Controlled elimination of intracellular H(2)O(2): regulation of peroxiredoxin, catalase, and glutathione peroxidase via post-translational modification

The predominant enzymes responsible for elimination of hydrogen peroxide (H(2)O(2)) in cells are peroxiredoxins (Prxs), catalase, and glutathione peroxidases (GPxs). Evidence suggests that catalytic activities of certain isoforms of these H(2)O(2)-eliminating enzymes are extensively regulated via posttranslational modification. Prx I and Prx II become inactivated when phosphorylated on Thr(90) by cyclin B-dependent kinase Cdc2. In addition, the active-site cysteine of Prx I-IV undergoes a reversible sulfinylation (oxidation to cysteine sulfinic acid) in cells. Desulfinylation (reduction to cysteine) is achieved by a novel enzyme named sulfiredoxin. c-Abl and Arg nonreceptor protein tyrosine kinases associate with catalase in cells treated with H(2)O(2) by mechanisms involving the SH3 domains of the kinases and the Pro(293)PheAsnPro motif of catalase and activate catalase by phosphorylating it on Tyr(231) and Tyr(386). Similarily, GPx1 is activated by c-Abl- and Arg-mediated phosphorylation. The tyrosine phosphorylation is critical for ubiquitination-dependent degradation of catalase.     

Analysis of photon beam exit dose using photon point kernels

The Monte Carlo method is used to analyse the dose fall-off at the exit surface of a megavoltage photon beam. The convolution/superposition method of dose calculation using Monte-Carlo-generated homogeneous photon kernels is shown to be in error for exit dose calculation. Instead, photon kernels that incorporate modelling of the exit surface were generated, also using Monte Carlo, to analyse the problem, and the calculated dose fall-off using these kernels agrees well with measured data. In addition, the physics underlying the characteristics of the dose fall-off is analysed based on complete Monte Carlo modelling. Practical improvements to the convolution/superposition method are suggested.     

Thermal behavior,morphology and the determination of the polymer-polymer interaction parameter of polycarbonate-poly(butylene terephthalate) blends

Blends of bisphenol-A polycarbonate (PC, poly(oxycarbonyloxy-1,4-phenylene-2-isopropylidene-1,4-phenylene)) and poly(butylene terephthalate) (PBT, poly(oxytetramethyleneoxy-terephthaloyl)) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were prepared by screw extrusion and solution casting with mass fractions of PC in the blends varying from 0,90 to 0,10. From the measured glass transition temperature (T_g) and apparent mass fractions of PC and PBT dissolved in each phase, it appears that the PBT dissolves more in the PC-rich phase than does the PC in the PBT-rich phase. Also, compatibility is greater in the case of extruded blends than in the case of solutioncast blends. The values of the Flory-Huggins polymer-polymer interaction parameter (χ₁₂) were determined and found to range from 0,042 to 0,033 for extruded blends at 250°C and from 0,054 to 0,039 for solution casting at 25°C. The χ₁₂ decreases with increase of PBT content throughout the investigated composition range. From the T_g's, the microscopy study and the extrudate swell ratios, it is concluded that compatibility is achieved in the blends having mass fractions 0,90, 0,20 and 0,10 of PC, but that these blends are not microscopically homogeneous.     

Effect of biphenyl dimethyl dicarboxylate on the humoral immunosuppression by ethanol

The present study was undertaken to investigate the effect of biphenyl dimethyl dicarboxylate (PMC) on the humoral immunosuppression by ethanol (EtOH) in ICR mice. PMC at a dose of 6 mg/kg was orally administered to mice daily for 28 consecutive days, and the control mice were given vehicle. Mice treated with EtOH were given freely with 20% EtOH instead of water. The results of this study are summarized as follows; a gain of body weight and the relative weights of spleen and liver were significantly increased by combination of PMC and EtOH, as compared with those in mice treated with EtOH alone. Splenic plaque forming cells (PFC) and hemagglutination (HA) titers to sheep red blood cells (SRBC), and the secondary IgG antibody response to bovine serum albumin (BSA) were decreased by the treatment of EtOH alone, then restored to normal level by PMC treatment. The elevations of serum glutamic-pyruvic transaminase (S-GPT) and total protein levels caused by EtOH were reduced to normal level by the combination of PMC and EtOH. In addition, lower serum albumin and A/G ratio were also increased to normal level. These findings indicate that PMC has a protective effect against EtOH-induced humoral immunosuppression.     

