低氧暴露对运动性贫血大鼠抗氧化能力的影响

目的:观察低氧暴露对运动性贫血大鼠某些抗氧化酶的影响,探讨低氧条件下抗氧化系统的反应是否有利于改善运动性贫血。方法:实验于2005-07/09在广东省高等学校运动生物化学教学重点实验室完成。选择6周龄健康雄性SD大鼠40只,均为运动性贫血动物模型,大鼠适应环境1周后采用6周递增负荷跑台运动方式建立。按随机数字表法分为1h低氧暴露组、2h低氧暴露组和间歇性低氧暴露组、常氧恢复组,每组10只。采用人工常压低氧环境,低氧浓度控制在14.5%左右,按分组每天在常压低氧舱进行1,2h和间歇性低氧暴露(低氧暴露1h,中间间歇3h,再低氧暴露1h),其余时间在舱外常氧中自由活动,每周6d,持续3周。常氧恢复组大鼠在常氧中自由活动。3周后测试运动性贫血大鼠血清丙二醛含量、超氧化物歧化酶活性和血浆过氧化氢酶、谷胱甘肽过氧化酶活性。结果:纳入动物40只,均进入结果分析。①低氧暴露3周后1h低氧暴露组、2h低氧暴露组、间歇性低氧暴露组血清丙二醛含量均显著低于常氧恢复组[分别为(2.62±0.16),(2.60±0.22),(2.55±0.06),(3.36±0.34)μmol/L,P<0.05]。②低氧暴露3周后血清超氧化物歧化酶和血浆谷胱甘肽过氧化酶、过氧化氢酶活性均高于常氧恢复组,2h低氧暴露组与常氧恢复组比较差异有显著性意义[分别为(4239.68±169.53),(3190.30±339.40)μkat/L;(20622.46±2002.07),(15556.44±607.79)μkat/L;(50.01±6.67),(35.17±4.50)μkat/L,P<0.05]。③各低氧暴露组间除2h低氧暴露组血清超氧化物歧化酶活性显著高于1h低氧暴露组外[分别为(4239.68±169.53),(2126.41±161.20)μkat/L,P<0.05],其他指标组间差异无显著性意义(P>0.05)。结论:低氧暴露可提高运动性贫血大鼠机体的抗氧化能力,有利于促进运动性贫血的恢复。     

Commentary on the safety of red cells preserved in extended-storage media for neonatal transfusions

Red cells preserved in extended-storage media are the standard product dispensed by many regional blood centers. When the red cells are intended for neonatal transfusion, concern exists about the safety of the relatively high quantities of additives present in these media. Definitive studies to address these concerns are not available. Therefore, to estimate the effects of additives and to delineate circumstances in which they might be harmful, the quantities transfused in defined clinical settings were calculated, and the following recommendations are offered for transfusing infants less than 4 months of age. First, red cells preserved in extended-storage media should present no substantive risks when used for small-volume (approximately 10 mL/kg) transfusions of premature infants and can be used without additional processing. Second, the risks of the most premature neonatal patients or those with severe renal and/or hepatic insufficiency cannot be defined clearly, and, because data are not available to ensure safety for these infants, removal of the additive medium and resuspension of the red cells in saline or albumin solution immediately before transfusion are recommended. Third, following a similar rationale, it seems prudent to avoid using entire units of red cells preserved in extended-storage media in massive transfusion settings (e.g., exchange transfusion, cardiac surgery, and extracorporeal membrane oxygenation). In these settings, the preservative medium should be removed and the red cells resuspended in the fluid that is most appropriate for the procedure that is planned. It must be emphasized that these recommendations are based on calculations and hypothetical settings, not actual data. Accordingly, they are tentative and should be altered as definitive information becomes available.     

Intraindividual Reproducibility of Heart Rate Variability

Heart rate variability was determined from three consecutive Holter recordings performed on days 1, 7, and 28 in 17 normal subjects, in 13 patients with angiographically normal coronary arteries, and in 9 patients with remote myocardial infarctions. Group data of several time and frequency domain measures of heart rate variability were highly reproducible (correlation coefficients 0.629–0.894). However, some individuals exhibited considerably larger day-to-day variations in heart rate variability. Single heart rate indices differed by up to 50% between two Holter recordings. Such potential differences must be considered when repeated heart rate variability determinations are used to assess changes in neurocardiac reflex regulation or effects of therapeutic interventions.     

