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K Doi

Publications and source records attributed to K Doi.

At least 469 records · Page 26Linked to original sources
PubMed1994

Therapeutic effect of adriamycin encapsulated in long-circulating liposomes on Meth-A-sarcoma-bearing mice.

Long-circulating liposomes modified with a uronic-acid derivative, palmityl-D-glucuronide (PGIcUA), have been developed previously for the passive targeting of liposomes to tumor tissues. In this study, we examined the therapeutic effect of adriamycin (ADM) encapsulated in PGIcUA liposomes composed of dipalmitoylphosphatidylcholine (DPPC), cholesterol (Chol) and PGIcUA (molar ratio, 40/40/10) since this amount of PGIcUA was enough to endow liposomes with long-circulating activity. Long-circulating activity was also observed with palmityl-D-galacturonide (PGalUA) modified liposomes, suggesting that uronic acid plays an important role in preventing liposomes from being trapped in the reticuloendothelial system (RES). ADM was loaded in liposomes by a remote-loading method. Free or liposomal ADM was injected i.v. into BALB/c mice bearing s.c.-implanted Meth-A sarcoma. The liposomal formulation was efficient for reducing tumors, prolonging survival time and curing the animals, especially in the case of large tumors where free ADM was not. Furthermore, PGlcUA liposomes were more effective than conventional liposomes containing dipalmitoylphosphatidylglycerol (DPPG) instead of PGlcUA for prolonging survival time in mice. It might therefore be appropriate to use PGlcUA liposomes as the carriers of anticancer drugs.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Existence of an enzymatic pathway furnishing arachidonic acid for prostaglandin synthesis from arachidonoyl CoA in rabbit kidney medulla.

We examined whether arachidonoyl CoA (AA-CoA) can be a possible supplier of arachidonic acid (AA) for prostaglandin (PG) synthesis in rabbit kidney medulla. AA-CoA was preincubated with or without the 105,000 g supernatant (cytosol) fraction from the kidney medulla for 5 min at 37 degrees C followed by the incubation with the microsomal fraction (0.5 mg protein) (a rich source of PG synthesizing enzymes) in the presence of reduced glutathione and hydroquinone for 5 min at 37 degrees C, and the formed PGE2, F2 alpha and D2 were measured by high-pressure liquid chromatography using 9-anthryldiazomethane for derivatization. The addition of AA-CoA (20 nmol) alone changed the total PG formation (the sum of PGE2, F2 alpha and D2) from 0.14 to 1.55 ng. When the cytosolic fraction (10-100 microliters) was added together with 20 nmol-AA-CoA in the preincubation mixture, total PG formation was further increased 2- to 3-fold compared to AA-CoA alone. Experiments utilizing AA, instead of AA-CoA and boiled cytosolic fraction revealed that the stimulatory action of the cytosolic fraction on the AA-CoA-induced PG synthesis may not be due to the effect on cyclooxygenase activity and due to long-chain acyl CoA hydrolase. These results show that long-chain acyl CoA hydrolase which hydrolyzes AA-CoA to AA is present in the cytosol of rabbit kidney medulla and suggest that this enzyme activity is a potential mediator of supply of AA for PG synthesis in this region.

Acyl Coenzyme A↗
PubMed1994

A deletion in the second cytoplasmic loop of GluR3 produces a dominant negative mutant of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor.

We have characterized a GluR3 mutant (sGluR3) which has a 33-amino acid deletion in its second cytoplasmic loop (deficit from Tyr-715 to Gly-747 of GluR3-flop). Xenopus oocytes injected with cRNA transcribed from cDNA for this mutant did not respond to kainate and glutamate (each 100 microM) at a holding potential of -70 mV. In oocytes coinjected with cRNAs for this mutant and for normal alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunits, the current response to both kainate and glutamate was much weaker than that observed in oocytes injected with cRNA for the normal subunits alone. This inhibitory action was not accompanied by a significant change of ED50 value and shape of the I-V curve and was AMPA receptor-specific. A comparable deletion in GluR1 produced a mutant with properties similar to those of sGluR3, while a 33-amino acid deletion elsewhere in the second cytoplasmic loop of GluR3 (Met-674 to Phe-706) gave a mutant with a weaker effect. These results suggest that sGluR3 acts as a dominant negative mutant on the functional expression of normal AMPA receptors in oocytes by assembling with the normal subunits to produce an essentially nonfunctional receptor complex.

Amino Acid Sequence↗
PubMed1994

Potential usage of thermosensitive liposomes for macromolecule delivery.

