Biomedical subjects

H Toda

Publications and source records attributed to H Toda.

At least 127 records · Page 7Linked to original sources

PubMed1991

Tryptophan 65 is essential for hemolytic activity of the thermostable direct hemolysin from Vibrio parahaemolyticus.

The effect of modification of aromatic and ionizable amino acid residues on the hemolytic activity of a thermostable direct hemolysin from Vibrio parahaemolyticus was examined. Tryptophan 65, one of the two tryptophan residues per subunit, was specifically modified with N-bromosuccinimide, resulting in complete loss of hemolytic activity. However, neither nitration with tetranitromethane of one of the nine tyrosine residues nor Nlm-ethoxyformylation of two of the four histidine residues caused any change in hemolytic activity. The hemolysin was fully active upon amidation of two reactive carboxyl group. On the other hand, acetylation of amino groups and the modification of one of the three arginine residues with 1,2-cyclohexanedione resulted in a partial loss of the hemolytic activity. The results suggest that Trp65 is essential for the hemolytic activity of V. parahaemolyticus hemolysin.

Acetic Anhydrides↗

PubMed1991

Disjunctive eye movement evoked by microstimulation in an extrastriate cortical area of the cat.

Slow disjunctive eye movement similar to ocular convergence was evoked by microstimulation in parts of the lateral suprasylvian area (LSA) in alert cats. A tungsten-in-glass microelectrode was used for stimulation, and eye movement was monitored using the magnetic search coil method. The velocity-versus-amplitude relationship of disjunctive eye movement evoked by microstimulation was comparable to that of ocular convergence evoked by presenting a visual target. It is suggested that the LSA plays a role in controlling convergence eye movement.

Animals↗

PubMed1991

Antihypertensive and diuretic effects of YM-09730-5, a new calcium antagonist, in stroke-prone spontaneously hypertensive rats.

1. Effects of consecutive administration of YM-09730-5, (3S)-1-benzyl-3-pyrrolidinyl-methyl (4S)-2,6-dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxy lat e hydrochloride, a new calcium antagonist, for 9 wk on blood pressure and urinary excretion of electrolytes were studied in stroke-prone spontaneously hypertensive (SHRSP) rats. 2. YM-09730-5 (1 and 3 mg/kg per day, p.o.) prevented development of hypertension and produced a significant reduction in blood pressure from the first week of the experiment. Nicardipine (15 mg/kg per day, p.o.) produced almost the same degree of antihypertensive effect as YM-09730-5 at a dose of 3 mg/kg. 3. YM-09730-5 produced significant diuresis and increased urinary excretion of electrolytes throughout the experiment. 4. Chronic administration of YM-09730-5 (3 mg/kg) reduced the severity of glomerular lesions in the kidney and vasculitis in the mesenteric artery. 5. These results demonstrate that YM-09730-5 is a potential antihypertensive drug with a potency about 5 times higher than that of nicardipine.

Animals↗

PubMed1991

A site-directed mutagenesis study of yeast calmodulin.

A site-directed mutagenesis study was carried out in order to understand the regulatory mechanism of calmodulin. We started from the yeast (Saccharomyces cerevisiae) calmodulin gene since it has many differences in amino acid sequence and inferior functional properties compared with the vertebrate calmodulin. Recombinant yeast calmodulins were generated in Escherichia coli transformed by constructed expression plasmids. Three recombinant calmodulins were obtained. The first two were YCM61G, in which the Ca2(+)-binding site 2 (the four Ca2(+)-binding EF-hand structures in calmodulin were numbered from the N-terminus) was converted to the same as that in vertebrate calmodulin, and YCM delta 132-148, in which the C-terminal half sequence of site 4 was deleted. These two recombinant calmodulins had the same maximum Ca2+ binding (3 mol/mol) as yeast calmodulin, which indicates that site 4 of yeast calmodulin was the one losing Ca2+ binding capacity. YCM delta 132-148 could not activate target enzymes, whereas its Ca2+ binding profile was similar to those of yeast calmodulin and YCM61G. Therefore, the structure in site 4 which cannot bind Ca2+ is indispensable for the regulatory function of yeast calmodulin. The complete regulatory function of vertebrate calmodulin can be attained by the combination of 4 Ca2+ binding structures. The negative charge cluster in the central alpha-helix region is suggested to stabilize the active conformation of calmodulin, since the third yeast calmodulin mutant, YCM83E, which had the negative charge cluster, increased the maximum activation of myosin light chain kinase.

