Biomedical subjects

T Aoki

Publications and source records attributed to T Aoki.

At least 37 records · Page 2Linked to original sources

PubMed1992

Cloning and nucleotide sequence analysis of a chloramphenicol acetyltransferase gene from Vibrio anguillarum.

The chloramphenicol resistant gene (cat) encoding chloramphenicol acetyltransferase (CAT) in a transferable R plasmid (pJA7324) isolated from the fish pathogen Vibrio anguillarum strain PT24 was cloned into the plasmid vector pUC19. The nucleotide sequence analysis of 1,348 base pair DNA identified an open reading frame encoding a protein of 216 amino acid residues with a calculated molecular mass of 25,471 daltons. The predicted amino acid sequences for this cat gene are 37-69% homologous with other CAT proteins of both Gram-negative and -positive bacteria. Colony hybridization performed with a PvuII-BamHI fragment including this cat gene as a probe, revealed that the same or similar chloramphenicol resistance genes existed among V. anguillarum isolates.

Amino Acid Sequence↗

PubMed1992

Nucleotide sequence analysis of the class G tetracycline resistance determinant from Vibrio anguillarum.

The nucleotide sequence of the class G tetracycline resistance determinant previously isolated from Vibrio anguillarum has been determined. Two open reading frames of divergent polarity were identified. A resistance gene (tet A) encodes a protein of 393 amino acid residues (deduced molecular mass of 40.9 kDa), and a repressor gene (tet R) encodes a protein consisting of 210 amino acids with a calculated molecular mass of 23.6 kDa. Based on the deduced amino acid sequences, the proteins of tet A(G) and tet R(G) are about 60% homologous with those of RP1/Tn1721 (class A) and pSC101/pBR322 (class C), and about 50% homologous with Tn10 (class B). The relationship of the tet (G) sequence to five known tetracycline resistance determinants (class A to E) is discussed.

Amino Acid Sequence↗

PubMed1992

Modifying effects of various chemicals on tumor development in a rat wide-spectrum organ carcinogenesis model.

The efficacy of a wide-spectrum organ carcinogenesis model for detection of modification potential of exogenous agents was investigated in F344 male rats. Groups of animals were sequentially injected with N-bis(2-hydroxypropyl)nitrosamine (1000 mg/kg body weight, i.p., in saline, twice in week 1), N-ethyl-N-hydroxyethylnitrosamine (1500 mg/kg body weight, i.g., in distilled water, twice in week 2) and 3,2'-dimethyl-4-aminobiphenyl (75 mg/kg body weight, s.c., in corn oil, twice in week 3) for wide-spectrum initiation of target organs and then given one of 10 test chemicals, comprising 6 hepatocarcinogens and 4 non-hepatocarcinogens, for 12 weeks. All 10 chemicals exerted modifying effects in their respective target organs. Enhancing influence could be detected in the liver and urinary bladder with 2-acetylaminofluorene, ethionine, and 3'-methyl-4-dimethylaminoazobenzene; in the liver and thyroid with 4,4'-diaminodiphenylmethane and phenobarbital; in the esophagus and urinary bladder with N-butyl-N-(4-hydroxybutyl)nitrosamine; in the forestomach and urinary bladder with butylated hydroxyanisole; in the liver with 7,12-dimethylbenz[a]anthracene and in the liver and lung with 3-methylcholanthrene. Inhibitory effects on development of glutathione S-transferase placental form-positive liver cell foci were observed with clofibrate. The results indicate that the present model can be reliably utilized as a whole body medium-term bioassay system for assessment of environmental cancer modifiers.

Animals↗

PubMed1992

Effects of modifying agents on conformity of enzyme phenotype and proliferative potential in focal preneoplastic and neoplastic liver cell lesions in rats.