Since transient swelling during phase transition of liposomes with hyper-osmotic internal aqueous phase may cause permeation of large molecules through the lipid bilayer, this type of liposomes can be useful for delivering macromolecules. In fact, thermosensitive liposomes containing an internal solution with osmotic pressure 2-fold higher than the physiologic level and sized through 200-nm pore, released encapsulated macromolecules such as dextran (M(r) 144,000) effectively when they were incubated at 40-42 degrees C. These liposomes were stable in the presence of serum compared to the liposomes with internal osmotic pressure more than 3-fold higher than the physiologic level.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

[Preliminary clinical evaluation of computer-aided diagnosis in digital chest radiography].

We are developing computer-aided diagnosis (CAD) schemes for chest radiography with which to alert radiologists to possible lesions, and thus potentially improve diagnostic accuracy. Although preliminary results of individual CAD schemes have been encouraging, CAD is still at an early stage of its development. Therefore, we applied our CAD programs in a clinical environment and evaluated its potential usefulness and limitations. CAD programs including automated detection of cardiomegaly, analysis of interstitial infiltrates, and detection of lung nodules were applied to 310 consecutive chest radiographs. CAD results for cardiomegaly and interstitial infiltrates were evaluated subjectively by radiologists and physicists for clinical accuracy and technical problems, respectively, depending on the correspondence of the CAD output to the nature and location of important findings influencing the radiologic diagnosis. CAD results for lung nodules were evaluated objectively by taking into account the number of false positives and true positives. For detection of cardiomegaly, 71% of evaluated cases were judged to be acceptably accurate in terms of clinical accuracy. For analysis of focal and diffuse interstitial infiltrates, 87% and 61% were acceptably accurate, respectively. For detection of lung nodules, 61% were acceptably accurate. More than 70% of CAD output was judged to be possibly accurate in terms of technical aspects. Technical problems were related to failure to detect subtle abnormalities and the occurrence of false positives caused by normal anatomical structures. We believe that CAD has the potential to be a valuable aid for radiologists in clinical practice, if certain technical problems can be overcome and if optimal operating points can be defined for clinical use.

Diagnosis, Computer-Assisted↗
PubMed1994

MSG5, a novel protein phosphatase promotes adaptation to pheromone response in S. cerevisiae.

Pheromone-stimulated yeast cells and haploid gpa1 deletion mutants arrest their cell cycle in G1. Overexpression of a novel gene called MSG5 suppresses this inhibition of cell division. Loss of MSG5 function leads to a diminished adaptive response to pheromone. Genetic analysis indicates that MSG5 acts at a stage where the protein kinases STE7 and FUS3 function to transmit the pheromone-induced signal. Since loss of MSG5 function causes an increase in FUS3 enzyme activity but not STE7 activity, we propose that MSG5 impinges on the pathway at FUS3. Sequence analysis suggests that MSG5 encodes a protein tyrosine phosphatase. This is supported by the finding that recombinant MSG5 has phosphatase activity in vitro and is able to inactivate autophosphorylated FUS3. Thus MSG5 might stimulate recovery from pheromone by regulating the phosphorylation state of FUS3.

Adaptation, Physiological↗
PubMed1994

Vascularized periosteal bone graft from the supracondylar region of the femur.

Free, vascularized thin corticoperiosteal grafts and small periosteal bone grafts harvested from the supracondylar region of the femur are described. These grafts are nourished from the articular branch of the descending genicular artery and vein. Thin corticoperiosteal grafts consist of periosteum with a thin layer of outer cortical bone and include the cambium layer, which has a better osteogenic capacity. This graft is elastic and readily conforms to the recipient bed configuration. Thin corticoperiosteal grafts were used to treat 11 patients with fracture non-union of an upper extremity that had no massive bone defects. Early, rapid union occurred in all patients except three: one in which the anastomosed vessel became obstructed and two in which the internal fixation of the fracture was unsecured. The small bone grafts consist of periosteum, full thickness cortex, and the underlying cancellous bone. This graft can be successfully harvested without disturbing the vascularity, unlike the currently used vascularized bone grafts. This graft was used to treat three patients with avascular necrosis of the body of the talus and could prevent the necrotic talus body from progressive collapse in patients in early stages of the disease. One patient with an infectious bone defect of the first metatarsal bone was successfully treated by vascularized bone graft with an accompanying skin flap.

Adolescent↗
PubMed1994

Experimental study on vascularized bone allografts for reconstruction of massive bone defects.

To study the healing mechanism of vascularized bone allografts under short-term as well as long-term immunosuppression with cyclosporin A, experimental vascularized intercalary bone allograft transplantation was carried out between inbred rats using the tibiofibula graft model. Bone scintigram and radiographs were used as an indicator for early detection of rejection after transplantation and bone union. In vascularized bone allografts under long-term immunosuppression with cyclosporin A, early bone union and continuous incorporation were similar to that observed in vascularized bone autograft transplantation. When administration of cyclosporin A was discontinued before completion of bone union, the graft was rejected and bone union was delayed. Apparent swelling on the operated limb associated with a decrease in bone scintigram uptake suggested the occurrence of rejection of the allograft. Vascularized bone allograft transplantation is useful for reconstruction of massive bone defects only if immunosuppressants are used and maintained at least until bone union is obtained.