Amino Acid Sequence↗

PubMed1991

Topical chemotherapy in human periodontitis using a new controlled-release insert containing ofloxacin. I. Microbiological observation.

The recognition that destructive periodontal diseases may be caused by specific microorganisms in periodontal pockets has led to an increased interest in and usage of antimicrobial agents in periodontal therapy. Recently, a new controlled-release insert containing ofloxacin, a synthetic antibiotic, has been developed. In this study, the controlled-release insert (PT-01) was microbiologically evaluated in combination with or without subgingival mechanical debridement. PT-01 was applied in the periodontal pockets of 27 patients with chronic periodontitis. Three sites with a deep probing pocket depth (greater than or equal to 5 mm) were randomly selected in different quadrants of each patient, and were assigned into three groups, i.e., PT-01 applied (T), placebo applied (P) and control sites (C). Periodontal treatments consisted of supragingival scaling with oral hygiene instruction for the first 2 weeks followed by root planing and subgingival scaling PT-01 was applied weekly on day 0 to 35, and the subgingival plaque samples from each site were collected on d 0, 14, 21 and 42. The dynamics of the subgingival microflora was investigated by dark field microscopy and by anaerobic and aerobic cultivation. In the supragingival scaling period, significant reduction in percentages of spirochetes and motile rods and significant increase of the percentage of coccoid cells were observed only at T sites. In addition, the total viable counts of bacteria, black-pigmented Bacteroides and Fusobacterium species were significantly reduced at T sites. After mechanical subgingival debridement, significant shifts in the proportion and reduction of the viable counts in the subgingival microflora were found at all sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗

PubMed1991

Halothane-induced relaxation of vascular smooth muscle: a possible contribution of increased cyclic GMP formation.

Halothane (0.75 to 2.25%) dose-dependently relaxed the vascular smooth muscle of endothelium-denuded rat aortae previously contracted with KCl, and the relaxing effect was not significantly affected by indomethacin nor dexamethasone, but partly inhibited by methylene blue. The cyclic GMP levels were increased by treatment with halothane (2.25%). It was suggested that halothane-induced relaxation of vascular smooth muscle is partly mediated by cyclic GMP formation.

Animals↗

PubMed1991

Molecular cloning and nucleotide sequencing of the Arthrobacter dextranase gene and its expression in Escherichia coli and Streptococcus sanguis.

A bacterial strain, which assimilated dextran and water-insoluble glucan produced by Streptococcus mutans, was isolated from soil. The bacterium produced and secreted potent dextranase activity, which was identified as Arthrobacter sp. and named CB-8. The dextranase was purified and some enzymatic properties were characterized. The enzyme efficiently decomposed the water-insoluble glucan as well as dextran. A gene library from the bacteria was constructed with Escherichia coli, using plasmid pUC19, and clones producing dextranase activity were selected. Based on the result of nucleotide sequencing analysis, it was deduced that the dextranase was synthesized in CB-8 cells as a polypeptide precursor consisting of 640 amino acid residues, including 49 N-terminal amino acid residues which could be regarded as a signal peptide. In the E. coli transformant, the dextranase activity was detected mostly in the periplasmic space. The gene for the dextranase was introduced into Streptococcus sanguis, using an E. coli-S. sanguis shuttle vector that contained the promoter sequence of a gene for glucosyltransferase derived from a strain of S. mutans. The active dextranase was also expressed and accumulated in S. sanguis cells.

