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Biomedical subjects

T Takada

Publications and source records attributed to T Takada.

At least 217 records · Page 12Linked to original sources
PubMed1991

Quercetin induces recombinational mutations in cultured cells as detected by DNA fingerprinting.

Quercetin, a flavonoid, is found in many fruits and vegetables. This drug was previously shown to affect the metastatic potential of mouse tumor cells. Mutagenicity of quercetin was examined by means of DNA fingerprint analysis using the Pc-1 probe that efficiently detects mutations due to recombination. Treatment of BMT-11 and FM3A tumor cells with 55 microM quercetin resulted in gain and loss of bands in the fingerprints in both cell lines. The frequencies of the clones having undergone mutation were 3/11 and 6/26, respectively. This suggests that quercetin is mutagenic and induces recombination. This result seems to provide a molecular basis for the phenotypic variations of BMT-11 tumor cells induced by quercetin.

Animals↗
PubMed1991

Expression, localization, and function of an N-terminal half fragment of the rat Na,K-ATPase beta-subunit in HeLa cells.

The N-terminal half of the beta-subunit of rat brain Na,K-ATPase was expressed in HeLa cells transfected with the plasmid pSV2TKneo beta N containing the truncated beta-subunit cDNA to study the assembly and transport of alpha-beta complex. Immunoprecipitation from extracts of metabolically labeled transformed cells demonstrated that the truncated beta-subunit polypeptide (beta N) was neither transported to the plasma membrane nor assembled into an alpha-beta complex with the endogenous alpha-subunit. Cell fractionation experiments showed that the beta N truncated subunit remained unassembled within rough microsomes, suggesting that it never exited from the endoplasmic reticulum (ER). The assembly of the endogenous alpha-and beta-subunits in the beta N-expressing cells was significantly inhibited compared with control cells or with the transformants that did not express the beta N. These results suggest that the N-terminal portion of the beta-subunit interferes with the normal assembly of the endogenous complex which normally takes place in the ER.

Animals↗
PubMed1991

[Clinical evaluation of platelet antagonists on the ex vivo inhibitory effects of platelet aggregation].

It is necessary in clinical to establish the effects of new substances for the primary and secondary prevention of thrombotic illnesses. We measured maximum aggregation after addition of collagen (F.C. 1.7 micrograms/ml) or ADP (F.C. 1.7 mumol/l) in 41 patients without drug treatment, 91 with ticlopidine, 22 with aspirin (ASA); 82-750 mg, 13 with ASA 81 mg, 20 with ticlopidine 100 mg and ASA 81 mg, 13 with cilostazol, 25 with flurbiprofen, 19 with nifedipine and evaluated the ex vivo effect of platelet antagonists. ASA inhibited remarkably collagen-induced platelet aggregation compared with other drugs, but there was significant (p less than 0.01 for 0.5 mumol/l ADP; p less than 0.02 for 1.0 mumol/l ADP) increase of primary aggregation induced by low dose of ADP in 14 healthy volunteers. While ticlopidine only significantly reduced ADP-induced platelet aggregation and we couldn't find dose dependency of ticlopidine (100-300 mg/day) on inhibitory effects of ADP or collagen-induced platelet aggregation. Our results indicate that the administration of one tablet of aspirin for pediatrics (aspirin 81 mg/tab) together with ticlopidine 100 mg is suitable for reduction of platelet aggregation.

Adenosine Diphosphate↗
PubMed1991

[A case of epidural lipomatosis presenting spinal ataxia].

A 41-year-old man was doing well until July 1989, when he noted numbness over soles, followed 4 months later by difficulty in walking. These symptoms were progressively getting worse, and he was admitted to our department on June 12, 1990. General physical examination was unremarkable. Neurologically cranial nerves were intact except old right, traumatic strabismus. Muscle tone and deep tendon reflexes were normal throughout, but bilateral Babinski and Chaddock reflexes were present. Mild weakness of lower extremities were found on muscle testing (4/5). In sensory system, superficial sensory disturbance below T10 was seen, and markedly diminished vibration and position senses of lower extremities were noted. Cerebellar test was intact, although unsteadiness was found on heel-shin test. Romberg sign was definitely positive. His gait was wide-based and ataxic. Laboratory data showed no abnormalities in CBC, chemistry, urinalysis, serological tests and endocrinological examinations. Spinal MRI (Siemens 1.5 Tesla) showed abnormal deposition of epidural fatty tissues compressing spinal cord with flattening of cord from T4 to T8. Spinal ataxia as compressive myelopathy due to epidural lipomatosis was considered and he underwent laminectomy from T4 to T8 with improvement in walking. Epidural lipomatosis is an unusual cause of spinal cord compression, presenting compressive myelopathy, radiculopathy, cauda equina syndrome, intermittent claudication, or back pain. Most of cases were associated with long-term administration of adrenocortical steroid hormone, or underlying diseases, except only 3 cases including ours. This is the first case of spinal epidural lipomatosis presenting progressive gait disturbance due to spinal ataxia.

