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Biomedical subjects

M Tsuda

Publications and source records attributed to M Tsuda.

At least 289 records · Page 16Linked to original sources
PubMed1994

A new protocol and criteria for quantitative determination of sensitization potencies of chemicals by guinea pig maximization test.

This paper presents precise sensitization test data of 15 chemicals with a wide spectrum of sensitization potencies, and proposes a new protocol and criteria for quantitative evaluation of sensitization potencies of chemicals. The tests were performed according to the design of Magnusson and Kligman, changing the application concentrations for induction as well as for challenge phases. 3-dimensional relationships between mean response (or sensitization rate), induction and challenge concentrations were found in all chemicals tested. The following 2 values are proposed as a quantitative measure of sensitization potency: (a) the minimum induction concentration that induces a positive response; (b) the challenge concentration that induces a mean response approximately equal to 1.0 among the animals applied with the highest concentration for induction. Both values coincided with each other within the range of 1 order of magnitude in every compound except 2. The values varied by 5 orders or more of magnitude among the compounds, showing a wide variation of sensitization potencies among chemicals. A good correlation was found for every chemical between the value of sensitization potency thus obtained and the residual levels in causative products in human cases of allergic contact dermatitis. A new experimental protocol for obtaining values (a) and (b) is proposed.

Allergens↗
PubMed1994

Identification and characterization of a new plasmid carrying genes for degradation of 2,4-dichlorophenoxyacetate from Pseudomonas cepacia CSV90.

Pseudomonas cepacia CSV90 is able to utilize 2,4-dichlorophenoxyacetate (2,4-D) and 2-methyl-4-chlorophenoxyacetate as sole sources of carbon and energy. Mutants of the strain CSV90 which had lost this ability appeared spontaneously on a nonselective medium. The wild-type strain harbored a 90-kb plasmid, pMAB1, whereas 2,4-D-negative mutants either lost the plasmid or had a 70-kb plasmid, pMAB2. The plasmid pMAB2 was found to have undergone a deletion of a 20-kb fragment of pMAB1. The plasmid-free mutants regained the ability to degrade 2,4-D after introduction of purified pMAB1 by electroporation. Cloning in Escherichia coli of a 10-kb BamHI fragment from pMAB1, the region absent in pMAB2, resulted in the expression of the gene tfdC encoding 3,5-dichlorocatechol 1,2-dioxygenase. After subcloning, the tfdC gene was located in a 1.6-kb HindIII fragment. The nucleotide sequence of the tfdC gene and the restriction map of its contiguous region are identical to those of the well-characterized 2,4-D-degradative plasmid pJP4 of Alcaligenes eutrophus, whereas the overall restriction maps of the two plasmids are different. The N-terminal 44-amino-acid sequence of the enzyme purified from the strain CSV90 confirmed the reading frame in the DNA sequence for tfdC and indicated that the initiation codon GUG is read as methionine instead of valine.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1994

A urease-negative mutant of Helicobacter pylori constructed by allelic exchange mutagenesis lacks the ability to colonize the nude mouse stomach.

The urease of Helicobacter pylori has been proposed to be one of its pathogenic factors. A kanamycin resistance determinant was inserted in a cloned urease gene, and transformation-mediated allelic exchange mutagenesis was carried out to introduce the disrupted gene into the corresponding wild-type chromosomal region of a clinical isolate of H. pylori, CPY3401. The resulting mutant, HPT73, had the null activity of urease. Nude mouse stomachs were challenged with these two isogenic strains to examine the role of urease in pathogenesis. Gastritis was found in the CPY3401-challenged stomachs, from which bacteria indistinguishable from CPY3401 were recovered. There was no gastritis in the HPT73-challenged stomachs, and we could not recover H. pylori from them. These results indicated that H. pylori urease is essential for colonizing the nude mouse stomach.

Alleles↗
PubMed1994

Characterization of a glucose transport system in Vibrio parahaemolyticus.

Cells of a glucose-PTS (phosphoenolpyruvate:carbohydrate phosphotransferase system)-negative mutant of Vibrio parahaemolyticus transport D-glucose in the presence of Na+. Maximum stimulation of D-glucose transport was observed at 40 mM NaCl, and Na+ could be replaced partially with Li+. Addition of D-glucose to the cell suspension under anaerobic conditions elicited Na+ uptake. Thus, we conclude that glucose is transported by a Na+/glucose symport mechanism. Calculated Vmax and Km values for the Na(+)-dependent D-glucose transport were 15 nmol/min/mg of protein and 0.57 mM, respectively, when NaCl was added at 40 mM. Na+ lowered the Km value without affecting the Vmax value. D-Glucose was the best substrate for this transport system, followed by galactose, alpha-D-fucose, and methyl-alpha-glucoside, judging from the inhibition pattern of the glucose transport. D-Glucose itself partly repressed the transport system when cells were grown in its presence.

