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Biomedical subjects

K Doi

Publications and source records attributed to K Doi.

At least 379 records · Page 21Linked to original sources
PubMed1996

Detection of the single-stranded DNA of Streptomyces plasmid pSA1.1 and a binding histone-like protein.

Streptomyces plasmid pSA1.1 accumulated single-stranded DNA as replication intermediates in S. lividans; therefore, this plasmid was considered to replicate by a rolling-circle mechanism. A DNA-binding protein (pI > 9.7 and about 10 kDa) was purified on a denatured DNA-Cellulose column, then on a native DNA-Cellulose column. The N-terminal amino acid sequence of this protein has a high homology with bacterial histone-like proteins. In the gel retardation assay, this protein bound with the single-stranded DNA of pSA1.1. We propose that this protein may participate in the replication of pSA1.1.

Amino Acid Sequence↗
PubMed1996

Excessive production of nitric oxide in rat solid tumor and its implication in rapid tumor growth.

BACKGROUND: Rapid tumor growth is caused by angiogenesis factors, growth factors, etc. We previously reported a possible connection between nitric oxide (NO) and enhanced vascular permeability in solid tumor. In the present experiment, the role of NO in solid tumor pathology was further investigated in animal tumor. METHODS: To identify NO formed in solid tumor (AH136B) implanted in the feet of rats, electron paramagnetic resonance (EPR) spectroscopy was performed directly on the frozen tumor tissue at 110K by measuring endogenous nitrosyl iron-sulfur complexes, and by using exogenously added NO capturing agents, i.e., diethyldithiocarbamate (DETC)-Fe2+ and N-(dithiocarboxy) sarcosine (DTCS)-Fe2+ complexes. Induction of inducible isoform of nosymthase iNOS mRNA was examined with reverse transcriptase-polymerase chain reaction (RT-PCR) combined with Southern blot analysis. In addition, vascular permeability was assessed by measuring extravasation of 51Cr-labeled bovine serum albumin in solid tumor. RESULTS: Strong EPR signals from NO adducts of DETC-Fe2+ and DTCS-Fe2+ as well as strong signals from NO-hemoglobin and dinitrosyl iron sulfur complex were generated by tumor. The signal height of NO-(DTCS)2-Fe2+ observed in AH136B solid tumor was increased as the tumor gained up to 1.75 g. Induction of iNOS mRNA expression was confirmed by the above methods. Enhanced vascular permeability was suppressed by NOS inhibitors N omega- monomethyl-L-arginine or S-methylisothiourea sulfate and augmented with administration of L-arginine. CONCLUSIONS: Excessive NO production by iNOS in solid tumor was identified unequivocally by EPR spectroscopy. NO formed in solid tumor can be involved in enhanced vascular permeability and increased blood flow, and hence sustain tumor growth.

Animals↗
PubMed1996

Antitumor activity of vincristine encapsulated in glucuronide-modified long-circulating liposomes in mice bearing Meth A sarcoma.

Liposomes modified with the uronic acid derivative palmityl-D-glucuronide (PGlcUA) have a long circulation time and tend to accumulate in the tumors of tumor-bearing mice. Taking advantage of this character, we investigated the therapeutic effect of vincristine (VCR) encapsulated in liposomes containing PGlcUA (dipalmitoylphosphatidylcholine/cholesterol/PGlcUA = 4:4:1 as a molar ratio) on tumor-bearing mice. VCR was loaded into liposomes by a remote loading method, and then free or liposomal VCR was injected intravenously into BALB/c mice bearing Meth A sarcoma implanted subcutaneously 5 days before hand. Single-dose administration of VCR (3.0 mg/kg) in PGlcUA-liposomes significantly suppressed tumor growth, and prolonged the survival time (T/C = 1.37). Furthermore, two-dose administration of the liposomes cured one third of the animals. The therapeutic effect of PGlcUA-liposomes was greater than that of control liposomes containing dipalmitoylphosphatidylglycerol instead of PGlcUA. PGlcUA-liposomes might thus be a useful tool for delivering antitumor agents to tumor tissues.