Development of preneoplastic lesions in the rat liver under the influence of various modifiers was investigated with particular attention to changes in simultaneous expression of altered enzyme phenotype within the lesions (conformity) and proliferation potential. Degree of conformity of marker enzymes such as glutathione S-transferase placental form (GST-P), glucose-6-phosphate dehydrogenase (G6PD), glucose-6-phosphatase, adenosine triphosphatase and gamma-glutamyltranspeptidase was compared with levels of 5-bromo-2-deoxyuridine labeling. After initiation with diethylnitrosamine, rats were administered the hepatopromoter sodium phenobarbital (PB, 0.05%), the antioxidant ethoxyquin (EQ, 0.5%), or a peroxisome proliferator, clofibrate (CF, 1.0%) or di(2-ethylhexyl)-phthalate (0.3%) and killed at week 16 or 32. The PB promoting regimen was clearly associated with increase in the numbers of high conformity class lesions simultaneously expressing three to five enzymes, and elevated proliferation potential. The inhibitor, EQ, in contrast, brought about a time-dependent decrease in conformity so that only 1 or 2 alterations were most commonly observed at week 32. Lesion populations in the peroxisome proliferator- and especially CF-treated cases were characterized by obvious dissociation between degree of conformity and proliferative status. Such treatment-dependent differences were not always correlated with the size of the lesion. The results thus suggested that the conformity and proliferation potential of preneoplastic lesions are dependent on modification treatment. Overall, GST-P was found to be the most reliable marker, although G6PD was less influenced in the peroxisome proliferator cases.

Adenosine Triphosphatases↗

PubMed1992

Effects of total asphyxia on the development of synaptic junctions in the brains of mice.

Using ethanolic phosphotungstic acid staining, we studied the development of synaptic junctions in the brains of mice subjected to total asphyxia. One-day-old mice, Std:ddY strain, were put into a chamber continuously flushed with 100% CO2-gas for 35 min. The surviving mice (28.1%) were used as experimental models, while unasphyxiated littermates served as controls. The synaptic junctions in the frontal motor cortex and hippocampal cortex were studied at 20 and 60 days of age using E-PTA staining, and the numbers of synaptic junctions in both areas were counted. In comparison with the control animals, the frontal motor cortex of the subject mice showed a smaller increase in the number of synaptic junctions, both at 20 and at 60 days of age. In the hippocampal cortex, the number of synaptic junctions seen in the experimental mice brains was similar to that in the controls at 20 days of age; however, the number of synaptic junctions in the treated mice brains showed a slower rate of increase than in the controls at 60 days of age.

Animals↗

PubMed1992

Partial inhibition of skeletal muscle contraction by dantrolene sodium and its modification with perchlorate and Bay K 8644.

The effects of dantrolene sodium (DAN) on the dihydropyridine receptor (DHPR) of the transverse (T) tubule voltage sensor (Ca2+ channel) was studied with single fibers from bullfrog toe muscle. Perchlorate (ClO4-), which acts selectively on the DHPR, overcame DAN-induced inhibition of twitch tension. Bay K 8644, a DHPR agonist, slowed the rate of twitch inhibition by DAN. DAN inhibited twitch tension to a greater extent in Ca(2+)-free solution than in Ringer solution or solution containing Zn2+, whereas twitch inhibition by DAN was less in caffeine-containing solution than in the control. The effects of DAN on Zn(2+)- and caffeine-treated fibers and on fibers in Ca(2+)-free solution suggest that DAN must act near the voltage sensor of the T tubule. However, differences in net twitch inhibition by DAN between control fibers and fibers potentiated by ClO4- or Bay K 8644 suggest that DAN does not bind to the same site as these potentiating agents do. The role of myoplasmic Ca2+ in DAN-induced inhibition of twitch and the effects of DAN on the mechanical threshold and membrane potential in skeletal muscle are discussed.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

Thyroid hormone modulation of the hypothalamic growth hormone (GH)-releasing factor-pituitary GH axis in the rat.

