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Biomedical subjects

S Hamada

Publications and source records attributed to S Hamada.

At least 37 records · Page 2Linked to original sources
PubMed1995

Significance of dipyridamole loading in ultrafast x-ray computed tomography for detection of myocardial ischemia. A study in patients with Kawasaki disease.

BACKGROUND AND RATIONALE: To examine the significance of dipyridamole loading as a stress in ultrafast computed tomography (CT) to improve the detection of left ventricular myocardial ischemia. METHODS: Thirty-eight patients with coronary arterial involvement of Kawasaki disease and 18 control subjects received cardiac ultrafast CT with intravenous long-bolus iodinated contrast injection; dipyridamole was loaded in 40 examinations. Early (first-pass) and late (4 minutes) M/Ls (ratio of postcontrast incremental increases in the left ventricular myocardial [M] and luminal [L] CT number) were analyzed. RESULTS: Dipyridamole induced a prominent increase in early M/L of the normal myocardium in control subjects (no loading: 26.8%, dipyridamole: 39.2%; P < 0.001) with small influence on late M/Ls. In ischemic or infarcted myocardium in Kawasaki disease, dipyridamole early M/Ls (20.4%, 16.0%) and late M/Ls showed no difference from corresponding values without loading. Using early M/L with dipyridamole, sensitivity and specificity for detection of ischemic abnormalities were 89% and 100%, respectively. CONCLUSIONS: Dipyridamole-loaded first-pass contrast ultrafast CT was proven to have excellent detectability for myocardial ischemia comparable with stress thallium scintigraphy.

Adolescent↗
PubMed1995

Predicting the growth of aortic aneurysms: a comparison of linear vs exponential models.

The aim of the present study was to determine whether the growth curve of aortic aneurysms had a predictable pattern, specifically whether the growth pattern was better defined by a linear or exponential rate of growth. A twelve-year retrospective review was undertaken. The authors studied 59 patients with aortic aneurysm who have been followed up nonoperatively for more than three years with sequential computed tomographic (CT) scans. There was a total of 74 aortic aneurysms (thoracic aortic aneurysm [TAA]: 30, abdominal aortic aneurysm [AAA]: 44). The diameter of the aortic aneurysm was normalized by dividing by the initial diameter. Exponential (y = A exp [Bt]) and linear (y = C+Dt) regression curves of growth of aneurysmal diameters were calculated, where y is the normalized diameter and t is the time after first CT examination in months. In regression analysis, the values fit well to the exponential growth curves, giving high regression coefficients. Exponential regression equations of TAA and AAA were y = 1.0192 exp (0.0032t), r = 0.720 and y = 1.0129 exp (0.0045t), r = 0.789, respectively. The results in favor of the exponential curve analysis were slightly higher than those favoring the linear curve. This is the first study that showed the growth curves of aortic aneurysms. Aortic aneurysms may grow exponentially rather than linearly with time, and the growth curves might be useful for estimating the natural history or predicting the timing of surgery.

Adult↗
PubMed1995

Preventive effects of recombinant human erythropoietin administration on anemia associated with repeated hemodialysis in nephrectomized dogs.

The preventive effects of recombinant human erythropoietin (rhEPO) administration on progression of anemia were evaluated during hemodialysis in nephrectomized dogs. In control dogs given no rhEPO, anemia gradually progressed with repeated hemodialysis and with little erythropoietic response observed in the bone marrow. In dogs administered with rhEPO, however, an active erythropoietic response was induced in the bone marrow, indicating that anemia due to hemodialysis was being prevented.

Anemia↗
PubMed1995

[Feasibility of the left ventricular volume measurement by acoustic quantification method: comparison with ultrafast computed tomography].

