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Biomedical subjects

K Doi

Publications and source records attributed to K Doi.

At least 199 records · Page 11Linked to original sources
PubMed1999

Quantitative evaluation of vessel tracking techniques on coronary angiograms.

Accurate, automated determination of vessel center lines is essential for two- and three-dimensional analysis of the coronary vascular tree. Therefore, we have been developing techniques for vessel tracking and for evaluating their accuracy and precision in clinical images. After points in vessels are manually indicated, the vessels are tracked automatically by means of a modified sector-search approach. The perimeters of sectors centered on previous tracking points are searched for the pixels with the maximum contrast. The sector size and radius are automatically adjusted based on local vessel tortuosity. The performance of the tracking technique in regions of high-intensity background is improved by application of a nonlinear adaptive filtering technique in which the vessel signal is effectively removed prior to background estimation. The tracking results were evaluated visually and by calculation of distances between the tracked and user-indicated centerlines, which were used as the "truth." Two hundred and fifty-six coronary vessels were tracked in 32 angiograms. Vessels as small as 0.6 mm in diameter were tracked accurately. This technique correctly tracked 255/256 (>99%) vessels based on an average of 2-3 indicated points per vessel. The one incorrect tracking result was due to a low signal-to-noise ratio (SNR<2). The distance between the tracked and the "true" centerlines ranged from 0.4 to 1.8 pixels, with an average of 0.8 pixels. These results indicate that this technique can provide a reliable basis for 2D and 3D vascular analysis.

Coronary Angiography↗
PubMed1999

Iterative image warping technique for temporal subtraction of sequential chest radiographs to detect interval change.

A temporal subtraction technique has been developed to assist radiologists in the detection of interval changes on chest radiographs. Although the overall performance of the current temporal subtraction technique is relatively good, severe misregistration errors, mainly due to AP inclination and/or rotation, are observed in some cases. In order to reduce these errors, we attempted to improve the subtraction scheme by applying an iterative image warping technique. In cases obtained with the new temporal subtraction technique 177 (97.8%) of 181 showed adequate, good, or excellent quality. We also found that 156 (86.2%) of cases obtained with the new scheme showed improvements in the quality of the subtraction images compared with the previous scheme. The results indicate that the performance of the temporal subtraction technique was greatly improved by use of the iterative image warping technique.

Databases, Factual↗
PubMed1999

Computer-aided diagnosis of pulmonary nodules: results of a large-scale observer test.

PURPOSE: To determine the effect of computer-aided diagnosis (CAD) on the accuracy of pulmonary nodule detection. MATERIALS AND METHODS: Twenty abnormal chest radiographs, each with a single nodule, and 20 normal radiographs were digitized with a laser scanner. These images were analyzed by using a computer program that indicates areas that may represent pulmonary nodules. The radiographs were displayed on computer workstations in randomized order, and an observer test was performed. One hundred forty-six observers participated, including 23 chest radiologists, 54 other radiologists, 27 radiology residents, and 42 nonradiologists. Cases were interpreted first without and then with the use of CAD. The observers' responses were recorded on a continuous confidence rating scale. Detection accuracy both with and without CAD was evaluated with receiver operating characteristic analysis. RESULTS: The detection accuracy was significantly higher for all categories of observers when CAD was used (chest radiologists, P = 8 x 10(-6); other radiologists, P = 2 x 10(-16); radiology residents, P = 6 x 10(-7); and nonradiologists, P = 8 x 10(-9)). CONCLUSION: CAD has the potential to improve diagnostic accuracy in the detection of lung nodules on digital radiographs.

Diagnosis, Computer-Assisted↗
PubMed1999

Expression of an inwardly rectifying K(+) channel, Kir4.1, in satellite cells of rat cochlear ganglia.

Satellite cells are glial cells wrapped around somata of sensory and autonomic ganglion neurons. Neither their functional roles nor electrical properties have been fully clarified so far. Using immunohistochemistry, we found that inwardly rectifying K(+) channel subunit Kir4.1 (also called Kir1.2 or K(AB)-2) was expressed prominently in the satellite cells of cochlear ganglia. The Kir4.1 immunoreactivity was localized specifically at the myelin sheaths of satellite cells wrapping the somata of the ganglion neurons. Developmental expression of Kir4.1 in satellite cells paralleled development of the action potential in the auditory nerve. These results suggest that this channel in satellite cells may be responsible for the regulation of K(+) extruded from the ganglion neurons during excitation.