Animals↗
PubMed1996

Novel compliant and tissue-permeable microporous polyurethane vascular prosthesis fabricated using an excimer laser ablation technique.

A small-diameter vascular prosthesis with a multiply pored structure could have great potential to elevate the patency rate, for the following two reasons: 1) increased flexibility of the graft may increase compliance matching, consequently minimizing intimal hyperplasia; and 2) enhanced transmural tissue ingrowth may accelerate endothelialization. In this study, we fabricated a polyurethane (PU)-based artificial graft with well-controlled micropores in terms of their diameter and distribution, which was achieved using a computer-aided excimer laser (KrF) ablation technique. Three types of microporous PU tubes (2 mm in internal diameter, 100 microns in wall thickness) were designed: pore size (100 microns) and longitudinal pore-to-pore distance (200 microns) were constant, and circumferential pore-to-pore intervals were 60 degrees (type 1), 30 degrees (type 2), and 15 degrees (type 3). The fabricated prostheses were coated with photoreactive gelatin, which was photogelled and chemically fixed on PU surfaces upon ultraviolet light irradiation. Scanning electron microscopy showed that pore size and arrangement were precisely controlled as designed, and that a gelatinous hydrogel layer was formed over the entire luminal surface. The stiffness parameter (beta), inversely related to compliance, was determined from the change in external diameter against intraluminal pressure. An increase in the number of pores around the circumference decreased the beta value. The type 3 graft, the stiffness parameter of which was very close to that of human coronary artery, was the most compliant among the three types. The combination of excimer laser-directed microporing and photochemical surface processing techniques enabled the development of a novel compliant small-caliber vascular prosthesis, which is expected to show enhanced transmural tissue in growth in vivo.

Blood Vessel Prosthesis↗
PubMed1996

The effect of magnetization transfer in meniscal fibrocartilage.

Magnetic resonance imaging of the knee was performed in 28 patients (ages 15-72 years), using a 1.5-T unit. Volume gradient echo (3D GRASS) acquisition with and without presaturation off-resonance RF pulse was used to evaluate magnetization transfer (MT) effects, determined by placing regions of interest on muscle, fat, hyaline, and fibrocartilage; the percent change in signal intensity was calculated and compared using a paired two-sample t test. An in vitro study of the normal meniscus from a cadaver containing a scalpel cut extending to an articular surface was performed to observe the relative improvement in contrast in the presence of a small meniscal defect. MR imaging of the specimen was performed using an Omega CSI 2.0-T system (General Electric Medical Systems, Fremont, CA). Analysis of clinical images resulted in signal loss, compared to that of the identically timed and tuned non-MT images of 47 +/- 5, 8 +/- 5, 49 +/- 5, and 57 +/- 7% for muscle, fat, articular cartilage and fibrocartilage, respectively. Application of MT improved the depiction of the artificially introduced meniscal defect. Meniscal fibrocartilage demonstrates significant MT effect after application of off-resonance RF presaturation, which may improve visualization of meniscal defects.

Adolescent↗
PubMed1996

In vivo administration of serum thymic factor (FTS) prevents EMC-D virus-induced diabetes and myocarditis in BALB/cAJcl mice.

The effect of serum thymic factor (FTS) on the D-variant of encephalomyocarditis (EMC-D) virus-induced diabetes and myocarditis in BALB/cAJcl mice was investigated. Mice pretreated with 50 or 10 micrograms of FTS were infected with 10 or 10(3) PFU of EMC-D virus. In the mice inoculated with 10 PFU of virus, 40% developed diabetes on post-infection day (PID) 14, whereas those treated with FTS (50 micrograms/administration) on day 2 and 1 before infection did not develop diabetes. FTS (10 micrograms)-pretreated mice developed diabetes. In histological observation, FTS non-treated mice which developed diabetes showed severe necrosis and inflammation of mononuclear cells in the islets of Langerhans and myocardia on 19 PID. Mice pretreated with 50 micrograms of FTS, however, manifested mild islet degeneration without any myocardial inflammation. Furthermore, in FTS non-treated mice, immunohistological staining showed a loss of insulin granules. This loss was markedly reversed and insulin granules remained largely intact in FTS-pretreated mice. Viral titers in pancreas of FTS-pretreated mice approximated well to those of non-treated mice on PID 4, 7 and 19. In mice inoculated with higher titer of EMC-D virus (10(3) PFU), however, 50 micrograms of FTS pretreatment did not change the course of these acute pathological developments (diabetes and myocarditis observed from PID 4).