Amino Acid Sequence↗

PubMed1991

[A case of acinar-islet cell tumor of the pancreas body].

Combined carcinoma of the pancreas is very rare. The case of pancreatic tumor featuring both acinar cell and islet cell tumors presented, may be only the fifth case of acinar-islet cell tumor in the world. A 34-year-old-woman visited our hospital complaining of weight loss (8 kg/6 months). A clearly demarcated pancreatic tumor was visualized by ultrasonography, body CT and MRI. Class 3 cells were extracted via ultrasonography guided fine-needle biopsy. Tumor was enucleated on October 5, 1988. Histologic appearance of the tumor by light microscopy was consistent with that of both acinar cell and islet cell tumors. Electron microscopy revealed two distinct populations of zymogen and neuroendocrine granules. The patient is doing well 1 year and 7 months postoperatively with no evidence of liver metastasis or recurrence. This case is significant in terms of the close histogenic relationship between pancreatic exocrine and endocrine components.

Adenoma, Islet Cell↗

PubMed1991

Cerebral cortical and brainstem areas related to the central control of lens accommodation in cat and monkey.

1. Studies on the central nervous system related to lens accommodation in cat and monkey were reviewed. 2. During the last decade, a considerable amount of neurophysiological data on the peripheral innervation of the ciliary muscle, properties of parasympathetic oculomotor neurons and mesencephalic reticular neurons have accumulated. 3. Neurophysiological and anatomical evidence supporting the contribution of the cerebellum to lens accommodation has been obtained. 4. Recently, cerebral cortical neurons in the parieto-occipital cortex with activities related to lens accommodation were found in cat and monkey.

Animals↗

PubMed1991

[Factors regulating venous return: analysis based on the respiratory variations of superior vena caval flow].

Characteristics of venous return and its determining factors were observed using pulsed Doppler echocardiography. Superior vena caval (SVC) flow was regarded as representing venous return. Ten healthy subjects and 23 patients with chronic pulmonary disease were studied. 1. In the healthy subjects, the forward flow was biphasic with dominant systolic (S) wave. Among 23 patients, 18 had normal SVC flow patterns (Group I), while in the remaining 5, SVC flow showed disappearance of the diastolic (D) wave, or both the D and S waves (Group II). 2. The healthy subjects and Group I patients had negative pleural pressures during inspiration and expiration. Consistent findings in Group II patients included positive pleural pressures during expiration and reduction in FEV1.0%. In the normal subjects and Group I patients, right atrial (RA) pressure was less than the pressure of the subclavian vein (ScV) during an entire respiratory phase. However, in Group II, RA pressure was equal to or greater than ScV pressure during expiration, resulting in disappearance or reversal of the S and D waves. 3. Respiratory variation in pleural pressure correlated significantly with that of the S wave (r = 0.77) (p < 0.005), D wave (r = 0.80) (p < 0.005), x descent of RA pressure (r = 0.77) (p < 0.005), and y descent of RA pressure (r = 0.82) (p < 0.005). The present study clearly confirmed that the superior vena caval flow patterns were closely correlated with right heart hemodynamics and truly reflected the effects of pleural pressure.

Aged↗

PubMed1991

[Venous return disturbances in chronic pulmonary disease: a study using pulsed Doppler echocardiography].