Both thyroid hormone and hypothalamic growth hormone (GH)-releasing factor (GRF) facilitate pituitary somatotroph function. However, the pathophysiological role of thyroid hormone in GRF secretion is less well understood. Thyrotoxicosis, induced by administration of thyroxine (T4) in rats, inhibited both pituitary GH levels and immunoreactive GRF secretion from incubated hypothalamus. At the highest dose of T4 given for 12 d, GRF secretion and pituitary GH decreased by 50 and 39%, respectively. Hypothyroidism induced by thyroidectomy (Tx) enhanced GRF secretion approximately twofold while depleting pituitary GH by greater than 99%. Both of these hypothalamic and pituitary effects were reversed by replacement of T4 but not human GH for 7 or 14 d. Human GH was as potent as T4 in restoring decreased body weight gains or serum insulin-like growth factor-1 levels in Tx rats. These results indicate that at both physiological and pathological concentrations in serum, thyroid hormone acts as an inhibitory modulator of GRF secretion, probably not involving a feedback mechanism through GH. A biphasic effect of thyroid hormone on pituitary GH levels appears to derive from the difference in primary target tissues of hyper- and hypothyroidism, the hypothalamus and the pituitary, respectively.

Animals↗

PubMed1992

Predominant activation and expansion of V gamma 9-bearing gamma delta T cells in vivo as well as in vitro in Salmonella infection.

Gamma delta T cell receptor-positive cells (gamma delta T cells) have recently been implicated to play a role in the protection against infectious pathogens. Serial studies on gamma delta T cells in 14 patients with salmonella infection have revealed that the proportions of gamma delta T cells (mean +/- SD: 17.9 +/- 13.2%) in salmonella infection were significantly increased (P less than 0.01) compared with 35 normal controls (5.0 +/- 2.6%) and 13 patients with other bacterial infections (4.0 +/- 1.4%). Expansion of gamma delta T cells was more prominent in the systemic form (28.9 +/- 10.8%) than in the gastroenteritis form (10.5 +/- 7.9%) of salmonella infection (P less than 0.01). Most in vivo-expanded gamma delta T cells expressed V gamma 9 gene product. Increased activated (HLA-DR+) T cells were observed in all the six patients with the systemic form and four of the seven with gastroenteritis form. Especially in the six with systemic form, gamma delta T cell activation was significantly higher than alpha beta T cell activation at the early stage of illness (P less than 0.01). When peripheral blood lymphocytes from normal individuals were cultured with live salmonella, gamma delta T cells were preferentially activated and expanded and most of them expressed V gamma 9. Purified gamma delta T cells also responded to live salmonella in vitro. The present study suggests that human gamma delta T cells play a role in the protection against salmonella infection in vivo.

Adolescent↗

PubMed1992

Purification and characterization of gamma-enolase from various mammals.

The gamma subunit of enolase (gamma-enolase) was purified from the brain tissues of cow, dog, goat, pig, rabbit, and rat. The purification was achieved in only three steps: ammonium sulfate-precipitation, DE 53 cellulose ion-exchange chromatography, and polyacrylamide gel electrophoresis (PAGE) in a preparative mode. The purification procedure was comparatively more simple than previously reported methods, and the yield of gamma-enolase was sufficient for subsequent structural and immunological analyses. In all mammals, the purified gamma-enolase migrated in sodium dodecyl sulfate-PAGE (SDS-PAGE) with a molecular mass of 46 kilodaltons (kDa), and the immunological cross-reactivity between those gamma-enolases was very strong. The structural homology of these gamma-enolases was examined by peptide mapping using cyanogen bromide cleavage and subsequent two-dimensional electrophoresis. The resulting peptide patterns were highly similar and in cow, dog, and goat, the patterns were almost identical. These results indicate that structural homology, that is, the species non-specificity of gamma-enolase, appears to be very high.

Animals↗

PubMed1992

A novel homoisocarbacyclin analog with potent and long-lasting activity.

A synthesis of a novel and chemically stable homoisocarbacyclin analog, TY-11223 (3), has been accomplished. The analog (3), given intravenously or orally, showed potent and long-lasting activities in inhibiting platelet aggregation and, in addition, a good selectivity in biological activities.

Animals↗

PubMed1992

Development of radioimmunoassay of intact laminin and its clinical evaluation as a tumor marker.