Animals↗
PubMed1996

Brain ischemia and gastric mucosal damage in spontaneously hypertensive rats: the role of arterial vagal adrenoceptors.

Brain ischemia is often accompanied by acute gastric lesions. To clarify the underlying mechanism, the influence of acute ischemic insult to the brain on gastric hemodynamics and mucosal integrity was examined in spontaneously hypertensive rats. One hour after brain ischemia, gastric mucosal blood flow decreased to 71% of the preischemic levels in the control rats but was preserved significantly better, at 94 and 108%, in the prazosin-treated and guanethidine-treated rats, respectively. Vagotomy almost abolished the decrease in gastric mucosal blood flow during cerebral ischemia. Intragastric 0.6 N hydrochloric acid administered just after reperfusion induced more severe hemorrhagic ulcers in the control than in the prazosin-treated and vagotomized groups. These results suggest that noradrenergic neurons acting through alpha1-adrenoceptors contributes to the decrease in gastric mucosal blood flow, and the subsequent disturbed integrity of the gastric mucosa, through the vagal adrenergic pathway during brain ischemia in spontaneously hypertensive rats.

Adrenergic Agents↗
PubMed1996

Quantitative analysis of geometric-pattern features of interstitial infiltrates in digital chest radiographs: preliminary results.

We are developing a computerized method for detection and characterization of interstitial diseases based on a quantitative analysis of geometric features of various infiltrate patterns in digital chest radiographs. In our approach, regions of interest (ROIs) with 128 x 128 matrix size (22.4 mm x 22.4 mm) are automatically selected, covering peripheral lung regions. Next, nodular and linear opacities, which are the basic components of interstitial infiltrates, are identified from two processed images obtained by use of a multiple-level thresholding technique and a line enhancement filter, respectively. Finally, the total area of nodular opacities and the total length of linear opacities in each ROI are determined as measures of geometric pattern features. We have applied this computer analysis to 72 ROIs with normal and abnormal patterns that were classified in advance by six chest radiologists. Preliminary results indicate that the distribution of measures of geometric-pattern features correlate well with radiologists' classification. These early results are encouraging, and further evaluation hopes to establish that this computerized method might prove useful to radiologists in their assessment of interstitial diseases.

Humans↗
PubMed1996

Apoptosis in the aged dog brain.

Apoptosis similar to that seen in Alzheimer's disease patients was found in the brain of aged dogs by the TUNEL method of detecting in situ DNA fragmentation. Apoptosis was observed in both neurons and glial cells, and was morphologically characterized by round and swollen cytoplasm and aggregated nuclear chromatin, although these changes were slight. Neurons and astrocytes in the gray matter and oligodendrocytes in the white matter were affected. The number of ApopTag-positive brain cells increased slightly with age, but was not correlated to the number of senile plaques. A good correlation between the number of ApopTag-positive cells and the dementia index was clearly found. The present study indicates that brain cell apoptosis could account for dementia in aged dogs and suggested that aged dogs may be useful as a simplified animal model for Alzheimer's disease in man.

Aging↗
PubMed1996

Restoration of sensibility in the hand after complete brachial plexus injury.

Twenty-one patients with complete brachial plexus palsy due to the avulsion of multiple cervical nerve roots underwent motor and sensory reconstruction. Of these, 15 patients who had been followed for at least 2 years were included in the present study. Sensory reconstruction was performed by nerve graft or nerve crossing to the median nerve. The donor nerves included the supraclavicular nerve in 10 patients, the intercostal nerve in 3, and the C5 nerve root in the first 2 patients. Limited sensibility in the median nerve distribution of the hand was restored in 12 patients, and the results were classified as S2+ in 2, S2 in 4, S1 in 6, and S0 in 3, according to the S0 to S4 grading system. No moving two-point discrimination was restored in any case. While the best recovery obtained was only at the S2+ level, even this limited sensibility was useful for otherwise completely anesthetic patients.