Pulsed Doppler echocardiography was used for investigation of respiratory changes of superior vena caval flow in chronic pulmonary disease to analyze the mode of venous return and its regulating factors. The subjects consisted of 55 patients with various pulmonary diseases and 44 healthy controls. 1. In the controls, the velocities of the S and D waves increased during the inspiratory phase. 2. Patients with pulmonary diseases were categorized into 2 groups. One with the mode of the healthy subjects (normal pattern), and the other with disappearance of the D wave or both the S and D waves (abnormal pattern) in the expiratory phase. All patients with restricted ventilation exhibited the normal patterns, while the abnormal patterns were observed in some of the patients with obstructive ventilation, and most of the patients with combined ventilation. 3. The respiratory patterns of the pressure gradients between the right atrium and subclavian vein reflected patterns of the superior vena caval flow well. In cases with abnormal patterns, the right atrial pressure exceeded the subclavian vein pressure in the expiratory phase. 4. The velocity of the A wave at the expiratory phase correlated significantly with pulmonary vascular resistance and with the mean pulmonary artery pressure. In conclusion, the mode of venous return in patients with pulmonary disease varies depending on the mode of the ventilation disturbance and the presence of right ventricular pressure overload, which is most likely caused by the intrathoracic pressure and by right ventricular filling abnormalities.

Aged↗

PubMed1991

A projection of the lens accommodation-related area to the pupillo-constrictor area in the posteromedial lateral suprasylvian area in cats.

The fiber connection between areas related to lens accommodation and to pupillary constriction was studied in the posteromedial lateral suprasylvian area (PMLS) in the extrastriate cortex of the cat. The accommodation-related area was located in the PMLS by microstimulation, and the anterograde tracer Phaseolus vulgaris leucoagglutinin was injected into this area. Anterogradely-labeled fibers and terminals were found in the upper part of the medial bank of the middle suprasylvian sulcus, the area corresponding to the pupillo-constrictor area in the PMLS. The labeling was also found in the fundus of the middle suprasylvian sulcus, the medial bank of the lateral sulcus and the superficial layers of the superior colliculus. It is concluded that the area related to lens accommodation projects to the area related to pupillary constriction in the PMLS.

Accommodation, Ocular↗

PubMed1991

[Comparison of shape recovery ratios in various IOL haptics].

We examined shape recovery ratios of various IOL haptics (polypropylene, polyvinylidene fluoride, polymethylmethacrylate) under conditions resembling clinical use. Experiments were carried out using Ascon lens-holding forceps and compression tests in cylindrical holders. The experimental results indicated that PVDF haptics were superior to PP and 3-piece PMMA haptics. This would suggest the need for surgeons to establish safer implantation techniques in the future by taking into consideration the shape recovery characteristics of the haptics involved. At the same time, further research and development of haptic materials is required by manufacturers.

Biocompatible Materials↗

PubMed1990

cDNA cloning and sequencing for the import precursor of coupling factor 6 in H(+)-ATP synthase from rat liver mitochondria.

The nucleotide sequence of the import precursor of coupling factor 6 (factor 6) of rat liver H(+)-ATP synthase has been determined from a recombinant cDNA clone isolated by screening a rat liver cDNA library with a probe DNA. The sequence was composed of 458 nucleotides including a coding region for the import precursor of factor 6 and noncoding regions of both the 5'- and 3'-sides. The import precursor of factor 6 and its mature polypeptide deduced from the open reading frame consisted of 108 and 76 amino acid residues with a molecular weight of 12,494 and 8,927, respectively. The presequence of 32 amino acids could be the import signal peptide which serves to direct the protein into the mitochondrial matrix.

Adenosine Triphosphatases↗

PubMed1990

cDNA cloning and sequencing for the import precursor of subunit B in H(+)-ATP synthase from rat mitochondria.

The nucleotide sequence of the import precursor of subunit b of rat liver H(+)-ATP synthase has been determined from a recombinant cDNA clone isolated by screening a rat liver cDNA library with a probe DNA. The sequence was composed of 1,124 nucleotides including a coding region for the import precursor of subunit b and noncoding regions of both the 5'- and 3'-sides. The import precursor of subunit b and its mature polypeptide deduced from the open reading frame consisted of 256 and 214 amino acid residues with a molecular weight of 28,867 and 24,628, respectively. The presequence of 42 amino acids could be the import signal peptide which serves to direct the protein into the mitochondrial matrix.

Amino Acid Sequence↗

PubMed1990

Common protein-binding sites in the 5'-flanking regions of human genes for cytochrome c1 and ubiquinone-binding protein.