The concentration of laminin including laminin variants in serum samples was measured by a double-antibody radioimmunoassay using intact laminin. The mean level in 92 normal subjects (47 men and 45 women) was defined as 1 unit (U)/ml, and the cut-off value (2 S.D. above the mean) was 1.37 U/ml. Mean laminin level in 391 patients with various malignancies was 1.50 +/- 0.86 U/ml. Laminin levels were elevated in various cancer patients, and in 45.0% (176/391) the values exceeded the cut-off level; in patients with cancer of the stomach or pancreas, positivity rate exceeded 60%. Mean laminin concentration for 130 pregnant women (2.06 +/- 0.65 U/ml) was also significantly higher than that of normal controls, but concentrations for patients with various benign diseases were within a low range (0.55 +/- 0.29-1.10 +/- 0.29 U/ml). In the stomach or pancreas cancer patients, a positive correlation between laminin level and tumor progression or course of the disease was observed. These findings indicate that serum laminin level is potentially useful in the diagnosis and monitoring of certain cancers.

Adult↗

PubMed1992

Effects of morphine on responses of nociceptive ventrobasal thalamic neurons in diabetic rats.

The influence of diabetes on the effects of morphine on the responses of ventrobasal (VB) thalamic neurons to mechanical noxious stimuli were studied in chloral hydrate-anesthetized rats. Animals were rendered diabetic by an injection of streptozotocin (60 mg/kg, i.v.). Morphine (0.3 mg/kg), administered i.v., produced a reduction in the responsiveness of VB thalamic neurons to noxious stimulation in control rats. This effect was reversed by naloxone. In contrast, the inhibitory effects of morphine on the nociceptive responses of VB thalamic neurons were significantly attenuated in diabetic rats, as compared with the controls. However, there were no significant differences in inhibitory potency between diabetic and control rats when morphine (30 nM) was administered intrathecally. It seems likely that these changes in the sensitivity of VB thalamic neurons to morphine are, to some extent, the source of the reduction in the analgesic efficacy of morphine in diabetic rats.

Animals↗

PubMed1992

Simulation of the profile of water, NaCl, and urea transport in the countercurrent multiplication system between thin ascending limb and inner medullary collecting duct.

We simulated the profiles of water, NaCl, and urea transport in the countercurrent multiplication system between thin ascending limb (TAL) and inner medullary collecting duct (IMCD) by a mathematical model consisting of three compartments (TAL, IMCD, and CNW [capillary network]), using phenomenological coefficients for hamsters. They are separated by two membranes with distinct permeability properties. The primary driving force which generates "single effect" has a lower reflection coefficient for urea than for NaCl in IMCD. The difference in urea and NaCl concentrations between CNW and IMCD provides an effective osmotic driving force which is favorable for water absorption from IMCD without physicochemical osmotic gradient. The entry of water in the CNW reduces the concentration in CNW and generates the concentration gradients which are favorable for these solutes to diffuse out of TAL. Thus, the fluid in IMCD is concentrated and that in TAL is diluted. The results of simulation showed that the concentration gradients were generated along the medullary axis, resulting in excretion of hypertonic urine. In addition, we examined effects of changes in phenomenological coefficients of IMCD on this concentrating system. Decreases in permeability and in reflection coefficient for urea and increase in hydraulic conductivity increased the osmotic gradients along each compartment.

Body Water↗

PubMed1992

The role of recombinant human tissue-type plasminogen activator in the treatment of acute pulmonary thromboembolism.

The effect of intravenous recombinant human tissue-type plasminogen activator (tPA) on arterial blood gases was compared with the effect of heparin treatment in acute pulmonary thromboembolism. Fifteen patients received heparin alone (group A), 5 cases were treated with 7.7 x 10(6) I.U. of tPA (group B) and 10 cases with 15 x 10(6) I.U. of tPA (group C) combined with heparin treatment. Arterial oxygen tension before treatment was not significantly different among the three groups. PaO2 was dramatically improved on the 1st day in group C. By the 7th day, PaO2 of group B had improved to the level of group C. However, the PaO2 of group A on the 7th day was not significantly different compared to the pre-treatment value. In group C, post-treatment perfusion lung scintigrams were improved compared to the pre-treatment images, but this was not the case in group B. Treatment with tPA is more effective for acute pulmonary thromboembolism than heparin alone and a high dose of tPA (15 x 10(6) I.U.) leads to rapid improvement in arterial blood gases and lung perfusion images.