Adolescent↗
PubMed1996

An improved computer-assisted diagnostic scheme using wavelet transform for detecting clustered microcalcifications in digital mammograms.

RATIONALE AND OBJECTIVES: We evaluated the potential usefulness of a computer-assisted diagnostic (CAD) scheme incorporating the wavelet transform for detecting clustered microcalcifications in mammograms. METHODS: A wavelet transform technique was applied to the detection of clustered microcalcifications. We examined several wavelets to study their effectiveness in detecting subtle microcalcifications. We used a database consisting of 39 mammograms containing 41 clusters of microcalcifications. The performance of the wavelet-based CAD scheme was evaluated using free-response receiver operating characteristic analysis. RESULTS: The CAD scheme with the wavelet transform was useful in detecting some of the subtle microcalcifications that were not detected by our previous scheme, which was based on the difference-image technique. When the two schemes were combined, the overall performance was improved to a sensitivity of approximately 95%, with a false-positive rate of 1.5 clusters per image. CONCLUSION: The wavelet transform approach can improve the detection of subtle clustered microcalcifications.

Calcinosis↗
PubMed1996

Relation between distribution of viral RNA and development of histopathological changes in encephalomyocarditis virus-induced orchitis in mice.

The relation between the distribution of viral RNA and the development of histopathological changes was investigated in the early stage of encephalomyocarditis (EMC) virus-induced orchitis in mice. Signals of viral RNA were first detected by in situ hybridization in a few Sertoli cells in almost intact germinal epithelia at 2 days post-inoculation (d.p.i.). The number of Sertoli cells bearing signals of viral RNA increased at 3 d.p.i. when mild degenerative changes were exceptionally found in germinal epithelia. Signals of viral RNA came to be detected not only in Sertoli cells but also in a small number of germinal cells and spermatogonia at 4 d.p.i. when mild to moderate degenerative changes developed in germinal epithelia, resulting in desquamation of degenerated cells. At the same time, virus-like particles were observed by electron-microscopy in the degenerated and desquamated germinal cells. At and after 5 d.p.i., luminal obstruction with cellular debris and inflammatory cells was generally found. These results suggest that EMC virus carried to seminiferous tubules via the blood first attacks Sertoli cells and then damages germinal cells and spermatogonia.

Animals↗
PubMed1996

Depletion of Mac1-positive macrophages protects DBA/2 mice from encephalomyocarditis virus-induced myocarditis and diabetes.

DBA/2 mice treated with anti-Mac1 monoclonal antibody (MAb) failed to develop encephalomyocarditis virus (EMCV)-induced diabetes and myocarditis. Virus concentrations and the number of viral RNA-positive cells in the pancreas and heart were significantly reduced in mice treated with anti-Mac1 MAb. Mac1-positive macrophages seem to be involved in EMCV-induced disease and to affect the replication of EMCV in target organs.

Animals↗
PubMed1996

Congenital mediastinal bronchogenic cyst with malignant transformation: an autopsy report.

A rare autopsy case of mediastinal bronchogenic cyst with malignant transformation is presented. The cyst had been located in the anterior mediastinum for at least 28 years in a 52 year old male. Chest X-ray findings showing rapid enlargement of the cyst and biopsy of the spine for lumbago made a clinical diagnosis as suspicious mediastinal cystic teratoma with malignant transformation metastasizing to the spine. Postmortem examination revealed that the cyst was located in the anterior mediastinum extending to the left pulmonary hilum and had no connection with the tracheobronchial tree. The cyst wall consisted of bronchus-like tissue including ciliated epithelium, hyaline cartilage, smooth muscle and mucoserous glands. There were no teratomatous components in the wall. Malignant tumor predominantly consisting of round cells occurred in the thickened cyst wall and grew into the cyst cavity with direct invasion of the lung and metastases to the liver, adrenal glands, bone marrow of the lumbar spine and lymph nodes. An immunohistochemical study showed that the tumor cells frequently expressed cytokeratin, epithelial membrane antigen and carcino-embryonic antigen, occasionally CA19-9, vimentin and neuron-specific enolase. From these findings, the tumor was diagnosed as undifferentiated carcinoma arising in the mediastinal bronchogenic cyst.