Acoustic quantification (AQ: the real-time automated boundary detection system) allows instantaneous measurement of cardiac chamber volumes. The feasibility of this method was evaluated by comparing the left ventricular (LV) volumes obtained with AQ to those derived from ultrafast computed tomography (UFCT), which enables accurate measurements of LV volumes even in the presence of LV asynergy, in 23 patients (8 with ischemic heart disease, 5 with cardiomyopathy, 3 with valvular heart disease). Both LV end-diastolic and end-systolic volumes obtained with the AQ method were in good agreement with those obtained with UFCT (y = 1.04 x - 16.9, r = 0.95; y = 0.87x + 15.7, r = 0.91; respectively). AQ was reliable even in the presence of LV asynergy. Interobserver variability for the AQ measurement was 10.2%. AQ provides a new, clinically useful method for real-time accurate estimation of the left ventricular volume.

Feasibility Studies↗
PubMed1994

Activation of K+ channels by ritodrine hydrochloride in uterine smooth muscle cells from pregnant women.

This study investigated the mechanism of activation of K+ channels by ritodrine hydrochloride in human myometrial smooth muscle cells. The patch-clamp technique was used for recording single channel currents. Ritodrine (10(-5) M) activated two types of K+ channels in cultured uterine smooth muscle cells from pregnant women: the Ca(2+)-activated K+ (KCa) channel and the ATP-sensitive K+ (KATP) channel. Forskolin (10(-4) M), an activator of adenylate cyclase, and protein kinase A activated the KCa channel. In addition, 10(-4) M GTP activated the KCa channel in inside-out patches using a pipette containing 10(-5) M ritodrine. The KATP channel was activated by protein kinase A, but not by 10(-4) M GTP. The beta-adrenoceptor agonist ritodrine activates two types of K+ channels: the KCa channel via direct gating by GTP-binding proteins and possibly via cAMP-dependent phosphorylation, and the KATP channel possibly via cAMP-dependent phosphorylation. These mechanisms partially explain the relaxing effect of ritodrine hydrochloride.

Cells, Cultured↗
PubMed1994

Inconsistency between the fimbrilin gene and the antigenicity of lipopolysaccharides in selected strains of Porphyromonas gingivalis.

Immunochemical specificity of lipopolysaccharide and the molecular property of the gene encoding the fimbrilin (fimA) of Porphyromonas gingivalis strains were examined using 'fimbriated' strains 381 and HG564 and 'non-fimbriated' strains 381FL and W50. Lipopolysaccharide from strains 381, 381FL and HG564 reacted with monoclonal antibody raised to lipopolysaccharide from strain 381 to give a fused precipitin band by the immunodiffusion test. However, silver staining and Western blotting of lipopolysaccharide clearly revealed a difference in profile of bands between strains 381 and 381FL. On the other hand, lipopolysaccharide from W50 formed another precipitin band and reacted with the antibody, but only at higher concentrations of lipopolysaccharide. The fimA genes in these strains were amplified by polymerase chain reaction and cloned. Sequencing of the fimA gene revealed that the fimA(W50) was almost identical to fimA(HG564), but a notable difference was observed at the start codon of the open reading frame, while the fimA(381FL) was considerably different from fimA of other strains and its open reading frame was found to be missing. These results indicate that the molecular structure of the fimA genes of these strains is not homologous, indicating that molecular modifications in the fimA gene should occur during in vitro passages and maintenance of strains of P. gingivalis in laboratories.

Antibodies, Monoclonal↗
PubMed1994

Porphyromonas gingivalis fimbriae and their synthetic peptides induce proinflammatory cytokines in human peripheral blood monocyte cultures.

Porphyromonas gingivalis fimbriae as well as synthetic peptides that mimic the fimbrial subunit protein, which includes the amino acid sequence XLTXXLTXXNXX, induced high production of proinflammatory cytokines such as interleukin-1 beta, interleukin-6, interleukin-8, tumor necrosis factor-alpha in human peripheral blood monocyte/macrophage cultures. Responses induced by some peptide segments were comparable to those induced by Escherichia coli lipopolysaccharides. A chemically modified peptide analogous to an active peptide segment was found to be antagonistic with regard to interleukin-6 production induced by the native fimbriae. It may be suggested that P. gingivalis fimbriae and their degraded peptides function as proinflammatory agents in vivo, while certain analog peptides inhibited the process.

Amino Acid Sequence↗
PubMed1994

Expression of glutathione S-transferase-pi in human ovarian cancer as an indicator of resistance to chemotherapy.

