Biomedical subjects
Publications and source records attributed to K Katoh.
We examined the diagnosis and treatment of recurrent rectal cancer with particular regard to localized recurrence. Early diagnosis of localized recurrence is extremely important for the selection of therapeutic strategy. Among strategy options available are surgical treatment, including resection of all pelvic organs, but this should be performed with no decrease in the QOL of the patient.
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From their crystallographic comparisons, Fisher et al. (Biochemistry 34, 8960-8972, 1995) have proposed that in an important transition of myosin heads (M), M.ATP-->M.ADP.Pi, an interdomain rotation occurs in Gly468 (of chicken smooth muscle myosin) and that the rotated state is stabilized by newly-formed interdomain contacts including the salt link between Glu470 and Arg247 (of chicken smooth muscle myosin). Here, we have studied the effects of Gly468, Glu470, and Arg247 mutations on the hydrolysis of ATP. The G468A HMM did not show a significant ATPase activity, a stoichiometric initial phosphate burst, and tryptophan fluorescence enhancement attributed to bound ADP.Pi. The E470A HMM also did not show a significant ATPase activity and the phosphate burst, but the mutant gave tryptophan response attributed to bound ATP. The E470R/R247E HMM exhibited an ATPase activity and the phosphate burst which were comparable to those of the wild-type HMM, whereas neither the E470R HMM nor the R247E HMM showed such a significant ATPase activity and burst. We thus propose that both an unhindered rotation and a salt link that stabilizes the rotated state are necessary for ATP hydrolysis.
Mutations that exhibit susceptibility to acriflavine have been isolated and classified as acr mutations in Escherichia coli. We cloned the acrB gene, which has been identified as a mutation of the gyrB gene, and found a double point mutation altering two consecutive amino acids (S759R/R760C) in the COOH-terminal region of the gyrase B subunit. The mutant B subunit was found to associate with the A subunit to make the quaternary structure, and the reconstituted gyrase showed an 80-fold reduction of specific activity in DNA supercoiling assay; the sensitivity to acriflavine was not different in the same unit of wild-type and mutant gyrases. The mutant enzyme retained intrinsic ATPase activity, but DNA-dependent stimulation was observed infrequently. A gel shift assay showed that acriflavine inhibited the DNA binding of gyrase. The acrB mutation also reduced significantly the DNA binding of gyrase but did not change the sensitivity to acriflavine. These results revealed that the acrB mutation is related to the inhibitory mechanism of acriflavine; and the acriflavine sensitivity of the mutant, at least in vitro, is caused mainly by reduction of the enzyme activity. Further, our findings suggest that the COOH-terminal region of the B subunit is essential for the initial binding of gyrase to the substrate DNA.
It has been proposed from crystallographic comparisons [Fisher, A. J., Smith, C. A., Thoden, J. B., Smith, R., Sutoh, K., Holden, H. M., & Rayment, I. (1995) Biochemistry 34, 8960-8972] that in one of the important transitions of myosin head (M), M x ATP --> M x ADP x Pi, a rotation occurs in Gly468 (of chicken smooth muscle myosin). We find that mutation of this Gly to Ala does block the transition. Searching for proton acceptors in ATPase catalysis, we also find that mutation of a candidate (Glu470 of chicken smooth muscle myosin) blocks the transition. Interpretations of both findings are examined.