Aging↗
PubMed1999

Intracellular gradients of O2 supply to mitochondria in actively respiring single cardiomyocyte of rats.

We demonstrated in a previous study [Takahashi, E., K. Sato, H. Endoh, Z.-L. Xu, and K. Doi. Am. J. Physiol. 275 (Heart Circ. Physiol. 44): H225-H233, 1998] that significant radial gradients of intracellular PO2 may be produced in an uncoupled actively respiring, single isolated cardiomyocyte of the rat. The present study was designed to further determine whether such intracellular PO2 gradients can be a limiting factor of oxidative metabolism in uncoupled cardiomyocytes. The NAD(P)H fluorescence of a single cardiomyocyte was captured by a digital charge-coupled device camera and quantitated with a subcellular spatial resolution by a ratio-imaging technique. In the conditions that we demonstrated significant radial PO2 gradients (cells treated with 1 microM carbonyl cyanide m-chlorophenylhydrazone and superfused with 2.09% or 3.14% O2 gas at 27 degreesC), we demonstrated significant augmentation of NAD(P)H fluorescence near the core of an individual cell. The heterogeneous fluorescence pattern was not found in the control cell, whereas fluorescence intensity averaged over the cell was increased by hypoxia. These results suggest the possibility that oxidative phosphorylation near the core of actively respiring, uncoupled cardiomyocytes may be severely suppressed due to insufficient diffusional oxygen supply (hypoxic core) even if regions near the sarcolemma are adequately oxygenated.

Animals↗
PubMed1999

Impairment of EDR by a long-term PDGF treatment in organ-cultured rabbit mesenteric artery.

Platelet-derived growth factor (PDGF) has been shown to act chronically on blood vessels to regulate not only proliferation but also vascular tone. These effects may be at least partly due to the chronic effect of PDGF on vascular endothelium. To evaluate this possibility, we examined the effects of PDGF on the endothelium-dependent relaxation (EDR) and total RNA for endothelial nitric oxide (NO) synthase (eNOS) using an organ culture system. In rabbit mesenteric arteries cultured in a serum-free medium for 1 wk, amplitude of the substance P-induced EDR did not change, whereas dependency of the EDR on NO (approximately 60.0% vs. 18.9%) and the total amounts of recoverable eNOS mRNA estimated by RT-PCR were increased compared with those in freshly isolated arteries. Culture with PDGF for 1 wk decreased the relaxant effect of substance P and ionomycin (P < 0.01 compared with the arteries without PDGF), NO production estimated by bioassay (P < 0.01), and eNOS mRNA level, whereas the sodium nitroprusside-induced relaxation did not change. These results suggest that PDGF has a chronic effect on vascular endothelium to decrease eNOS mRNA and NO production and to impair NO-dependent EDR.

Animals↗
PubMed1999

Generalized dermal dysplasia and perifollicular mucinosis in a dog.

Multiple nodules 0.5-2 cm in diameter were observed in the dorsal skin of a 1.5-year-old male castrated mongrel dog. Histopathologically, perifollicular mucinosis and clusters of small cells with a dense, round nucleus and scant cytoplasm were seen. The small cell clusters were present in the dermis near the epidermal basal layer or surrounding hair follicles. These cells demonstrated different staining patterns for vimentin and keratin depending on their location; ultrastructurally, they were poor in organelles and connected to each other with cytoplasmic projections. These findings suggested that they were immature epithelial cells. The case was diagnosed as generalized dermal dysplasia and perifollicular mucinosis.

Animals↗
PubMed1999

Possible involvement of DNA methylation in 5-azacytidine-induced neuronal cell apoptosis.

