with mouse tyrosinase cDNA. By introducing the fused gene into fertilized eggs of albino mice, we obtained two mice that exhibited pigmentation in the skin and eyes and established a transgenic line from one of them. Further analyses revealed that the transgene was expressed cell type-specifically in these transgenic mice. We conclude, therefore, that the 1.0 kb 5' upstream region of the human tyrosinase gene contains conserved cis-elements essential for cell type-specific expression of the tyrosinase genes in mice and humans. Results of our study may provide a clue to elucidate the evolutionary process of regulatory mechanisms of the tyrosinase gene.

Animals↗

PubMed1992

The expression of mouse tyrosinase in chick cells in vitro and in vivo when controlled by a constitutive promoter.

Virally introduced mouse tyrosinase expression was checked both in vitro and in vivo in chicken cells and tissues. The results indicate that a constitutive promoter is able to express mouse tyrosinase in a variety of cells and tissues both in vitro and in vivo. Tyrosinase expression is marked by pigment production in situ, which is visible at macroscopic as well as microscopic levels without the use of substrates. It is concluded that tyrosinase can be a valuable marker for tracking gene insertion since it is spontaneously expressed. The expression of tyrosinase in some cells and tissues has a detrimental effect, however, and should be controlled by tissue-specific promoters.

Animals↗

PubMed1992

Expression and transmission of wild-type pigmentation in the skin of transgenic orange-colored variants of medaka (Oryzias latipes) bearing the gene for mouse tyrosinase.

Transgenic fish carrying a reconstructed mouse tyrosinase gene, mg-Tyrs-J, were produced by microinjecting the gene into the oocyte nucleus of an orange-colored variant of medaka (Oryzias latipes). Of 64 oocytes microinjected and subsequently inseminated, 13 embryos developed normally beyond hatching and three of them exhibited brown skin pigmentation in the adult as was commonly observed in the wild type of this species. Light and electron microscopic examination disclosed a ubiquitous distribution of typical melanophores in the skin of these transgenic fish. Judging from their population density and distribution pattern, it was presumed that melanogenesis in these fish was elicited in amelanotic melanophores that resided in the skin of the orange-colored fish of this variant. Immunofluorescence with use of the anti-mouse tyrosinase antiserum lacking reactivity to medaka tyrosinase clearly disclosed that the gene introduced was expressed in the melanophores of transgenic fish. Crosses of female transgenic fish and males from an orange-colored variant yielded offspring exhibiting wild-type or orange-colored pigmentation in a ratio of 1:1, thus implying that mg-Tyrs-J integrated into the medaka genome behaves like a dominant gene. Little melanogenesis was observed in xanthophores, leucophores and iridophores in transgenic fish, suggesting possible specificity in recognition of teleostean cell types (i.e., melanophores) by the regulatory region of the mouse tyrosinase gene.

Animals↗

PubMed1992

[Study on the bacteriological examination of sputum and bronchoscopy specimens from 31 cases with pneumonia due to Chlamydia psittaci].

We carried out the bacteriological examination of sputum and bronchoscopy specimens from 31 cases with pneumonia due to C. psittaci. The results obtained were as follows: 1. The positive culture of sputum and bronchoscopy specimens were 38.7% (12/31). 2. The organisms detected from them were 13 strains of gram-negative bacilli, 2 of gram-positive cocci and one gram-positive bacillus. 3. Significant differences were observed in the white blood cell count between the cases of positive culture and those of normal upper respiratory tract flora (p less than 0.05). From the results we conclude that it would be better that we add the proper antimicrobial drugs to chlamydial antibiotics in the treatment of patients with leukocytosis.

Adolescent↗

PubMed1992

Inhibitory effects of polyethers on human immunodeficiency virus replication.

We examined the inhibitory activities of 10 polyether antibiotics on human immunodeficiency virus (HIV) type 1. These compounds caused concentration-dependent inhibition of HIV replication in primary infected cultures of human T-lymphoblastoid H9 cells. The ratio of 50% effective concentrations for cellular cytotoxicity (MTT assay) to antiviral activity (reverse transcriptase assay) was over 5. Anti-HIV activity was also observed in cultures of monocytic lineage U937 cells chronically infected with HIV.

Anti-Bacterial Agents↗

PubMed1992

High correlation in antibody titers between the Sabin-Feldman dye test and an enzyme-linked immunosorbent assay detecting immunoglobulin G antibodies to the nucleoside triphosphate hydrolase of Toxoplasma gondii.