The phytopathogenic fungus Magnaporthe grisea has a cyanide-resistant respiratory pathway. The fungicide SSF-126 ((E)-2-methoxyimino-N-methyl-2-(2-phenoxyphenyl) acetamide) blocks the cytochrome electron transport of M. grisea and induces the alternative respiratory pathway. Twelve mutants of M. grisea more susceptible to SSF-126 than wild type were identified after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. Five mutants retained a reduced alternative respiration activity, and seven mutants lacked alternative pathway activity. A monoclonal antibody against the maize alternative oxidase cross-reacted against a 40-kDa mitochondrial protein of M. grisea, indicating that the 40-kDa protein is an alternative oxidase. Immunoblot analysis indicated that the seven completely deficient mutants grouped into two classes: four mutants produced the 40-kDa proteins while the other three mutants failed to produce the functional protein. Copyright 1997 Academic Press. Copyright 1997 Academic Press
The effects of amino acids on growth hormone (GH) release and cytosolic calcium concentration ([Ca2+]i) were investigated in caprine anterior pituitary cells cultured for 3 d in Dulbecco modified Eagle medium. The addition of an amino acid mixture consisting of seven nonessential amino acids (NEAA: L-Asp, Gly, L-Ala, L-Ser, L-Pro, L-Asn, and L-Glu; concentration of each 12.5-200 mumol/l) in the medium significantly raised GH release from the cultured cells in a concentration-dependent manner with the maximum release at 200 mumol/l NEAA. Although an addition of L-Asp (0.1-100 mumol/l) caused a significant rise in GH release in a concentration-dependent manner, neither the individual amino acids contained in NEAA except L-Asp nor others (L-Leu, L-Phe, L-Gln, L-Met, and L-Arg) caused a rise in GH release when added alone to the medium. The rise in GH release induced by NEAA (200 mumol/l) and GH-releasing hormone (GHRH, 10 nmol/l) was significantly reduced by the addition of EGTA (1.8 mmol/l) and nifedipine (1 mumol/l) to the medium, respectively. The addition of NEAA (200 mumol/l) caused a rapid and transient [Ca2+]i increase, followed thereafter by a steady increase. The prior addition of nifedipine (1 mumol/l), which itself significantly reduced the basal [Ca2+]i, completely abolished the response induced by NEAA or GHRH. From these findings, we conclude that: 1) NEAA raises GH release and [Ca2+]i in cultured caprine anterior pituitary cells, and 2) Ca2+ influx from the medium may be responsible for the cellular action of NEAA.
Of 832 acute leukemia patients, including 580 acute myeloblastic leukemia (AML), 197 pre-B acute lymphoblastic leukemia (ALL) and 55 pre-T ALL, 26 cases (3.1%) of CD13/CD33+CD7+CD19+ acute leukemia were found. A total of 20 patients were diagnosed as AML, two as pre-B ALL and four as pre-T ALL. Based on the relative intensity of expression of CD7 and CD19, CD13/CD33+CD7+CD19+ acute leukemia patients were subclassified into three categories. Type I (CD7 > CD19) included ten AML and four pre-T ALL, having cellular characteristics similar to CD7+ AML and CD13/CD33+CD7+ ALL. Type II (CD7 < CD19) consisted of four AML with t(8;21) and two pre-B ALL. Type III (CD7 = CD19) included six AML. CD13/CD33+CD7+CD19+ acute leukemia frequently expressed stem cell associated molecules, such as CD34 (88.5%), HLA-DR (96.2%) and mRNA for MDR1 (72.2%), GATA-2 (87.5%) and SCL (25.0%). Simultaneous expression of cytoplasmic CD3 and myeloperoxidase in some leukemia cells implies that CD13/CD33+CD7+CD19+ acute leukemia cells have the potential to differentiate into various lineages. These data suggest that a small population of acute leukemia patients with distinct phenotype, CD13/CD33+CD7+CD19+ acute leukemia, may originate from hematopoietic stem cells.
Expression of members of the epidermal growth factor family, including epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), amphiregulin (AR), and Cripto, as well as their putative receptor, epidermal growth factor receptor (EGFR), was studied immunohistochemically in human gastric mucosa to evaluate their possible roles in cell proliferation of normal and regenerative gastric mucosa. We also examined the correlation betwen cell proliferation and EGFR by double immunohistochemical staining for proliferating cell nuclear antigen (PCNA) and EGFR. In normal gastric mucosa, TGF-alpha, Cripto, and AR immunoreactivities were observed in the surface epithelial and parietal cells of gastric fundic glands, respectively. EGF immunoreactivity was not observed in any of normal mucosa examined. EGFR immunoreactivity was detected on foveolar cells in proliferative zones and in parietal cells. Double immunostaining revealed that EGFR immunoreactivity was distributed much more widely than PCNA immunoreactivity. PCNA positive epithelial cells adjacent to gastric ulcer margin expressed relatively intense EGFR but did not express any of the growth factors examined. On the other hand, relatively intense immunoreactivity of both TGF-alpha and Cripto was detected in PCNA-negative regenerative epithelium located distant from gastric ulcer margin. Relative immunoreactivity of AR in regenerative gastric epithelium associated with ulcer was not different from that in normal gastric mucosa. TGF-alpha, AR, and Cripto are considered to play important roles in normal gastric mucosal proliferation, and TGF-alpha and Cripto may be involved in ulcer healing, possibly via a paracrine mechanism.