Acute Disease↗

PubMed1992

Outbreaks of group A beta-hemolytic streptococcal pharyngitis in children: correlation of serotype T4 with scarlet fever.

We evaluated the clinical features of 121 children who had group A beta-hemolytic streptococcal (GABHS) pharyngitis during 2 outbreaks in the Chikuhou district, Fukuoka, Japan, with respect to T types. During the first outbreak (November 1989-February 1990), T12 (50%) and T22 (27%) were the dominant T types isolated. During the second outbreak (January-April 1991), 64% of the typable strains were T4. Pus on the tonsils was less common and strawberry tongue more common in patients with eruptions than in those without. Skin eruptions were much more common in the patients infected with T4 than with other T types (p < 0.001). Despite a 10-day regimen of amoxicillin, 12/69 patients (17.4%) had evidence of GABHS on repeat cultures. The results suggest that T4 may be associated with a high incidence of scarlet fever. Serotyping should be performed to identify disease carriers and patterns of GABHS infection.

Adolescent↗

PubMed1992

The least number of phosphate groups for crosslinking of casein by colloidal calcium phosphate.

Artificial casein micelles were formed with whole human casein at 20 mM calcium, 17 mM phosphate, and 10 mM citrate. The casein micelles disaggregated by 6 M urea were separated by high performance gel chromatography on a TSK-GEL G4000SW column into crosslinked and monomeric fractions. When the crosslinked casein fraction was analyzed by high performance ionexchange chromatography on a TSK-GEL DEAE-5PW column, a small peak, representing the 3-P component of human beta-casein, and distinct peaks of the 4-P and 5-P components were found. Artificial casein micelles were formed from mixtures of each purified component of human beta-casein and bovine kappa-casein, disaggregated by urea, and separated on a TSK-GEL G4000SW column. The casein aggregates crosslinked by colloidal calcium phosphate were formed in artificial casein micelles of the 3-P and 4-P components. In contrast, no crosslinkage was formed in artificial micelles of the 1-P and 2-P components. The results indicate that at least three phosphate groups are needed for crosslinking of casein by colloidal calcium phosphate.

Animals↗

PubMed1992

[The effects of knowledge and its developmental differences on misconception of weight].

This study aims to examine developmental knowledge related to misconception about weight. Subjects from 5th to 7th graders were asked to reason about justifiable phenomena which never occur in science. After that, before judging weight addition tasks, subjects engaged in some knowledge-generating-tasks to examine which knowledge-generating-tasks relate to misconception. The main results were as follows: (1) Most subjects did not realize untruth about justifiable phenomena, (2) the knowledge which related to misconception were muscular-kinetic-feeling and balance-feeling about weight, and (3) awareness to knowledge-generating-tasks changed with age; 5th graders found the relation about every kind of knowledge-task on chance level responding and 6th and 7th graders found the relation with some justifiable knowledge. Additionally, some 7th graders were not deluded by any knowledge-generating-tasks. These results suggested misconception about weight might relate to inference from some kinds of everyday-knowledge without realizing the inconsistency with science to them. The developmental change of awareness to knowledge-generating-tasks were discussed in terms of coordination subjects' own theory and their use of knowledge.

Adolescent↗

PubMed1992

Re-evaluation of skin lesion distribution in atopic dermatitis. Analysis of cases 0 to 9 years of age.

Distribution of skin lesions was studied in 1,012 patients under 10 years of age, with atopic dermatitis. Of these, 812 (80.2%) had an atopic history; 200 did not. Both categories were divided by age into five subgroups (3-5 months, 6-11 months, 1 year, 2-4 years and 5-9 years) and the incidence of lesions in each of 52 skin regions was compared between the positive and negative history groups and between different age groups. The results were as follows. 1. There was a change in predilection site, from the head (the scalp, face and peri-auricular area) to the neck and flexures (cubital and popliteal fossae) between 1 and 2 years of age. 2. The trunk (shoulders, chest, abdomen and back) was the most common predilection site in both infants and children. 3. Only the upper arm was affected more frequently on the external side than the internal side in all age groups. 4. The nose, mamillae, palms and feet were the least affected areas in all age groups. 5. Incidences in the positive history group were no higher than in the negative group.

Age Factors↗