MI Aguilar  DJ Clayton  P Holt  V Kronina  RI Boysen  AW Purcell  MT Hearn 《Canadian Metallurgical Quarterly》1998,70(23):5010-5018

Procedures have been developed to identify the chromatographic binding domains of horse heart cytochrome c (Cyt c) and bovine growth hormone (bGH) during their interaction with reversed-phase sorbent materials. The procedure involves adsorption of the protein solute to the chromatographic sorbent, followed by proteolytic cleavage. Comparison of the proteolytic map obtained for Cyt c and bGH in free solution with the corresponding map obtained when these proteins are adsorbed to the chromatographic sorbent revealed significant differences in the digestion pattern. Following characterization of the peptides generated in both maps, the results indicated that specific regions on the surface of both Cyt c and bGH are inaccessible to tryptic cleavage when adsorbed to the hydrophobic surface of both a C-4 and a C-18 sorbent. Based on the assumption that the region of the protein surface that is in contact with the sorbent remains intact and bound to the sorbent during the digestion step, while the protein surface that is exposed to the solvent is accessible to proteolysis, the regions that were inaccessible to tryptic digestion were found to correspond to hydrophobic domains on the protein surface. These results also suggest that the three-dimensional structures of these proteins remain largely intact upon adsorption to the hydrophobic surface.  相似文献   

    

DJ Anh  HP Dimai  SL Hall  JR Farley 《Canadian Metallurgical Quarterly》1998,62(4):332-340

Low-affinity penicillin-binding proteins (PBPs), which participate in the beta-lactam resistance of several pathogenic bacteria, have different origins. Natural transformation and recombination events with DNA acquired from neighbouring intrinsically resistant organisms are responsible for the appearance of mosaic genes encoding two or three low-affinity PBPs in highly resistant strains of transformable microorganisms such as Neisseria and Streptococcus pneumoniae. Methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococcal strains possess the mecA determinant gene, which probably evolved within the Staphylococcus genus from a closely related and physiologically functional gene that was modified by point mutations. The expression of mecA is either inducible or constitutive. A stable high-level resistant phenotype requires the synthesis of a normally constituted peptidoglycan. Enterococci have a natural low susceptibility to beta-lactams related to the presence of an intrinsic low-affinity PBP. Highly resistant enterococcal strains overexpress this PBP and/or reduce its affinity.  相似文献   

    

LJ Lombardi  DJ Cleri  BC Horten  CA LaMarca  RN Holtzman 《Canadian Metallurgical Quarterly》1995,24(7):553-557

A synovial sarcoma (SS) is an uncommon malignant soft-tissue tumor, which in spite of its name does not arise from synovial tissue. It is so named because of its histologic similarity to synovium. An SS originates from mesenchyme, not from synoviocytes and usually manifests as a biphasic tumor with both malignant-epithelial and spindle-cell components. Monophasic epithelial and spindle-cell presentations may cause a diagnostic dilemma. Diagnosis should include immunocytochemistry using cytokeratin and/or epithelial membrane antigen; vimentin further helps to eliminate any histologic confusion. These tumors are most commonly found in the extremities. When located near a joint, invasion occurs only by secondary extension. Rarely are SSs found in the neck, especially in the posterior aspect, as reported here.  相似文献   

    

MF Vineyard  SE Atencio  JF Crum  GP Gilfoyle  BG Glagola  DJ Henderson  DG Kovar  CF Maguire  JF Mateja  RG Ohl  FW Prosser  JH Rollinson  RS Trotter 《Canadian Metallurgical Quarterly》1994,49(2):948-954

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TM Ryan  DJ Ciavatta  TM Townes 《Canadian Metallurgical Quarterly》1997,278(5339):873-876

When transgenic mice that expressed human sickle hemoglobin were mated with mice having knockout mutations of the mouse alpha- and beta-globin genes, animals were produced that synthesized only human hemoglobin in adult red blood cells. Similar to many human patients with sickle cell disease, the mice developed a severe hemolytic anemia and extensive organ pathology. Numerous sickled erythrocytes were observed in peripheral blood. Although chronically anemic, most animals survived for 2 to 9 months and were fertile. Drug and genetic therapies can now be tested in this mouse model of sickle cell disease.  相似文献   

    

JR Beach  JH Dennis  AJ Avery  CL Bromly  RJ Ward  EH Walters  SC Stenton  DJ Hendrick 《Canadian Metallurgical Quarterly》1996,154(5):1394-1400