Animals↗
PubMed1994

Vascularized bone allografts: review of current concepts.

Advances in the field of microsurgery over the past two decades, together with the discovery of a powerful immunosuppressive, cyclosporin A, have brought vascularized osteochondral allografts closer to reality. In this review, the authors describe the history of laboratory research on vascularized osteochondral allografts using immunosuppression, as well as their experimental and preliminary clinical experiences.

Animals↗
PubMed1994

Detection of liver fibrosis with magnetic cross-relaxation.

The utility of MRI using magnetization transfer (MT) enhanced pulse sequences to diagnose hepatic cirrhosis in a rat model was investigated. Hepatic T1 was measured with and without MT off-resonance RF pulses in 17 treated and six control rats. The livers were evaluated histologically, and the hydroxyproline content quantitatively measured. We did not find a statistically significant linear correlation between the MR relaxation times and the degree of tissue injury. However, the MR measurements performed with MT were superior to those without differentiating the treated and control groups. Specifically, the T1 times were 695 +/- 76 ms for the treated group, versus 748 +/- 61 ms in the controls; P = 0.095. The T1sat times were also lower in the treated group, with statistical significance: 367 +/- 51 ms versus 421 +/- 38 ms, P = 0.016. Finally, the change in the relaxation rates (the inverse of the relaxation times) with and without saturation were 1.31 +/- 0.22 s-1 (treated group) versus 1.05 +/- 0.12 s-1 (controls), which differed significantly, P = 0.001.

Animals↗
PubMed1994

Protective effects of sulfhydryl compounds on HOCl-induced intracellular Ca2+ increase in single rat ventricular myocytes.

Effects of sulfhydryl compounds on cell injuries caused by hypochlorous acid (HOCl) were studied in isolated rat cardiomyocytes by way of continuous measurement of intracellular Ca2+ using calcium sensitive fluorescent dye, fura-2. Ten minutes exposure of the cell to 100 microM HOCl induced a significant increase in the intracellular free calcium concentration ([Ca2+]i) from 90 +/- 20 nM to 266 +/- 74 nM (n = 44, mean +/- S.D.). This increase in [Ca2+]i was reversed by subsequent application of dithiothreitol (DTT) in a dose dependent manner; 30 microM DTT was found effective, while 2 mM DTT almost completely restored the [Ca2+]i to the control level. Similar to DTT, cysteine ethyl ester and cysteine methyl ester could also reverse the HOCl-induced rise of [Ca2+]i where the order of the potency was DTT > cysteine ethyl ester > cysteine methyl ester. In contrast, increase in [Ca2+]i induced by HOCl was not recovered by application of other sulfhydryl compounds such as cysteine and glutathione. Since HOCl administrated in the presence of cysteine failed to induce an increase in [Ca2+]i, we conclude that membrane permeable sulfhydryl compounds may reverse the increase in [Ca2+]i caused by HOCl.

Animals↗
PubMed1994

Overexpression of the Saccharomyces cerevisiae MET17/MET25 gene in Escherichia coli and comparative characterization of the product with O-acetylserine.O-acetylhomoserine sulfhydrylase of the yeast.

The Saccharomyces cerevisiae MET17/MET25 gene encoding O-acetyl-L-serine (OAS).O-acetyl-L-homoserine (OAH) sulfhydrylase (EC 4.2.99.10) was overexpressed in Escherichia coli and the gene product was purified to homogeneity, using three steps, with a recovery of 28% from the total cell extract. The gene product has been compared with OAS.OAH sulfhydrylase purified from the yeast cells. These two protein preparations were indistinguishable with respect to their behavior in polyacrylamide gel electrophoresis, both with and without sodium dodecyl sulfate, their specificity for substrate amino acids, Michaelis constant (Km) value for OAH, sensitivity to carbonyl reagents, absorption spectrum, isoelectric point, behavior in HPLC (both ion-exchange chromatography and gel filtration), sensitivity to heat treatment, susceptibility to trypsin digestion, and their N-terminal amino acid sequence. The results obtained imply that the gene product is properly processed in E. coli, and the technique developed in this study to overexpress the gene in bacterial cells provides us with a large amount of the purified preparation of the enzyme. In contrast to a previous report we found that cystathionine gamma-lyase of S.

Amino Acid Sequence↗
PubMed1994

Computerized detection of masses in digital mammograms: investigation of feature-analysis techniques.