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The peritrich ciliate Vorticella sp. exhibits cellular contraction of an all-or-nothing type in response to a mechanical stimulus. Many authors have suggested that the contraction may be controlled by the cytosolic level of Ca2+, since glycerol-extracted Vorticella contracts when Ca2+ is added to the external solution. However, no direct evidence for the increase in cytosolic [Ca2+] has yet been obtained in living Vorticella. In the present study, by injecting a fluorescent Ca2+ indicator into living Vorticella and monitoring the cytosolic [Ca2+] with a confocal microscope, we have demonstrated that a mechanical stimulus evoked an all-or-nothing rise in cytosolic [Ca2+] (Ca2+ 'spike'). The onset of the Ca2+ spike was similar in its time course to that of cellular contraction. Since the Ca2+ spike was recorded in a Ca2+-deprived solution containing 1 mmol l-1 EGTA, we concluded that release of Ca2+ from intracellular Ca2+ storage site(s) is responsible for the Ca2+ spike.
In measurements of jaw movements employing an X-ray television, the orientation of the patient's head must be normalized relative to the measuring device. To avoid interferring with natural jaw movements caused by using a positioning jig, we have developed an automatic head positioning system consisting of a head position sensor and a robotized chair. The position and orientation of the head is monitored by detecting the three-dimensional positions of four non-coplanar LED markers mounted on the head, by means of a set of two photoelectronic cameras. If they are incorrect, the head is moved into the required position, using a 5-degree-of-freedom robotized chair. To accomplish this accurately, the positional relations of system components must be determined precisely. This paper proposes a least-square technique of calibrating the relationship between the position sensor and the chair. Consequently, accurate positioning is achieved. Accuracy verification studies revealed that overall positioning errors lay within 2.42 mm and 1.28 degrees with respect to the position and orientation, respectively, if the markers are secured to the head support of the chair.
The occurrence of concealed infection or "natural remission" in infective endocarditis was investigated microscopically in 35 consecutive patients (36 valves) with infective endocarditis (between April 1987 and May 1995). Four patients were considered as having concealed or silent infective endocarditis. Preoperative diagnosis of these patients was mitral valve prolapse, rheumatic aortic valve stenosis with insufficiency, aortic valve prolapse and hypertrophic cardiomyopathy, respectively. These patients did not present with any clinical signs of infective endocarditis such as cardiac murmur and ventricular dysfunction. Histological examination of the excised valves revealed valvular perforation, small round cell infiltration, neovascularization, remnants of vascular smooth muscle cells, and organizing vegetations. These findings are consistent with the histological findings of infective endocarditis. Latent infective endocarditis may be present without inflammatory manifestation.
Based on the results of the Study Group for Surgical Adjuvant Radiochemotherapy for Rectal Cancer and the Study Group for Surgical Therapy and Combined Irradiation in Rectal Cancer, we examined the clinical aspects of the relatively new field of chemoradiation for rectal cancer and examined improvements in the therapeutic results. Furthermore, we examined the future outlook with particular regard to selection of therapeutic drugs and autonomic nerve preserving operation.
With a view to normalization of the head orientation without the use of a fixation jig for the measurement of jaw movement employing an X-ray television, we have been developing an automatic head-positioning system, Racs-N, consisting of a head-position sensor and a robotized chair. The head position is monitored in 6 degrees of freedom (d.o.f.) by using a position-sensitive detector (PSD) camera-based photostereometry. If they are incorrect, the robotized chair rectifies them automatically by adjusting the position and orientation of the head support in 5 d.o.f. (except the vertical position). The rectified position, however, has a certain margin of error, due to the mobility of the head relative to the head support. To improve this, we employed an iterative correction in that the positioning is repeated until the determined position converges. In experiments employing several subjects, this particular correction was verified to converge by more than six iterations and to be effective for the reduction of head-position errors.