Bronchogenic Cyst↗
PubMed1996

Immunohistochemical characteristics of the constituents of senile plaques and amyloid angiopathy in aged cynomolgus monkeys.

In this study, we immunohistochemically examined the several constituents of senile plaques (SPs) and cerebral amyloid angiopathy (CAA) in aged cynomolgus monkeys. Apolipoprotein E (apoE) deposited in all mature plaques and CAA, and in half of the diffuse plaques. Alpha-1-antichymotripsin (alpha ACT) deposited in half of the mature plaques and in one third of the CAA. Amyloid precursor protein (APP), ubiquitin (Ub), and microtubule-associated protein-2 (MAP-2) accumulated in the swollen neurites of mature plaques. Glial fibrillary acidic protein (GFAP) was detected in the astrocytes and their processes surrounding the mature plaques. Tau was detected in neither the SPs nor CAA. Therefore, mature plaques involved extracellular A beta, apoE, and alpha ACT, and also astrocytes and swollen neurites. However, diffuse plaques involved only extracellular A beta and apoE. Since these features, except for tau, were consistent with those in humans, this animal model will be useful for studying the pathogenesis of cerebral amyloid deposition.

Aging↗
PubMed1996

Image feature analysis for computer-aided diagnosis: detection of right and left hemidiaphragm edges and delineation of lung field in chest radiographs.

Diaphragm edges, together with ribcage edges, in chest radiographs provide useful information on the location, shape, and size of the lung fields that are required by computer-aided diagnosis (CAD) schemes for automated detection of various abnormalities. In this continued study, we developed a computerized method for detection of the right and left hemidiaphragm edges. First, the right hemidiaphragm edges in a PA (postero-anterior) chest image were determined by edge gradient analysis. An initial vertical ROI was then placed at the middle of the left hemidiaphragm, based on a "standard rule" for determination of the starting points to search for the left hemidiaphragm edges. Seven categories were used to assess the accuracy of the placement of the initial ROI and the selection of the primary left starting point within the initial ROI. For some categories, it was necessary to select a second left starting point besides the primary one. Therefore, for these categories, two sets of "detected left hemidiaphragm edges" resulted from the two left starting points. Two parameters were used as measures to eliminate the false left hemidiaphragm edges which were due to an incorrect left starting point. Two polynomial functions were applied separately which produced smooth curves for the right and left hemidiaphragm edges. Finally, the delineation of the lung field in a chest image was obtained by connecting the right and left hemidiaphragm edge curves with the corresponding ribcage edge curves. The subjective evaluation results indicated that the accuracy for the determination of the right and left hemidiaphragm edges was approximately 97% and 90%, respectively.

Biophysical Phenomena↗
PubMed1996

The effect of x-ray beam alignment on the performance of antiscatter grids.

While the qualitative effects of grid misalignment are known, we have quantified the effect of different degrees of grid misalignment on image contrast and patient exposure. Radiographs were made of a phantom consisting of five lead disks on top of a 15 cm block of lucite. Four 60 lines/cm grids, having grid ratios of 3:1, 4:1, 6:1, and 8:1 were used. When the tube was angled more than three degrees across the grid lines, the contrast improvement factor decreased substantially for all four grids, as much as 46% for an 8:1 grid with a 12 degrees misalignment. There was a concomitant decrease in film optical density, which if compensated for by an increase in patient exposure, would lead to a higher effective bucky factor. With the exception of the 3:1 grid, if the grid is misaligned by more than 6 degrees, higher signal-to-noise ratios can be attained by removing the grid and using the increased patient exposure to reduce noise.

Colloids↗