Eight chemicals that are cytidine analogues or nucleosides (5-azacytidine (5AzC), 5-azadeoxycytidine, 6-azacytidine, 5-azacytosin, cytidine, 3-deazaadenine, 3-deazauridine and 6-azauridine) were examined for the ability to induce neuronal apoptosis. 5AzC and 5-azadeoxycytidine induced apoptosis in the brain and spinal cord of the fetuses at 24 hr after the injection to dams, while the other chemicals tested failed to induce apoptosis. In the system of PC12 cells, only 5AzC induced apoptosis, and other chemicals failed to provoke morphological and biochemical changes characteristic of apoptosis. 5AzC, 5-azadeoxycytidine and 6-azacytidine failed to induce apoptosis in C6 cells. Gel electrophoresis after MspI or HapII digestions revealed no apparent evidence of DNA demethylation after 5AzC-treatment in either fetal brains or PC12 cells. These results indicate that DNA demethylation is possibly involved in 5AzC-induced neuronal apoptosis although no direct evidence of DNA demethylation was obtained.

Animals↗
PubMed1999

T-2 toxin-induced acute skin lesions in Wistar-derived hypotrichotic WBN/ILA-Ht rats.

Acute lesions in the dorsal skin topically applied with T-2 toxin (10 microliters of 0.5 mg/ml-solution to 1 cm2) were examined in Wistar-derived hypotrichotic WBN/ILA-Ht rats up to 24 hours after treatment (24HAT). In the epidermis, depression of basal cell proliferating activity was detected at 3HAT by immunostaining for proliferating cell nuclear antigen (PCNA), and the percentage of PCNA-positive basal cells decreased thereafter. At 12HAT, in addition to intracytoplasmic edema of spinous cells, acidophilic degeneration of basal cells characterized by shrinkage of cell body with acidophilic cytoplasm and pyknotic or karyorrhectic nuclei became prominent. Most of these nuclei were positive for TUNEL which is a widely used immunostaining for the in situ detection of fragmented DNA, i.e. apoptosis, and the percentage of TUNEL-positive basal cells increased thereafter. The nuclei of these basal cells also showed ultrastructural changes characteristic for apoptosis. On the other hand, in the dermis, infiltration of inflammatory cells including mast cells started at 3HAT and increased thereafter. In addition, capillary and small vessel endothelial degeneration developed at 6HAT and progressed thereafter. These results suggest that T-2 toxin directly affects the epidermis and produces apoptosis in basal cells.

Animals↗
PubMed1999

The development of bone changes induced in rats by recombinant human granulocyte colony-stimulating factor is suppressed by bisphosphonate.

We have previously demonstrated that high doses of recombinant human granulocyte colony-stimulating factor (rhG-CSF) induce bone changes characterized by osteoclastic bone resorption and osteogenesis due to intramembranous ossification in rats. In this communication we examined the effects of a pretreatment with 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP), which is a powerful inhibitor of osteoclastic bone resorption, on bone changes induced by rhG-CSF in order to investigate the relation between osteoclastic bone resorption and osteogenesis. AHPrBP (5 mg/kg/day) was subcutaneously given to 6-week-old rats for 2 days. From the following day of the final injection of AHPrBP, rats received a subcutaneous injection of rhG-CSF (1,000 micrograms/kg/day) for 14 days, and the femur and tibia were evaluated histopathologically. By the analysis of peripheral blood leukocyte counts, spleen weights and bone marrow findings, the pretreatment with AHPrBP had no effect on the activation of hematopoiesis related to the major pharmacological activity of rhG-CSF. In the rats treated with rhG-CSF alone, accelerated osteoclastic bone resorption and osteogenesis due to intramembranous ossification were observed in the trabeculae of metaphyseal spongiosa. The accelerated osteoclastic bone resorption induced by rhG-CSF was suppressed by the pharmacological activity of AHPrBP. Furthermore, the osteogenesis induced by rhG-CSF was also suppressed by AHPrBP. These results suggest that the osteogenesis induced by rhG-CSF is a sequential reaction of accelerated osteoclastic bone resorption, and moreover that the main action of rhG-CSF on bone is an acceleration of osteoclastic bone resorption.

Animals↗
PubMed1999

Apoptosis in the developing mouse embryos from T-2 toxin-inoculated dams.