This study was undertaken to examine the spinal cord of rats after trauma for the induction of apoptosis. DNA ladder formation was demonstrated by gel electrophoresis of the DNA obtained from the spinal cord at the site of injury after trauma from 12 h to 8 days and was most significant on Days 3 and 4. As for the longitudinal spread of the injury in the spinal cord, the ladder formation was observed in the two segments adjacent to the site of trauma 3 days after trauma. Histological examination using in situ end labeling also demonstrated the appearance of apoptosis. These results provide the evidence for the induction of apoptosis in the spinal cord after trauma in rats.
Fibronectin has been shown to bind to integrin alphaIIbbeta3 in Arg-Gly-Asp (RGD)-dependent and -independent manners. A recent study has indicated that a 29-kDa dispase-digestive fragment from the C-terminal heparin-binding domain of human plasma fibronectin (lacking RGD sequence) inhibits binding of fibronectin to thrombin-stimulated platelets and ADP-induced aggregation (Tanabe, J. , Fujita, H., Iwamatsu, A., Mohri, H., and Ohkubo, T.(1993) J. Biol. Chem. 268, 27143-27147). We provide here the evidence that a peptide corresponding to residues from Ala1704 to Glu1718 (designated F1) from this fragment inhibited binding of 125I-labeled 29-kDa fragment of fibronectin to thrombin-stimulated platelets and ADP-induced aggregation. The F1 peptide bound directly to alphaIIbbeta3 integrin receptor. These results indicate that a novel binding site in the C-terminal heparin-binding region of fibronectin is localized within the residues from Ala1704 to Glu1718. Binding of 125I-labeled 29-kDa fragment of fibronectin to thrombin-stimulated platelets was not inhibited by RGDS peptide and the 12-residue peptide from the cell-binding domain of fibronectin, suggesting that binding site in the C-terminal heparin-binding domain may be different from those of RGDS and the 12-residue peptide. This additional alphaIIbbeta3-binding domain(s) in fibronectin may also play some role for prevention of thrombus formation by direct interaction with alphaIIbbeta3.
The hematopoietic cell recognition sites of human fibronectin (FN) are the Arg-Gly-Asp-Ser (RGDS) sequence recognized by widely distributed integrin receptor alpha 5 beta 1 and the type III connecting segment (III CS) containing two cell-binding sites, designated CS1 and CS5, that are recognized by the alpha 4 beta 1 receptor. The C-terminal heparin-binding domain of FN (Hep II) has recently been demonstrated to support adhesion of alpha 4 beta 1-dependent melanoma cells [A. P. Mould and M. J. Humphries (1991) EMBO J. 10, 4089-4095]. Previously we demonstrated that this region of FN mediated binding of FN to HL-60 cells (acute promyelocytic leukemia cell line) by direct interaction independently of RGD and CS1 [H. Fujita et al., (1995) Exp. Cell Res. 217, 484-488]. In this study we have characterized a novel site in the Hep II region for binding to HL-60 cells. alpha 4 beta 1 and alpha 5 beta 1 were expressed on HL-60 cells, while alpha 2 beta 1 and alpha 3 beta 1 were not present, as shown by flow cytometry using monoclonal antibodies specific for the different integrins. Anti-alpha 4 beta 1 (P4C2) and anti-beta 1 (JB1a) antibodies inhibited binding of a 29-kDa dispase-digestive fragment of FN to HL-60 cells. This fragment contains the C-terminal heparin-binding domain of FN but lacks CS1 and CS5. Only the peptide representing the sequence from Val1866 to Arg1880, designated E1, inhibited the binding of the 29-kDa fragment to HL-60 cells. The active region of this peptide was a sequence of Thr-Asp-Ile-Asp-Ala-Pro-Ser (TAI-DAPS), which is homologous to Leu-Asp-Val-Pro-Ser (LDVPS) derived from the active site of CS1. Furthermore, labeled E1 peptide directly bound to HL-60 cells. The anti-alpha 4 beta 1 antibody (P4C2) inhibited this interaction. These results indicate that the site of binding to hematopoietic cells is present in the Hep II region of FN and the definition of the chemical structure of FN clarifies a fundamental mechanism of cell invasion of the extracellular matrix.