Adult↗
PubMed1990

Inhibitory effect of androgen on cell death of mouse uterine epithelium.

The protective effect of androgen against the cell death of mouse uterine epithelium was evaluated by examining the retention of 5'-[125I]iodo-2'-deoxyuridine ([125I]IdUrd) incorporated into the whole uterus and the apoptotic index (percentage of the apoptotic cells to the total cells) which is a good index of physiological cell death. Castrated adult female mice were daily injected with oestradiol-17 beta for 3 days, followed by the injection of [125I]IdUrd. Thereafter, these mice were daily injected with only the vehicle or 5 alpha-dihydrotestosterone (DHT), and the 125I-radioactivity retained in the whole uterus was determined. When only the vehicle was injected, the 125I-radioactivity retained in the whole uterus rapidly decreased but injections of DHT reduced the loss of 125I-radioactivity. The effect of DHT on the retention of 125I-radioactivity depended on doses of DHT and was abolished by the pure antiandrogen, flutamide. The apoptotic index of uterine cells was examined by a similar experimental protocol, but without an injection of [125I]IdUrd. Injections of only the vehicle caused marked increases in the apoptotic indices of both luminal and glandular epithelia, but injections of DHT decreased them significantly. The apoptotic index of stroma was not affected by the injection of DHT. The present results indicated that androgen reduces the cell death of mouse uterine epithelium through the androgen receptor.

Animals↗
PubMed1990

Nucleotide sequence determination of chicken glucagon precursor cDNA. Chicken preproglucagon does not contain glucagon-like peptide II.

cDNA clones coding for glucagon were isolated from a chicken pancreas cDNA library, and the nucleotide and amino acid sequences were determined. The amino acid sequence of chicken glucagon was HSQGTFTSDYSKYLDSRRAQDFVQWLMST, which was contained in the 151-amino acid long precursor, being preceded by a signal sequence and an amino-terminal peptide (NH2-peptide) and followed by an intervening peptide and a glucagon-like peptide I (GLP-I). Chicken preproglucagon, however, lacked GLP-II and intervening peptide II which have been shown to be contained in mammalian glucagon precursors.

Animals↗
PubMed1990

Effects of isoflurane on spinal inhibitory potentials.

The effects of isoflurane on segmental spinal cord potentials and heterosegmental slow positive potentials in response to fore- and hindpaw stimulation were studied in the rat. The heterosegmental slow positive potential and late (second) component of the slow positive wave (P2) of segmental spinal cord potential, thought to be primary afferent depolarization, an agent of presynaptic inhibition activated by a feedback loop via supraspinal structures, were greatly suppressed by the anesthetic. In contrast the negative wave (N1) of segmental spinal cord potential, believed to be synchronized activity of dorsal horn neurons, was only minimally affected. No differential effects of isoflurane on spinal cord potentials activated by fore- and hindpaws were found. Thus, the inhibitory activities of the spinal cord, particularly those produced by a feedback loop via supraspinal structures, are suggested to be highly vulnerable to isoflurane.

Animals↗
PubMed1990

Immunocytochemical localization of Na+,K(+)-ATPase in rat retinal pigment epithelial cells.

We investigated quantitatively the ultrastructural localization of the alpha-subunit of Na+,K(+)-ATPase in rat retinal pigment epithelial cells by the protein A-gold technique, using an affinity-purified antibody against the alpha-subunit of rat kidney Na+,K(+)-ATPase. Immunoblot analysis showed that the antibody bound specifically to the alpha- and alpha(+)-subunits of Na+,K(+)-ATPase in the whole retina [the sensory retina plus retinal pigment epithelium (RPE)]. Rat eyes were fixed by perfusion with 4% paraformaldehyde containing 1% glutaraldehyde and embedded in Lowicryl K4M. Ultra-thin sections were incubated with affinity-purified antibody against the alpha-subunit of rat kidney Na+,K(+)-ATPase and subsequently with protein A-gold complex. Light microscopy with a silver enhancement procedure revealed Na+,K(+)-ATPase localized to both the apical and the basal plasma membrane domains of the RPE. Quantitative immunocytochemical analysis by electron microscopy showed a higher density of gold particles on the apical surface than on the basolateral one. Microvilli are so well developed on the apical surface of the RPE that the apical surface profile is much longer than the basolateral one. This means that Na+,K(+)-ATPase is mainly located on the apical surface of the RPE cells.

Animals↗
PubMed1990

Deoxyspergualin directly suppresses antibody formation in vivo and in vitro.

The effect of deoxyspergualin (DSG, NKT-01) on humoral immunity was investigated both in vitro and in vivo. DSG inhibited the primary and secondary responses to T cell-dependent antigens and the response to T cell-independent antigens in thymic and athymic mice. However, natural antibodies in non-sensitized mice were affected less by the administration of DSG. The agent produced a dose-dependent inhibition of B cell proliferation and antibody production to lipopolysaccharide in vitro. Suppression of secondary antibody response was also shown, whenever antigen stimulation was not given, antibody production was not affected. These results suggest that DSG affects the proliferative stage of B lymphocytes in such a way as to inhibit their growth and antibody production.