Mycobacterial Infections After Renal Transplantation

Mycobacterial infections occurred in 11 of 633 (1.7 per cent)recipients of successful renal transplants. There were no casesof tuberculosis in patients receiving chemoprophylaxis, butamongst those who did not receive prophylaxis disease occurredin six of the 27 (22 per cent) high-risk patients. The majorcause of morbidity during treatment was renal allograft rejection,largely due to reduction in immunosuppressive drug therapy.     

Mid-trimester loss--appraisal of a screening protocol

The main causes for mid-trimester loss are known. There is likely to be overlap with those of first trimester loss, but the proportions may be different. We wished to perform an aetiological survey in a large population of patients with a history of recurrent miscarriage, for possible explanations for their second trimester miscarriages. Database analysis of 636 patients attending a UK University Teaching Hospital dedicated miscarriage clinic between 1991 and 1996 revealed a 25% prevalence (n = 158) for second trimester miscarriage. Results from an investigative screening protocol were positive in 50% of cases: 33% (n = 52) tested positive for antiphospholipid syndrome (APS); 8% (n = 13) fulfilled strict criteria for cervical incompetence; there was a 4% prevalence of uterine anomaly; 3% for infection (n = 5) and 2% of patients (n = 3) proved to be hypothyroid. Importantly, dual pathology was found in 5% of patients with a history of second trimester miscarriage. As idiopathic mid-trimester loss is a diagnosis by exclusion, a high index of suspicion is required, as are modern diagnostic techniques.      

Breast MR imaging with loop-gap resonators

Breast images obtained at 1.5 T using a loop-gap resonator pair as both the excitation and detection device are presented. The efficiency of this approach is high, as judged by the low level of radio frequency (RF) power required to obtain a 90 degree pulse and the uniformity of the RF field within the resonator pair. A modification of the pair geometry provides for reasonable observation of the tissues through the chest wall and laterally to the axillae.     

A Fractally Coated, 1.3 mm2 High Impedance Pacing Electrode

Minimizing the geometric surface area of pacing electrodes increases impedance and reduces the current drain during stimulation, provided that voltage (pulse-width) thresholds remain unchanged. This may be feasible by coating the electrode surface to increase the capacity of the electrode tissue interface and to diminish polarization. Ten unipolar, tined leads with a surface area of 1.3 mm² and a “fractal” coating of Iridium (Biotronik SD-V137) were implanted in the ventricle, and electrogram amplitude (unfiltered), slew-rate, pacing threshold (0.5 ms), and impedance (2.5 V; 0.5 ms) were measured by the 5311 PSA (Medtronic). On days 0, 2, 5, 10, 28, 90, 180, 360 postimplant, sensing threshold (up to 7.0 mV, measuring range 1–14 mV on day 360 only) and the strength duration curve (0.5–4.0 V; 0.03–1.5 ms; steps: 0.5 V; 0.01 ms, respectively) were determined, the minimum charge delivered per pulse (charge threshold), and the impedance were taken from pacemaker telemetry (Intermedics 294–03). Data were compared with those of an earlier series of 20 unipolar, tined TIR-leads (Biotronik) with a surface area of 10 mm² and a “fractal” coating of titanium nitride. With the model SD-V137 versus TIR, intraoperative electrogram amplitudes were 15.1 ± 6.1 versus 14.4 ± 3.9 mV(NS), slew rates 3.45 ± 1.57 versus 1.94 ± 1.06 V/s (P < 0. 05), pacing thresholds 0.16 ± 0.05 versus 0.52 ± 0.15 V (P < 0.01) and impedance measurements 1,136 ±175 versus 441 ± 73 Ω (P < 0.0001), respectively. During follow-up, sensing thresholds were the same with both leads. Differences in pulse width thresholds lost its significance on day 28 but resumed on day 360 (SD-V137: 0.08 ± 0.04 ms; TIR: 0.16 ± 0.06 ms at 2.5 V; P < 0.01). With an electrode surface of 1.3 mm², charge per pulse and impedance consistently differed from control, beingO.15 ± 0.15 versus 0. 66 ± 0. 20 μC (P < 0.001) and 1,344 ± 376 versus 538 ± 79 Ω, respectively, one year after implantation (P < 0.0001). In summary, “fractally” coated small surface electrodes do not compromise sensing; by more than doubling impedance against controls they offer pacing thresholds (mainly in terms of charge) that are significantly lower than with the reference electrode.