Biological Transport↗
PubMed1994

Lithium toxicity and Na+(Li+)/H+ antiporter in Escherichia coli.

The lithium ion (Li+) shows toxicity against Escherichia coli cells when present in a high concentration in the environment. Since Li+ is extruded from cells via a Na+(Li+)/H+ antiporter, this antiporter must be involved in the detoxification of Li+. Two Na+(Li+)/H+ antiporters (NhaA system and NhaB system) are known to be present in E. coli. We investigated the properties of the antiporters and the participation of these systems in the detoxification of Li+ using mutants lacking one of the antiporters, or lacking both of them. Although the affinity for Li+ of the two systems was almost the same, the Vmax value for Li+ transport of the NhaA system was about 12 times larger than that of the NhaB system. Wild type cells were unable to grow in the presence of 0.7 M LiCl. Although a wild type cell and a mutant lacking the NhaB system grew in the presence of 0.6 M LiCl, a mutant lacking the NhaA system did not. This second mutant grew in the presence of 0.1 to 0.2 M LiCl. A mutant lacking both the NhaA and NhaB systems could not grow in the presence of 30 mM LiCl.

Escherichia coli↗
PubMed1994

Characterization of the lactose transport system in Citrobacter freundii.

The lactose transport system of Citrobacter freundii was characterized. Both the lactose transport system and beta-galactosidase were induced with either lactose or isopropyl-beta-D-thiogalactopyranoside (IPTG), the latter being the better inducer. The Km values for methyl-beta-D-thiogalactopyranoside (TMG) transport and lactose transport were 0.61 mM and 1.1 mM, respectively, and the Vmax values were 53 nmol/min/mg cell protein and 12 nmol/min/mg cell protein, respectively. Thus, TMG is a better substrate than lactose. Thiogalactopyranoside (TDG) was a very potent competitive inhibitor. Neither Na+ nor Li+ had a significant effect on the TMG transport or the lactose transport. Proton/substrate cotransport (symport) via this system was observed.

Citrobacter freundii↗
PubMed1994

Long-term survival in a patient with malignant carcinoid treated with high-dose octreotide.

Octreotide acetate, a long-acting somatostatin analogue, is effective in controlling and markedly reducing the symptoms of carcinoid crisis. We report a patient with carcinoid syndrome with prolonged survival for 4.5 years with high dose octreotide therapy and survived for 7.5 years after the first flushing, in spite of episodes of severe carcinoid crisis. Dose escalation was required in order to control carcinoid symptoms, and the final dosage was 5,950 micrograms/day. Although administration of such a high dosage of octreotide has never been reported before, we found that octreotide could be used at this dosage safely without inducing serious side effects, and probably prolonged the patient's survival. Our experience with this case indicates that octreotide acetate is an effective drug in controlling carcinoid crisis and prolonging survival without serious side effects.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Essential role of Helicobacter pylori urease in gastric colonization: definite proof using a urease-negative mutant constructed by gene replacement.

OBJECTIVE: To investigate the involvement of urease in Helicobacter pylori colonization in the nude mouse stomach by using a genetically defined urease-negative mutant. METHODS AND RESULTS: Through electroporation-mediated gene replacement, one of the urease genes of an H. pylori strain, CYP3401, was disrupted by insertion of a kanamycin-resistance determinant to construct a stable urease-negative mutant, HPT73. Southern analysis confirmed that gene replacement was achieved. The two isogenic strains were introduced into the stomachs of nude mice, and the number of H. pylori and the histological changes in the stomachs were investigated 1 or 4 weeks after the challenge. Gastritis was present in the CPY3401-challenged stomach, from which bacteria indistinguishable from CPY3401 were successfully recovered. In contrast, no gastritis was found in the HPT73-challenged stomach, and H. pylori was not recovered from these stomachs. CONCLUSION: H. pylori urease is essential for colonization of the nude mouse stomach.

Animals↗
PubMed1994

[Osteoporosis in congenital disorders].

Osteogenesis imperfecta (OI) is the most prevalent osteoporosis syndrome in childhood and is characterized by fractures and skeletal deformities. In almost all individuals, OI results from mutations in one of the two genes (COL1A1 and COL1A2) that encode the chains of type I collagen. OI can be divided into four major groups, type I, II, III, and IV, that differ in clinical presentation, mode of inheritance, radiographic picture, and, for the most part, the biochemical basis of the connective disorder. The molecular basis of OI is mainly discussed.

Collagen↗
PubMed1994

[Subchronic toxicity study of tributoxyethyl phosphate in Wistar rats].