Expression of glutathione S-transferase-pi (GST-pi) was examined immunohistochemically in relation to the response to chemotherapy with cisplatin in 61 patients with primary ovarian cancer who had not received any chemotherapy before surgery. GST-pi were detected in the cancer tissues of 33 patients (54.1%). Of 28 clinically measurable lesions after surgery, 10 of the 11 tumors (90.9%) showing positive GST-pi staining were drug resistant (no change or progressive disease), whereas 6 of the 17 tumors (35.3%) showing negative staining were drug resistant. This difference in the response rates of the two groups was significant (P < 0.005). The survival period of patients with GST-pi-positive tumors was also significantly shorter than that of those with GST-pi-negative tumors (P < 0.005). These data strongly suggest that GST-pi expression in tumor cells is related to drug resistance of patients with epithelial ovarian cancer and is a useful marker of a poor prognosis.

Adult↗
PubMed1994

Glucose transport and glycolytic enzyme activities in erythrocytes of two-year-old thoroughbreds undergoing training exercise.

D-Glucose transport and cytosolic enzyme activities were measured in erythrocytes from 2-year-old thoroughbreds under continuous training exercise (race horses) and compared with those from untrained horses of various ages (sires, mares and untrained 2-year-old thoroughbreds). The activities of the glucose transport and glycolytic enzymes, hexokinase and pyruvate kinase, in the race horses' erythrocytes were elevated to 2-3.5 times above those of untrained horses. There were no significant differences in plasma glucose, triglyceride or IRI concentrations between the horses in training and untrained horses. The increases in glucose transport and glycolytic enzyme activities in their erythrocytes are considered to reflect an increased metabolic activity in the race horses resulting from the training exercises.

Animals↗
PubMed1994

Conformational stability of alpha-lactalbumin missing a peptide bond between Asp66 and Pro67.

The peptide bond between Asp66-Pro67 of alpha-lactalbumin was cleaved with formic acid (cleaved alpha-lactalbumin). Secondary structural changes of the cleaved alpha-lactalbumin, in which the two separated polypeptides were joined by disulfide bridges, were examined in solutions of sodium dodecyl sulfate (SDS), urea, and guanidine hydrochloride. The structural changes of the cleaved alpha-lactalbumin were compared with those of the intact protein. The relative proportions of secondary structures were determined by curve fitting of the circular dichroism. The cleaved alpha-lactalbumin contained 29% alpha-helical structure as against 34% for the intact protein. Some helices of the cleaved alpha-lactalbumin which had been disrupted by the cleavage appeared to be reformed upon the addition of SDS of very low concentration (0.5 mM). In the SDS solution, the helicities of both the intact and cleaved proteins increased, attaining 44% at 4 mM SDS. On the other hand, the helical structures of the cleaved alpha-lactalbumin began to be disrupted at low concentrations of guanidine hydrochloride and urea compared with that of the intact protein. However, no difference was observed in the thermal denaturations of the intact and cleaved proteins, except for the difference in the original helicities. The helicities of both proteins decreased with an increase of temperature up to 65 degrees C and recovered upon cooling.

Amino Acid Sequence↗
PubMed1994

Singlet oxygen quenching ability of naturally occurring carotenoids.

The singlet oxygen quenching ability of various naturally occurring carotenoids was examined by measuring toluidine blue-sensitized photooxidation of linoleic aci. To assess quenching, the oxidation of linoleic acid was followed by measuring oxygen consumption and ultraviolet absorbance at 235 nm. We found that oxygen quenching increased as the number of conjugated double bonds in the carotenoids increased, but quenching varied with chain structure and functional groups. Acyclic carotenoids enhanced quenching more than did cyclic carotenoids. Conjugated keto groups and the presence of a cyclopentane ring stimulated quenching, while hydroxy, epoxy and methoxy groups showed lesser effects. The photosynthetic bacterial carotenoids, spirilloxanthin and rhodopin, were found to be most effective as quenchers, followed by the cayenne carotenoid, capsorbin.