T-2 toxin (3 mg/kg b.w.) was orally inoculated to pregnant mice at 11 days of gestation to examine the effect of T-2 toxin on the developing embryos. At 24 hours after T-2 toxin-inoculation, moderate pyknosis or karyorrhexis was generally observed in some layers of the central nervous system, caudal sclerotomic segment, caudal region of the tongue to pharyngeal- to laryngeal-mesenchyma, trachea and facial mesenchyma. These pyknotic or karyorrhectic nuclei were strongly stained by the modified TUNEL method widely used for the in situ detection of apoptotic nuclei and also showed ultrastructural changes characteristic for apoptosis. This is the first report of mycotoxin-induced apoptosis in embryos.

Animals↗
PubMed1999

Clinical analysis of hypertrophic cardiomyopathy which evolved into dilated phase during long-term follow-up.

The aim of the present study was to analyze the incidence, clinical features and prognosis of patients with hypertrophic cardiomyopathy (HCM) which evolved into dilated phase HCM. The medical records of 43 patients with HCM followed up for at least 10 years were analyzed retrospectively. The patients were divided into two groups: group A consisting of patients with dilated-phase HCM defined by a left ventricular end diastolic dimension (LVDD) of 55 mm or more and a left ventricular ejection fraction (LVEF) of less than 50% obtained by echocardiography, and group B, consisting of patients with HCM that did not evolve into dilated phase HCM. During the mean follow-up of 16.7 years, 10 patients (23.3%) evolved into dilated phase HCM (group A) while the remaining 33 patients (76.7%) did not (group B). Ventricular tachycardia (VT) occurred in 7 of the 10 patients (70.0%) in group A and in 5 of the 33 patients (15.2%) in group B (p < 0.001). An increase in LVDD and decreases in LVEF and SV1 + RV5 in the electrocardiogram were observed during the early phase of the follow-up period in group A, while these changes were gradual in group B. Cardiac death occurred in 5 (50.0%) of the 10 patients in group A and in 2 (6.1%) of the 33 patients in group B (p < 0.001). In conclusion, dilated-phase HCM is characterized by decreases in LVEF and SV + RV5 and an increase in LVDD during the early phase of follow-up period, and is associated with an increased incidence of VT and a poor prognosis.

Adolescent↗
PubMed1999

Diurnal changes in intraepithelial lymphocytes (IELs) in the small intestine of mice.

Diurnal changes in small intestinal intraepithelial lymphocytes (IELs) were examined in 8- to 10-week-old BALB/cA male mice. The ratio of T cell subsets expressing CD8 alpha alpha homodimer/CD8 alpha beta heterodimer was found to be higher in the dark period than that in the light period. Increased expression of Thy-1.2 on gamma delta T cells was also observed in the light period. No significant changes were found in other subsets. This is the first report to document diurnal changes in the small intestinal IELs in mice.

Animals↗
PubMed1999

Glycoconjugate expression in follicle-associated epithelium (FAE) covering the nasal-associated lymphoid tissue (NALT) in specific pathogen-free and conventional rats.

We examined lectin-histochemically the glycoconjugate expression in the follicle-associated epithelium (FAE) covering the nasal-associated lymphoid tissue (NALT) in the rat under specific pathogen-free (SPF) and conventional (CV) conditions and compared the results for SPF and CV rats as well as for membranous (M) cells and adjacent ciliated respiratory epithelial (CRE) cells in FAE. N-acetylgalactosamine-specific lectins, Dolichos biflorus (DBA), Helix pomatia (HPA), Glycine max (SBA) and Vicia villosa (VVA), and alpha-L-fucose-specific lectin, Ulex europaeus (UEA-I), preferentially bound to M cells mainly in the luminal surface compared with CRE cells in SPF rats, whereas DBA and UEA-I showed signs of preferential binding to the apical and basolateral cytoplasm as well as to the luminal surface of M cells in CV rats. In addition, HPA, SBA and VVA more frequently and extensively labeled M cells than CRE cells in CV rats with the same subcellular staining pattern as DBA and UEA-I. On the whole, the changes in lectin binding frequency and strength were more prominent in M cells than in CRE cells in both SPF and CV rats. The present results indicate that DBA and UEA-I are useful as markers of M cells in NALT. Furthermore, the pattern of expression of carbohydrate residues recognized by such lectins in SPF and CV rats suggests that M cells are highly sensitive to environmental changes.