To clarify whether asthma may be caused by fume from welding mild steel and to evaluate the possible strength of such an effect, we quantified airway responsiveness among young shipyard workers with different levels of fume exposure. Clinical investigation comprised a cross-sectional survey of 19- to 27-yr-old workers who were completing 3 to 9 yr of employment in various trades, and a control group of 15- to 17-yr-old school leavers who were applying for apprenticeships within the same trades. Both groups were subdivided into negligible-, ambient-, or high-exposure subgroups according to expected levels of fume exposure. Actual exposures were assessed in a parallel environmental survey. Participants were investigated by questionnaire, skin prick tests, spirometry, and methacholine tests. Complete data sets were obtained from 1,024 of the 1,070 eligible subjects (96%). Among the workers but not the school leaver controls, there was an increasing prevalence of positive methacholine tests across the exposure subgroups-negligible 37%, ambient 44%, high 49% (p < 0.05). Regression analyses showed that in males after allowing for the effects of atopy, current smoking, and age, the estimated geometric mean level of airway responsiveness of regular welders was twice that of workers with negligible exposure after 5 yr of work. This implies that fume exposure may have been critical in causing asthma in about 1% of the welders. A lesser effect (though not significantly so) was noted among the workers with ambient exposure.  相似文献   

    

AW Sandvik  DJ Scalapino 《Canadian Metallurgical Quarterly》1996,53(2):R526-R529

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DJ Wolff  A Lubeskie 《Canadian Metallurgical Quarterly》1996,325(2):227-234

We studied the value of long video-split electroencephalographic monitoring (VSEEG) in detecting myoclonus in nearly SSPE and evaluated the natural history and outcome-affecting factors. The 32 newly diagnosed patients had VSEEG to detect myoclonus and its correlations with EEG periodic complexes. Disease progression was monitored by a special \"outcome score'; the chi-square test and multi-variable statistics analysed the outcome score in relation to different variables, such as age at onset, sex, duration of symptoms at presentation, CSF measles antibody titre, type and interval between periodic complexes (EEG discharges). Myoclonus or atonia occurred in all patients and was time-related to the EEG periodic complexes; in 32% of patients, myoclonus or atonia were not clinically evident. The EEG periodic complexes were of 3 types: Type I (16 patients) periodic giant delta waves; Type II (10 patients) periodic giant delta waves intermixed with rapid spikes or fast activity; and Type III (6 patients), long spike-wave discharges interrupted by giant delta waves. Outcome score was associated with symptoms duration (P < 0.01) and EEG periodic complexes (P < 0.05). Symptom duration was inversely related to final outcome (multi-variable analysis). Long VSEEG monitoring greatly improves early diagnosis and detection of subtle atonia or segmental myoclonus. Prognostic factors were the type of EEG periodic complexes and duration of symptoms at presentation.  相似文献   

    

R Lacey  NN Ajitanand  JM Alexander  de Castro Rizzo DM  GF Peaslee  LC Vaz  M Kaplan  M Kildir  La Rana G  DJ Moses  WE Parker  D Logan  MS Zisman  P DeYoung  L Kowalski 《Canadian Metallurgical Quarterly》1988,37(6):2561-2577

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TE Carver  DJ Sexton  SJ Benkovic 《Canadian Metallurgical Quarterly》1997,36(47):14409-14417

The mechanism of bacteriophage T4 DNA polymerase (gp43) and clamp (gp45) protein dissociation from the holoenzyme DNA complex was investigated under conditions simulating the environment encountered upon completion of an Okazaki fragment. Lagging strand DNA synthesis was approximated using a synthetic construct comprised of a doubly biotinylated, streptavidin-bound 62-mer DNA template, paired with complementary primers to generate an internal 12-base gap where the 5'-end primer contained either a 5'-OH (DNA primer) or a 5'-triphosphate (RNA primer) group. Rapid kinetic measurements revealed that upon encountering the blocking primer, the holoenzyme either dissociates from DNA (approximately 40%) or strand-displaces the blocking strand (approximately 60%). The two blocking oligonucleotides (DNA or RNA) induce a 30-50-fold increase in the rate of holoenzyme dissociation, with both polymerase and clamp proteins dissociating simultaneously. Inhibition of ATP hydrolysis by ATP-gamma-S did not have a measurable effect upon holoenzyme dissociation from DNA. The presence of gp32, the single-strand binding protein, caused a small (3-fold) increase in the rate constant for dissociation.  相似文献