An enzyme-linked immunosorbent assay to detect immunoglobulin G antibodies against nucleoside triphosphate hydrolase, which is a specific and dominant antigen of Toxoplasma gondii, was developed, and the sensitivity and specificity of the test were compared with those of the Sabin-Feldman dye test. One hundred percent agreement was observed in comparative study between those tests on 37 positive and 50 negative human sera. Antibody titers in the enzyme-linked immunosorbent assay test, which were expressed as the reciprocal of the highest positive dilution of serum, were just 100 times those in the dye test on 81% (30 of 37) of the positive sera.

Animals↗

PubMed1992

Effects of hypoxia, hyperoxia and hypercapnia on graded cerebral ischemic responses in rabbits.

This study was designed to determine how several factors interact to modify the cerebral ischemic pressor response (CIR) in anesthetized rabbits. After the carotid sinus and aortic nerves were bilaterally sectioned, blood flow through the left internal carotid artery (ICF), which was surgically restricted as the sole route of blood supply to the brain, was reduced by a servo-controller during ventilation with room air, and 8% and 90% O2 and 2 and 5% CO2 gas mixtures. Blood flow (MBF), tissue PO2, PCO2, and interstitial pH were measured in the rostral ventrolateral medulla. Internal carotid arterial pressure, tissue PO2, and MBF decreased proportionately as ICF decreased in the range from 4 to 0 ml/min. Hypoxia significantly increased the rise in renal nerve activity (RNA) and CIR caused by cerebral ischemia, while hyperoxia significantly decreased them. Hypercapnia had almost no influence on the increases in RNA and mean arterial pressure produced by cerebral ischemia. CIR showed a much higher correlation with changes in tissue PO2 than with the other factors. We examined how these factors interact to modify CIR and found that central hypoxia is the main factor in producing CIR.

Animals↗

PubMed1992

Neurotrophic effects of fibroblast growth factors on peptide-containing neurons in culture from postnatal rat hypothalamus.

Basic fibroblast growth factor (bFGF) has been thought to act as a neurotrophic factor during early developmental stages in various brain regions, including the hypothalamus. In the present paper, we have studied the effect of bFGF on peptide-containing neurons cultured from the postnatal (1-3 days and 14 days after birth) rat hypothalamus. The addition of bFGF, or acid FGF (aFGF), to serum-free culture medium increased both survival and neurite growth of growth hormone-releasing factor (GRF)-containing neurons. The potency of bFGF was more than 10 times as great as that of aFGF. Insulin-like growth factor I (IGF-I) did not have any significant effect on the survival of GRF neurons. Further, neither IGF-I nor aFGF modified the survival-promoting effect of bFGF on GRF neurons. bFGF promoted the survival of somatostatin- and vasoactive intestinal polypeptide-containing neurons, too.

Animals↗

PubMed1992

Further observations on serial serum immunoreactive inhibin levels in the luteal phase and early gestation after ovarian stimulation for in vitro fertilization and embryo transfer.

Serum immunoreactive inhibin of the luteal phase was measured by radioimmunoassay in 71 patients in vitro fertilization and embryo transfer (IVF-ET). The correlation between the pregnancy outcome and the serial inhibin pattern from the luteal phase to early gestation was studied. In nonconception cycles (n = 35), serum inhibin concentration rose and reached a peak level around 5 or 6 days after oocyte pick-up (OPU), then fell to the level of the early follicular phase. In conception cycles (n = 22), serum inhibin levels rose again 10-15 days after OPU. Serum inhibin levels were significantly higher from 10 days after OPU in multiple pregnancy (n = 5) than in single pregnancy (n = 17). In viable single pregnancy (n = 17), serum inhibin levels were significantly higher than in non-viable pregnancy (n = 14) from 15 days after OPU. Serum inhibin levels in early gestation correlated well with the pregnancy outcome of IVF-ET. These data suggest that inhibin is an important factor for the diagnosis of pregnancy outcome.

Abortion, Spontaneous↗

PubMed1992

Levels of epidermal growth factor in human cord blood.

Levels of epidermal growth factor (EGF) in the cord serum of 13 full-term and 84 preterm infants were measured using a radioimmunoassay. Detectable levels of immunoreactive EGF were present in the cord blood at 23 weeks gestation and rose gradually with increasing gestational age. EGF levels correlated significantly with birth weight and placental weight. In small-for-gestational-age infants with birth weights smaller than 3 SD below the mean, EGF levels were lower than those in appropriate-for-gestational-age infants. These results suggest that EGF may play a role in fetal growth, but low EGF levels may also be the result of growth retardation.