Improvement of Accuracy in a High-Capacity, Six Degree-of-freedom Load Cell: Application to Robotic Testing of Musculoskeletal Joints

This study investigated a previously unaccounted for source of error in a high-capacity, six degree-of-freedom load cell used in multi-degree-of-freedom robotic testing of musculoskeletal joints, an application requiring a load cell with high accuracy in addition to high load capacity. A method of calibration is presented for reducing the error caused by changes in universal force-moment sensor (UFS) orientation within a gravitational field. Uncorrected, this error can exceed a magnitude of 1% of the full-scale load capacity—the manufacturer-stated accuracy of the UFS. Implementation of the calibration protocol reduced this error by approximately 75% for a variety of loading conditions. This improvement in load cell accuracy (while maintaining full load capacity) should improve both the measurement and control of specimen kinetics by robotic/UFS and other biomechanical testing systems. © 1999 Biomedical Engineering Society. PAC99: 8719Rr, 8780Vt, 0620Fn, 0620Dk, 8719Ff     

Hypertrophic obstructive cardiomyopathy with infundibular stenosis treated by alcohol ablation therapy

This report describes an uncommon case of hypertrophic obstructive cardiomyopathy (HOCM) accompanying infundibular stenosis of the right ventricle treated by alcohol ablation therapy, in a 28-yr-old male patient presenting with dyspnea on exertion. HOCM with infundibular stenosis was detected by echocardiogram and cardiac catheterization and patient has dynamic obstructions of both ventricular outflow tracts. We performed alcohol ablation therapy to improve clinical symptoms and to relieve dynamic obstructions of both ventricular outflow tracts. This is the first case in which HOCM with infundibular stenosis of the right ventricle was treated by alcohol ablation therapy.     

Gemella bacteraemia characterised by 16S ribosomal RNA gene sequencing

AIMS: To define epidemiology, clinical disease, and outcome of gemella bacteraemia by 16S rRNA gene sequencing. To examine the usefulness of the Vitek, API, and ATB systems in identifying two gemella species. METHODS: All alpha haemolytic streptococci other than Streptococcus pneumoniae isolated from blood cultures during a six year period were identified by conventional biochemical methods, the Vitek system, and the API system. 16S rRNA gene sequencing was performed on all isolates identified by both kits as gemella with >or= 95% confidence or by either kit as any bacterial species with < 95% confidence. The ATB expression system was used to identify the two isolates that were defined as gemella species by 16S rRNA gene sequencing. RESULTS: Of the 302 alpha haemolytic streptococci other than S pneumoniae isolated, one was identified as Gemella morbillorum, and another as Gemella haemolysans by 16S rRNA gene sequencing. The patient with monomicrobial G morbillorum bacteraemia was a 66 year old man with community acquired infective endocarditis with septic thromboemboli. The patient with G haemolysans bacteraemia was a 41 year old woman with hospital acquired polymicrobial bacteraemia during the neutropenic period of an autologous bone marrow transplant for non-Hodgkin's lymphoma, the first case of its kind in the English literature. The API and ATB expression systems only identified the second strain as G haemolysans at 94% and 99% confidence, respectively, whereas the Vitek system identified none of the two strains correctly at > 70% confidence. CONCLUSIONS: Gemella bacteraemia is uncommon. 16S rRNA gene sequencing is the method of choice for identification of gemella and gemella-like isolates.     

HLA and Thyrotoxicosis (Graves' Disease) in Chinese

HLA locus A and B typing was performed on 86 Chinese thyrotoxicosis (Graves' Disease) patients and 238 normal Chinese subjects. The frequency of HLA-Bw46 (Sin 2) was found to be significantly higher among the patients than controls (X²= 26.15, corrected P <.003, relative risk = 3.74). The risk associated with Bw46 was reflected in the Bw46 heterozygotes. The relative risks of the joint occurrence of Bw46/B40 and Bw46/B13 were 8.74 and 5.88 respectively.     

Cardiac responses to pressor challenges in congenital central hypoventilation syndrome

Summary Question of the Study   Congenital central hypoventilation syndrome (CCHS) subjects exhibit diminished respiratory-related heart rate variation in addition to defining characteristics of CO₂ insensitivity and reduced ventilatory drive during sleep. Loss of cardiovascular and breathing coupling may diminish blood pressure influences on breathing; such influences may be determined by evaluating cardiorespiratory responses to different pressor challenges.
Patients and Methods   Ten children with CCHS and 10 age- and gender-matched controls were subjected to a forehead cold pressor challenge and to Valsalva maneuvers. Heart and respiratory rates and variability during 30-s baseline and 120-s challenge periods were assessed with scatterplot displays and by analysis of variance procedures.
Results   Cold pressor challenges enhanced breathing efforts and increased respiratory-related heart rate variation in controls but not in CCHS patients, while lower frequency heart rate variability increased in both controls and CCHS subjects. Heart rate variation resulting from voluntary expiratory efforts was present but slightly reduced in CCHS. Respiratory and cardiac rate trends differed in control and CCHS cases.
Conclusions   More-rapidly changing heart rate variation from spontaneous or reflexively-induced sources is diminished in CCHS but remains intact from voluntary expiratory ­efforts, as does slower variation. Loss of reflexive influences on breathing from blood pressure changes may attenuate a source of respiratory drive.