The single nuclear gene encoding human ubiquinone-binding protein, a subunit of the cytochrome bc1 complex, was isolated previously (Suzuki, H., Hosokawa, Y., Toda, H., Nishikimi, M., and Ozawa, T. (1989) Biochem. Biophys. Res. Commun. 161, 371-378). The 5'-flanking region contains four putative CCAAT boxes, one putative NF-Y-binding site, and one sequence homologous to the AP-1 recognition site, but lacks typical TATA and GC boxes. Three common nucleotide sequences (5'-TATTCAGGT-3', 5'-ATCTGGCT-3', and 5'-TGGTGA(T/G)AG-3', designated Mt1, Mt3, and Mt4, respectively) were found in the 5'-flanking regions of the genes for human ubiquinone-binding protein and for human cytochrome c1, another subunit of the cytochrome bc1 complex. All three sequences are located in the 280-base pair BamHI-HindIII fragment of the ubiquinone-binding protein gene and in the 154-base pair SalI-PstI fragment of the cytochrome c1 gene. Interestingly, a computer-assisted homology search revealed that the SalI-PstI fragment of the cytochrome c1 gene is related to the long terminal repeat of an endogenous retrovirus. Sequences highly homologous to the three Mt-sequences were also found in the 5'-flanking regions of the genes for the beta subunit of human F0F1-ATPase and rat somatic cytochrome c. The Mt1 sequence (TATT-CAGGT) is similar to the GFII recognition site (RTCACGTG) found in the 5'-flanking regions of the yeast nuclear genes for three cytochrome bc1 complex subunits. Gel retardation assay demonstrated that protein factors in a whole HeLa cell extract bound to both of those fragments. At least three different specific binding sites were thought to exist in the fragments. Specific binding of the protein factors to the sites, possibly to the three Mt sequences, may play an important role in the coordinate regulation of the transcription of nuclear genes encoding subunits responsible for mitochondrial oxidative phosphorylation.

Animals↗

PubMed1990

Isolation and characterization of extracellular myeloperoxidase precursor in HL-60 cell cultures.

An extracellular myeloperoxidase precursor of HL-60 cells was purified from the culture supernatant by ammonium sulfate precipitation, DEAE-Sepharose chromatography, and monoclonal antibody affinity chromatography. The purified protein was a glycoprotein of approximately 89 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The amino-terminal amino acid sequence of the protein began at amino acid residue 49 of the 745-amino acid sequence deduced from a myeloperoxidase cDNA, suggesting that the protein consisted of 697 amino acid residues. The implications of the precursor in the processing of myeloperoxidase are discussed.

Amino Acid Sequence↗

PubMed1990

Growth of the malignant and nonmalignant human squamous cells in a protein-free defined medium.

A novel protein-free synthetic medium has been developed for the culture of human squamous cell carcinoma cells. This medium, designated PF86-1, supports the serial subcultivation of six out of nine human squamous cell carcinoma cell lines in a protein-free, chemically defined condition without the adapting culture from serum-containing conditions. These cell lines growing in PF86-1 exhibited nearly equal potency to grow in massive culture without noticeable changes in morphology but presented a significantly decreased level of colony forming efficiency when compared with the cells cultured in serum-containing media, suggesting the implication of some autocrine mechanism. Interestingly, this medium supported the growth of normal human squamous cells of oral mucosa and skin for more than 2 mo. in the primary explant culture in spite of high levels of calcium ion concentration, where the overgrowth of fibroblasts as contaminant was not observed. These results suggest that PF86-1 supports the growth of cells derived from epidermal tissues selectively and provides the same defined condition for growth of malignant and nonmalignant human squamous cells. It seems, therefore, that PF86-1 allows investigations on the products of squamous cell carcinoma cells or on the differences of growth mechanisms between normal and neoplastic human squamous cells.

Carcinoma, Squamous Cell↗