Aging↗

PubMed1992

Noncariogenicity of erythritol as a substrate.

Erythritol is a sugar alcohol produced by Aureobasidium sp. from glucose. It is 75-80% as sweet as sucrose and is also nonhygroscopic. The aim of this study was to evaluate this sugar substitute from a cariological point of view. Erythritol was neither utilized as a substrate for the lactic acid production nor for plaque formation of mutans streptococci (serotypes a-h) and certain oral microorganisms. It was not utilized for water-insoluble glucan synthesis or cellular adherence by glucosyltransferase from Streptococcus mutans PS-14 (c) and Streptococcus sobrinus 6715 (g). Finally, a significantly lower caries score (3.1 +/- 0.5; mean +/- SEM) was observed in specific pathogen-free rats infected with S. sobrinus 6715 and fed with a diet containing 26% erythritol, as compared to control rats fed with a diet containing 26% sucrose (60.5 +/- 2.0). Also, rats provided a diet containing 56% erythritol chocolate (23.8% erythritol) and challenged with S. mutans PS-14 exhibited a significantly lower caries score (6.7 +/- 0.8) compared to the sucrose chocolate group (82.8 +/- 2.8). The main conclusion from this study is therefore that erythritol is a promising sugar substitute from a cariological point of view.

Actinomyces↗

PubMed1992

Dose-dependent enzyme suppression in spleen induced by GM1 (monosialoganglioside 1) administration to mice.

Our previous studies suggested that the administration of exogenous gangliosides to the body modulates enzymatic networks in the brain. In the present study, we tested whether that is the case with another organ, spleen. By testing the dose response relationship, we found that there is a optimum dose for the effect of enzymatic modulation of GM1 (monosialoganglioside 1) administration. Although the optimum level varied depending on each of the examined hydrolytic enzymes, it usually fell in the range around 50 micrograms/kg body weight. The findings led us to conclude that the enzyme-modulating actions of gangliosides come not merely from the bizarre actions in vivo of high molecular exogenous substances.

Animals↗

PubMed1992

Role of PGE2 in neurotransmission from pre- to post-ganglionic hypogastric nerves of guinea pigs.

The hypogastric nerve to guinea pig vas deferens was stimulated pre- or post-ganglionically by adjusting the position of the suction electrode. Both stimulations induced a biphasic contraction consisting of a rapid transient phase and a delayed tonic phase. Indomethacin partially inhibited the contraction induced by pre-ganglionic stimulation, but did not inhibit that induced by post-ganglionic stimulation. Prostaglandin (PG) E2 counteracted the inhibitory effect of indomethacin. Mepacrine also inhibited the contraction induced by pre-ganglionic stimulation. Arachidonic acid and PGE2 both reversed the inhibition. The PGE2-receptor antagonist SC-19220 inhibited the contraction induced by pre-ganglionic, but not post-ganglionic nerve stimulation. These results suggested that endogenous PGE2 is important in neurotransmission in the pelvic ganglion of guinea pigs.

Animals↗

PubMed1992

Role of cyclic AMP in prostaglandin-induced modulation of acetylcholine release from the myenteric plexus of guinea pig ileum.

Prostaglandins (PGs) have modulatory effects on spontaneous and nicotine-induced release of acetylcholine (ACh) from the myenteric plexus of guinea pig ileum. To determine whether cyclic AMP is involved in the mechanisms of these effects, we studied ACh release under conditions that inhibit PG synthesis. Indomethacin (IND), a cyclooxygenase inhibitor, inhibited ACh release concentration-dependently. The effect of the maximally inhibitory concentration of IND (2.8 microM) on nicotine-induced ACh release were reversed concentration-dependently by PGE2, forskolin, 3-isobutyl-1-methylxanthine (IBMX) and 8-bromo cyclic AMP. These compounds caused concentration-dependent reversal of the inhibition of spontaneous ACh release by IND, but their concentrations for restoration of spontaneous release were higher than those for restoration of nicotine-induced release. The effects of PGE2 and forskolin or IBMX were not additive in reversing the inhibition of nicotine-induced ACh release by IND. Neither forskolin nor 8-bromo cyclic AMP alone had any significant effect on either release. These results showed that increase in the level of cyclic AMP in myenteric cholinergic neurons restored ACh release from the tissue whose PG level had been lowered by IND and indicated that endogenous PGs may modulate the level of intraneuronal cyclic AMP.