Animals↗
PubMed1990

The lamina suprachoroidocapillaris of the guinea pig choroid confirmed by the rapid freezing and freeze-substitution method.

There is a compact layer (the lamina suprachoroidocapillaris) between the vascular and the choroidocapillaris layer of the guinea pig and rat choroids. The specimens were treated with the rapid freezing and freeze-substitution method. The choroidal melanocytes and their processes were exclusively built up of several layers, and the arterioles and venules passed through this layer. Numerous nerve terminals were seen throughout this layer, which contained small or large-size synaptic vesicles with dense or light core. These results may facilitate further understanding of the microcirculation in the choroidal architecture.

Animals↗
PubMed1990

Contrast-enhanced intraoperative ultrasonography of small hepatocellular carcinomas.

Nine patients with small hepatocellular carcinomas, ranging up to 2 cm in size (phi: 1.7 +/- 0.2 cm, mean +/- SD), have been encountered, and in two of these patients the cancer was not identifiable by intraoperative ultrasonography. Thus to achieve a better detection of such small hepatic cancers, enhanced intraoperative ultrasonography was tested. Detection by enhanced intraoperative ultrasonography proved successful in all cases. These preliminary results indicate the potential of carbon dioxide as a contrast agent to enhance intraoperative visualization of small liver cancers.

Angiography↗
PubMed1989

Androgen dependency of a tumor produced by a cell line derived from androgen-responsive Shionogi carcinoma 115.

An androgen-dependent tumor (SCC8 tumor) was obtained by inoculating an androgen-responsive cell line derived from the androgen-responsive Shionogi carcinoma 115 (SC115) into mice and then treating the mice with testosterone propionate (TP) at a pharmacological dose (400 micrograms/day). The SCC8 tumor differed in histological appearance from the SC115 tumor and its growth was less stimulated by androgen than that of the SC115 tumor. However, its growth was completely androgen dependent; SCC8 tumors did not develop in castrated mice and regressed when TP treatment was discontinued. The decreased sensitivity of the SCC8 tumor seemed to be attributable in part to its rapid metabolism of testosterone to metabolites with lower androgenic actions. The effects of TP at doses of 0, 100, 200, and 400 micrograms/day on cell division and cell death in SCC8 tumors of medium size were examined by measurements of the mitotic index and the retention of 5-[125I]iodo-2'-deoxyuridine incorporated into the whole tumor. TP increased the mitotic index dose dependently and at all doses reduced the decrease in the retention of 5-[125I]iodo-2'-deoxyuridine. These results suggest that steroids may not only stimulate cell division but also reduce cell death in steroid-dependent tumors.

Androgens↗
PubMed1989

Producing experimental cholangiectasis in dogs by the stripping method.

Despite the general belief that cholangiectasis is caused by biliary stenosis, clinical cases of cholangiectasis exist which do not seem to have biliary stenosis. The purpose of this research was to produce cholangiectasis models without stenosis, and it was found that stripping the surrounding supportive tissues from the extrahepatic bile duct resulted in cholangiectasis without biliary stenosis. The maximum diameter and intraluminal pressure of the bile duct were specifically examined in 24 mongrel dogs before and 4 weeks after stripping. The mean diameter of the bile duct was 2.44 mm before stripping but 6.47 mm 4 weeks after stripping, the latter being significantly larger than the former (p less than 0.001). There were no significant differences in biliary passage according to cholangiomanometry performed before and after stripping, which indicated an absence of biliary stenosis. Histological examination of the bile duct wall and duodenal papilla after stripping showed only mild inflammatory changes. These models could thus be used for the analysis of cholangiectasis without biliary stenosis. Moreover, these models clinically suggest that there are cases of cholangiectasis without biliary stenosis and that sphincteroplasty or choledochojejunostomy should not be applied blindly. In other words, these techniques should only be applied when biliary stenosis has been observed after careful examination.

Animals↗
PubMed1989

Experimental detachment of the canine bile duct to evaluate mechanisms of the dilated bile duct.

The factors inducing biliary dilatation were studied morphologically and functionally by cholangiography and cholangiomanometry in experimental models of chronic biliary dilatation. These models were produced by four methods: Constriction of the lower bile duct (Group 1), formalin infusion into the duodenal papilla (Group 2), detachment of the extrahepatic bile duct (Group 3), and sphincterotomy (Group 4). Biliary dilatation was observed in the first three groups but not in the fourth group. An increase in the intraductal pressure due to blockage of the biliary outflow tract was considered to be the cause of biliary dilatation in Group 1 and 2. In Group 3, the function of the lower bile duct, including the papilla was intact, and reduced resistance of the bile duct wall and due to the loss of the support from the surrounding connective tissue was considered to have induced biliary dilatation. These results suggest that experimental chronic biliary dilatation can be produced by two approaches: 1) Blockage of bile flow in the papilla or the bile duct, and 2) detachment of the bile duct without disturbing bile flow.

Animals↗