Animals↗
PubMed1999

Intra-articular fractures of the distal aspect of the radius: arthroscopically assisted reduction compared with open reduction and internal fixation.

BACKGROUND: There is no consensus that an arthroscopically guided operation can improve the anatomical and functional results of treatment of intra-articular fractures of the distal aspect of the radius. The purpose of the present prospective study was to determine the usefulness of arthroscopically assisted reduction of displaced intra-articular fractures of the distal aspect of the radius by comparing the results of that procedure with those of conventional open reduction and internal fixation. METHODS: Thirty-four fractures were treated with arthroscopically guided reduction with use of one volar and two dorsal arthroscopic portals. The fractures were pinned, and external fixation was used with or without autogenous bone graft. Intraoperative fluoroscopy was not used. Forty-eight fractures were treated with conventional open reduction and internal fixation with a plate and screws or with pinning, with or without external fixation. The average duration of follow-up for all fractures was thirty-one months. RESULTS: The scores for overall outcome, assessed with use of the system of Gartland and Werley and that of Green and O'Brien as modified by Cooney et al., demonstrated that the group that had had an arthroscopically assisted procedure had better outcomes than the group that had had conventional open reduction and internal fixation. The group that had had an arthroscopically assisted procedure also had significantly better ranges of flexion-extension and radial-ulnar deviation of the wrist and grip strength (p<0.05). We detected an association between the maximum step and gap displacement and evidence of osteoarthritis of the radiocarpal joint (p<0.001), but we did not find a significant association, with the numbers available, between the scores for osteoarthritis, graded according to the scale of Knirk and Jupiter, and the scores for overall outcome, assessed with the scale of Gartland and Werley and the modified system of Green and O'Brien, in either group (p = 0.376). The radiographic results showed that the patients who had had an arthroscopically assisted procedure had better reduction of volar tilt, ulnar variance, and articular (gap) displacement than did those who had been managed with conventional open reduction and internal fixation (p<0.05 for each comparison). CONCLUSIONS: An arthroscopically guided operation achieved an accurate reduction of intra-articular fractures of the distal aspect of the radius. Minimum capsular and adjacent soft-tissue scarring reduced postoperative contracture, which improved the overall functional results. We recommend arthroscopically guided reduction and internal fixation not only for young adults but for all patients who are less than seventy years old and have an intra-articular fracture of the distal part of the radius with more than one millimeter of displacement on plain radiographs.

Adolescent↗
PubMed1999

Effect of an artificial neural network on radiologists' performance in the differential diagnosis of interstitial lung disease using chest radiographs.

OBJECTIVE: We developed a new method to distinguish between various interstitial lung diseases that uses an artificial neural network. This network is based on features extracted from chest radiographs and clinical parameters. The aim of our study was to evaluate the effect of the output from the artificial neural network on radiologists' diagnostic accuracy. MATERIALS AND METHODS: The artificial neural network was designed to differentiate among 11 interstitial lung diseases using 10 clinical parameters and 16 radiologic findings. Thirty-three clinical cases (three cases for each lung disease) were selected. In the observer test, chest radiographs were viewed by eight radiologists (four attending physicians and four residents) with and without network output, which indicated the likelihood of each of the 11 possible diagnoses in each case. The radiologists' performance in distinguishing among the 11 interstitial lung diseases was evaluated by receiver operating characteristic (ROC) analysis with a continuous rating scale. RESULTS: When chest radiographs were viewed in conjunction with network output, a statistically significant improvement in diagnostic accuracy was achieved (p < .0001). The average area under the ROC curve was .826 without network output and .911 with network output. CONCLUSION: An artificial neural network can provide a useful "second opinion" to assist radiologists in the differential diagnosis of interstitial lung disease using chest radiographs.

Diagnosis, Differential↗