1-Methyl-3-isobutylxanthine↗

PubMed1992

Action site of the lethal Ay gene in the mouse embryo.

We investigated the lethal effect of Ay gene in embryos at the preimplantation stage in vitro. First, the development until the blastocyst stage and the division of individual cells from 8-cell stage embryos were examined. No difference in development was detected between embryos from the experimental cross (Ay/a x Ay/a) and those from the control cross (a/a x a/a). Therefore, it seems that the abnormality of the Ay/Ay embryo does not appear until blastocyst formation in vitro. We subsequently examined the hatching from zona pellucida of the blastocysts. The hatching ratio of the embryos from the experimental cross was significantly lower than that of the control crosses (Ay/a x a/a, a/a x a/a: p < 0.05). Our observation indicates that deficiency of the Ay/Ay embryo can be detected in vitro at hatching. In order to elucidate the mechanism of the gene action of the Ay, we attempted to rescue the lethal embryos from decreased hatching ratio in vitro. When dbcAMP at the concentration of 1 mM was added to the culture medium, the hatching ratio of blastocysts from the experimental cross increased until the level of those from the control crosses. Since this result indicates that the cAMP content in Ay homozygote seemed to be lower than those in a/a and Ay/a, the cAMP content in individual blastocyst was quantified. It is found that Ay homozygosity was associated with lower level of cAMP. When adenylate cyclase was activated by forskolin and cholera toxin, the hatching ratio was increased. These results seem to suggest that Ay homozygote embryos possess a defect in signal transduction system mediated by adenylate cyclase during hatching.

Adenylyl Cyclases↗

PubMed1992

Visual evoked potentials in guinea pigs with brain lesion.

Visual evoked potentials (VEPs) were recorded in 10 adult male guinea pigs with brain lesion. Lesions were produced in 5 animals by superficial suction of the occipital lobe. The other 5 animals were orally administered with hexachlorophene (about 35 mg/kg/day) for 28 days. In the VEP following the ablation of the occipital lobe, the peaks P10, N20, P55, N75, N140 and P200 disappeared in many cases. The amplitude of the peak N40 decreased to approximately one half its control VEP. In the VEP obtained from the animals administered with hexachlorophene, the peak latencies of N20, P30, P55, N75 and P100 were slightly prolonged after the 7th day following the first administration. On the other hand, there was no change in the latency of N40 during the whole period of administration. The peak-to-peak amplitude showed some variability in different peaks. Histologically, diffuse status spongiosis were found in the white matter of the cerebrum, cerebellum, and brain stem. As described above, the ablation of the occipital lobe caused markedly depressed VEPs, however, the responses to the photic stimulation persisted after the injury. On the other hand, the VEPs of animals administered with hexachlorophene showed a high probability of peak appearance, and a decrease in amplitude was not marked.

Animals↗

PubMed1992

The renotropic effect of ovine luteinizing hormone on subtotally nephrectomized rats.

Some of luteinizing hormone (LH) isoforms can stimulate renal growth. The objective of this study is to determine whether the administration of LH modifies subtotal nephrectomy-induced chronic renal failure. Castrated 3/4-nephrectomized male rats were divided into four groups of seven each and fed a low-protein (6%) diet. Ovine LH with renotropic activity (40 micrograms/day) or vehicle only (control) was given for three weeks or six weeks. Compared with controls, remnant kidney weights (% body weight) in LH-treated rats had increased significantly at three weeks (0.385 +/- 0.019 vs 0.443 +/- 0.052, P less than 0.02), but not at six weeks (0.281 +/- 0.004 vs 0.272 +/- 0.013). 24 h creatinine clearance (ml/day/100 g body weight) increased significantly both by three weeks (242 +/- 58 vs 301 +/- 36, P less than 0.05), and six weeks (323 +/- 55 vs 395 +/- 10, P less than 0.01). Urinary thromboxane B2 excretion increased in LH-treated rats, suggesting that hemodynamic changes may play a role in increasing creatinine clearance. Our results suggest that renotropically active oLH stimulated the glomerular function in castrated rats with reduced renal mass. Further study may clarify its clinical usefulness.

Animals↗