Tributoxyethyl phosphate (TBEP) is widely used in household materials such as plasticizer, floor polish and flame retardant in plastic resins and synthetic rubbers. This compound has been detected at ppb level in underground water. In order to elucidate the toxicity of TBEP, a 14-week oral toxicity study was conducted. Wistar rats (5-weeks old, male & female, 15 rats/group) were given diet containing 0, 0.03, 0.3 or 3.0% TBEP. Suppression of body weight gain was observed in both sexes of the 3.0% group. Serum cholinesterase activity was significantly decreased in both sexes of the 0.3 and 3.0% groups and serum gamma-glutamyl transferase activity was significantly increased in both sexes of the 3.0% group after 5 and 14 weeks exposure. Amylase in serum was also increased in 0.3 and 3.0% group males and 3.0% group females. Absolute and relative liver weights in both sexes were significantly increased in the 3.0% group after 5 and 14 weeks of exposure. Histopathological examination revealed moderate periportal hepatocyte swelling in male rats of the 3.0% group after 14 weeks exposure but this change was not found in male rats given 0.3% or less of TBEP in the diet or in any of the females. These findings indicated that the liver is a target organ for TBEP toxicity. We concluded a no-observed effect level (NOEL) of TBEP in the diet of 0.03% (male: 20 mg/kg/day, female: 22 mg/kg/day) under the conditions of this toxicity study.

Administration, Oral↗
PubMed1994

[A 13-week toxicity study of simultaneous administration of cochineal and aluminum potassium sulfate in rats].

Cochineal (C), a scarlet material extracted from the powdered pregnant insect, Dactylopius Coceus Costa, is used as a color food additive in the form of aluminum lakes. A 13 week subchronic toxicity study was conducted to investigate the effects of simultaneous administration of C and aluminum potassium sulfate (A). Male and female Wistar rats (5-weeks-old, 15 rats/group) were given diets containing 0.75%A and 0.75%C (1.5%AC), 1.5%A and 1.5%C (3%AC), 3%C alone or 3%A alone. The following results were obtained. 1) No toxic symptoms or death occurred in any treated group. Body weight gain in male rats of the 3%A group decreased significantly. 2) Serum levels of phospholipids, triglycerides (TG) and total cholesterol in male rats and TG in female rats fed 3%C, 3%A or 3%AC were significantly decreased at the 13th week. The serum level of glutamate dehydrogenase (GIDH) in male rats treated with 1.5% or 3%AC was increased at the 4th week but no difference from control was observed at the 13th week. 3) No histopathological changes attributable to A and/or C administration were observed. In this 13-week oral toxicity study, no dose-dependent synergistic effects of simultaneous administration of C and A were found except for an increase in serum GIDH.

Administration, Oral↗
PubMed1993

A mutagenesis system utilizing a Tn1722 derivative containing an Escherichia coli-specific vector plasmid: application to Pseudomonas species.

A novel transposon (Tn) mutagenesis system for Gram- non-enteric bacteria was developed which allowed rapid and one-step cloning of the mutated region in Escherichia coli. The Tn constructed was Tn1722-299Km, a Tn1722 derivative containing a KmR gene and the entire sequence of an E. coli-specific plasmid, pACYC184. The hybrid plasmid consisting of Tn1722-299Km and the transfer genes of plasmid R388 was conjugally transferred from E. coli to Pseudomonas putida or P. aeruginosa, and selection of the transconjugants expressing the Tn-specified resistance genes led to isolation of insertion mutants of the recipient strain. The presence of the pACYC184 replicon in the Tn greatly facilitated rapid and easy cloning of the mutated region in E. coli through (i) mini-scale preparation of the genomic DNA from the Tn-inserted mutant, (ii) digestion of the DNA with an appropriate restriction endonuclease, (iii) self-ligation, and (iv) transformation of E. coli to recover the plasmid carrying the Tn-specified resistance marker. This procedure was successfully adapted to clone the Tn-inserted trpBA region of P. putida. Such a cloned region was further employed to isolate the wild-type allele of the trpBA region without construction of a genomic library.

Alleles↗
PubMed1993

GTP-binding protein couples with metabotropic glutamate receptor in bovine retinal on-bipolar cell.

GTP-binding protein (G protein) linking to metabotropic glutamate receptor of bovine retinal on-bipolar cell was studied by use of pharmacologically selective ligands, 2-amino-4-phosphonobutyric acid (APB) on bacterial toxin-catalyzed ADP-ribosylation and GTP gamma S-binding. In contrast to the electrophysiological findings reported, G protein coupling to APB-sensitive glutamate receptor served as a substrate for pertussis toxin but did not for cholera toxin. Several glutamate analogues effective on on-bipolar cell, as well as APB, increased GTP gamma S binding to retinal membranes devoid of rod outer segments. The enhancement of GTP gamma S binding by APB was completely abolished when the membranes were pretreated with pertussis toxin and NAD. These results suggest that, in retinal on-bipolar cell, the G protein which couples metabotropic glutamate receptor to hyperpolarizing response of the cell is sensitive to pertussis toxin.

Animals↗