Animals↗
PubMed1994

PCPA reduces both monoaminergic afferents and nonmonoaminergic synapses in the cerebral cortex.

In order to examine the possible trophic, nontransmitter role of monoaminergic fibers in the adult CNS, synaptic structures were examined in different laminae of the somatosensory cortex of the rat following a p-chlorophenylalanine (PCPA)-induced decrease of monoamine. Synaptic densities were reduced in a dose-dependent fashion by 30-50% in the target area of monoamine fibers following four injections of PCPA made over a 1-week period. Although serotonin- and tyrosine hydroxylase-immunopositive profiles were frequently observed in all laminae of the cerebral cortex, only a few such profiles had the morphology of synapses. Therefore, virtually all of the reduction in synaptic structures following PCPA treatment involved nonmonoaminergic fibers.

Animals↗
PubMed1994

Humoral and cellular immune responses to the fimbriae of Porphyromonas gingivalis and their synthetic peptides.

Subcutaneous injection of fimbriae from Porphyromonas gingivalis strain 381 in Freund's incomplete adjuvant (FIA) resulted in an excellent serum anti-fimbrial immunoglobulin G (IgG) response in guinea-pigs and BALB/c mice. Administration of P. gingivalis fimbriae also elicited distinct cellular immune responses to the fimbriae in terms of ear lobe reaction in BALB/c but not in BALB/c nu/nu mice, and of skin reaction in guinea-pigs. When the guinea-pigs were given a semi-synthetic adjuvant GM-53--sodium beta-N-acetylglycosaminyl-(1-->4)-N-acetylmuramyl-L-alanyl-D-isogl utaminyl- (L)-stearoyl-(D)-meso-2, 6-diaminopimelic acid-(D)-amide-D-alanine--and fimbriae in FIA by subcutaneous injection, more enhanced production of serum anti-fimbrial IgG and stronger cellular immune responses were induced in the guinea-pigs than in those given fimbriae alone. Synthetic peptide FP381(202-221), which corresponds to the amino-acid residue numbers 202-221 based on the amino-acid sequence of fimbrilin from P. gingivalis strain 381, elicited humoral and cellular immune responses in guinea-pigs immunised with the fimbriae or FP381(202-221). Furthermore, subcutaneous administration of synthetic peptide FP381(61-80) with GM-53 induced lesser degrees of humoral and cellular immune responses in guinea-pigs than did FP381(202-221). However, when the fimbriae or FP381(61-80) were administered with bovine serum albumin (BSA), markedly elevated levels of specific anti-BSA antibody were seen in the serum of BALB/c mice. These results clearly indicated that fimbriae from P. gingivalis 381 and their oligopeptide segments induced humoral and cellular immune responses and exhibited immuno-adjuvant activities in guinea-pigs and BALB/c mice.

Adjuvants, Immunologic↗
PubMed1994

Detection of caries-inducing microorganisms in hyposalivated rats without infection of mutans streptococci.

Rampant dental caries was induced in hyposalivated rats fed a high sucrose diet without infection of mutans streptococci, in which increased numbers of lactobacilli and S. aureus were demonstrated in the oral flora. Administration of either penicillin or piperacillin, effective against all isolates of lactobacilli, markedly inhibited the caries induction in these rats, while severe dental caries was induced in hyposalivated rats given vancomycin that is inhibitory against S. aureus. These results suggested that certain lactobacilli might induce dental caries in hyposalivated rats fed a sucrose diet. Three strains of Lactobacillus species isolated from the hyposalivated rats were made resistant to erythromycin. The caries-inducing activity of these erythromycin-resistant lactobacilli was studied in hyposalivated rats giving erythromycin in the drinking water at a concentration of 500 micrograms/ml. After a 61-day experimental period, severe dental caries was induced in hyposalivated rats infected with L. fermentum TY1R. On the other hand, low caries incidence was found in hyposalivated rats infected with either L. acidophilus TY7R or L. plantarum TY3R. These results indicate that L. fermentum may be one of causative agents of dental caries in hyposalivated rats fed a sucrose diet.

Animals↗