Mammographic screening of asymptomatic women has shown effectiveness in the reduction of breast cancer mortality. We are developing a computerized scheme for the detection of mammographic masses as an aid to radiologists in mammographic screening programs. Possible masses on digitized screen/film mammograms are initially identified using a nonlinear bilateral-subtraction technique, which is based on asymmetric density patterns occurring in corresponding portions of right and left mammograms. In this study, we analyze the characteristics of actual masses and nonmass detections to develop feature-analysis techniques with which to reduce the number of nonmass (ie, false-positive) detections. These feature-analysis techniques involve (1) the extraction of various features (such as area, contrast, circularity and border-distance based on the density and geometric information of masses in both processed, and original breast images), and (2) tests of the extracted features to reduce nonmass detections. Cumulative histograms of both actual-mass detections and nonmass detections are used to characterize extracted features and to determine the cutoff values used in the feature tests. The effectiveness of the feature-analysis techniques is evaluated in combination with the computerized detection scheme that uses the nonlinear bilateral-subtraction technique using free-response receiver operating characteristic analysis and 77 patient cases (308 mammograms). Results show that the feature-analysis techniques effectively improve the performance of the computerized detection scheme: about 35% false-positive detections were eliminated without loss in sensitivity when the feature-analysis techniques were used.

Breast Neoplasms↗
PubMed1994

Development of a digital duplication system for portable chest radiographs.

To provide high-quality duplicate chest images for the intensive care units, we have developed a digital duplication system in which film digitization is performed in conjunction with nonlinear density correction, contrast adjustment, and unsharp mask filtering. This system provides consistent image densities over a wide exposure range and enhancement of structures in the mediastinum and upper abdominal areas, improving visibility of catheters and tubes. The image quality is often superior to that of the original radiograph and is more consistent from day to day. Repeat rates for portable chest radiographs have been reduced by more than a factor of two since implementation of digitization in December 1991, and the number of repeat examinations caused by exposure errors have been substantially reduced.

Computer Systems↗
PubMed1994

Reduction of false positives in computerized detection of lung nodules in chest radiographs using artificial neural networks, discriminant analysis, and a rule-based scheme.

A computer-aided diagnosis (CAD) scheme is being developed to identify image regions considered suspicious for lung nodules in chest radiographs to assist radiologists in making correct diagnoses. Automated classifiers--an artificial neural network, discriminant analysis, and a rule-based scheme--are used to reduce the number of false-positive detections of the CAD scheme. The CAD scheme first detects nodule candidates from chest radiographs based on a difference image technique. Nine image features characterizing nodules are extracted automatically for each of the nodule candidates. The extracted image features are then used as input data to the classifiers for distinguishing actual nodules from the false-positive detections. The performances of the classifiers are evaluated by receiver-operating characteristic analysis. On the basis of the database of 30 normal and 30 abnormal chest images, the neural network achieves an AZ value (area under the receiver-operating-characteristic curve) of 0.79 in detecting lung nodules, as tested by the round-robin method. The neural network, after being trained with a training database, is able to eliminate more than 83% of the false-positive detections reported by the CAD scheme. Moreover, the combination of the trained neural network and a rule-based scheme eliminates 96% of the false-positive detections of the CAD scheme.

Diagnosis, Computer-Assisted↗
PubMed1994

Glycolysis vs. respiration as ATP source for the shape of quiescent cardiomyocytes.

ATP concentration ([ATP]) and the fraction of rod-shaped myocytes (Rrod) were measured for quiescent ventricular cells isolated from the rat heart. The myocytes were gently shaken with metabolic inhibitors for 30 min at 37 degrees C, and then [ATP] was assayed enzymatically. [ATP] (mean +/- SE in nmol.(10(6) cells)-1) of the control group (80.2 +/- 6.3) was significantly reduced to 32.3 +/- 3.6 and 21.9 +/- 4.5 by inhibiting glycolysis with 2-deoxyglucose (DG, 10 mM) and iodoacetic acid (IAA, 2 mM), respectively. Inhibition of the oxidative phosphorylation by sodium cyanide (CN, 2 mM) or 2,4-dinitrophenol (DNP, 40 microM) did not induce significant [ATP] reduction (56.5 +/- 5.6 or 53.2 +/- 7.5). Rrod were 54.4 +/- 1.9, 47.3 +/- 5.1, 43.3 +/- 3.3, 28.5 +/- 3.6 and 11.6 +/- 1.8% for the control, CN, DNP, DG and IAA groups, respectively. Under glycolytic inhibition with DG, addition of pyruvate (5 mM) with a pyruvate dehydrogenase activator (dichloroacetate (DCA, 1 mM) or (-)isoproterenol (ISO, 10 microM)) restored [ATP] to 52.5 +/- 8.3 and 67.7 +/- 7.2, respectively, but Rrod still remained depressed (34.6 +/- 2.1 and 35.4 +/- 1.3%). We conclude that the normal shape of quiescent myocytes is maintained primarily by glycolytic ATP.

2,4-Dinitrophenol↗