Age-related decreases in lymphocyte protein kinase C activity and translocation are reduced by aerobic fitness

This study investigated the effects of advancing age and long-term aerobic fitness on lymphocyte protein kinase C (PKC) activity and translocation. Lymphocytes were obtained from young (20-36 years old) and older (61-78 years old) healthy men who were either aerobically conditioned or deconditioned. Both baseline PKC activity and the response of this enzyme to the direct PKC stimulating agent, phorbol 12-myristate, 13-acetate (PMA) or to the mitogen, phytohaemagglutinin (PHA), were measured in partially purified extracts of cytosolic and membranous fractions of lymphocytes. Basal PKC activity, PMA-induced redistribution of PKC, and PHA-induced enhancement of PKC activity were reduced among older subjects in both lymphocyte cytosolic and membranous fractions. However, the magnitudes of these reductions were smaller among the older subjects who were aerobically fit. Lymphocyte PKC activity and translocation may be biological markers of aging, and the maintenance of aerobic fitness into later life may serve to slow the rate at which activation of this enzyme declines during senescence.     

Rare detection of hepatitis B and hepatitis C virus genomes by polymerase chain reaction in seronegative donors with elevated alanine aminotransferase

BACKGROUND: Since screening for antibody to hepatitis C virus (HCV) was introduced in 1990, posttransfusion hepatitis has been reduced to nearly background levels. This has led to reconsideration of the value of testing donated blood for elevated alanine aminotransferase (ALT). The contribution of ALT testing in detecting seronegative infection was evaluated by the performance of polymerase chain reaction (PCR) for hepatitis B virus (HBV) or HCV in plasma from ALT-elevated blood units. STUDY DESIGN AND METHODS: Testing was performed on 375 units of plasma, derived from an equivalent of 47,500 blood donations, with a highly sensitive hemi-nested PCR procedure. Using a triplet of primers directed at the conserved regions of HBV DNA and 5'-noncoding regions of HCV RNA, the hemi-nested PCR assay can reliably amplify 10 viral molecules to levels detectable in ethidium bromide-stained agarose gels. Pools of plasma from groups of four donors were screened with hemi-nested PCR. For any reactive pools, the plasma from individual donors was retested twice on different aliquots. RESULTS: Two of 375 units, both with midrange ALT elevation, were repeatedly reactive in hemi-nested PCR (one each for HBV DNA and HCV RNA). However, samples from the two suspect donors tested 9 and 5 months later revealed no seroconversion, elevated ALT, or viral genomes in hemi-nested PCR. CONCLUSION: The lack of confirmed HBV or HCV infection in this study representing an estimated 47,500 voluntary blood donations suggests that routine ALT testing for further prevention of posttransfusion hepatitis after exclusion of HBV- and/or HCV-seropositive blood may be superfluous.     

60Coγ射线局部辐射后小鼠非辐射区域骨髓巨核细胞的变化

目的:临床局部辐射条件下会造成非辐射区域组织及细胞功能损害,最为突出的是对造血功能的影响。实验建立60Coγ射线左半身辐射动物模型,观察局部电离辐射对其非辐射区域骨髓巨核细胞的影响。方法:实验于2003-10/2005-03在解放军第三军医大学辐照中心和全军复合伤研究所完成。①实验动物:6～8周龄SPF级雄性昆明小鼠180只,随机数字表法分为正常对照组、全身辐射组、左半身辐射组、全身屏蔽辐射组,45只/组。②实验方法:全身辐射组小鼠固定于辐射架内;左半身辐射组小鼠麻醉后固定体位,用铅砖屏蔽右半身;全身屏蔽辐射组小鼠麻醉固定体位,用铅砖屏蔽全身。以60Coγ射线一次性辐射,剂量率68.46cGy/min。正常对照组不作任何干预。③实验评估:辐射后不同时相检测小鼠血清丙二醛含量及超氧化物歧化酶活性变化,计数外周血血小板,检测骨髓巨核祖细胞集落形成单位,观察骨髓组织病理改变及CD41a、CD61的表达。结果:全身辐射组第8天死亡2只,第9天死亡4只,其余各组无脱失。①外周血血小板计数:辐射后第2,7天,左半身辐射组外周血血小板数量显著低于正常对照组(P<0.01),但高于全身辐射组(P<0.01)。②血清丙二醛含量及超氧化物歧化酶活性变化:辐射后第2,9天,左半身辐射组血清丙二醛含量显著高于正常对照组(P<0.01),低于全身辐射组(P<0.01);血清超氧化物歧化酶活性显著低于正常对照组(P<0.01),高于全身辐射组(P<0.01)。③骨髓巨核祖细胞集落形成单位的变化:与正常对照组比较,辐射后6h左半身辐射组非辐射侧的巨核祖细胞集落形成单位显著降低(P<0.01),高于全身辐射组及左半身辐射组(P<0.01)。④骨髓组织病理改变:正常对照组有核细胞比例较高,分布均匀,并见多量散在分布的细胞龛;辐射2d后,左半身辐射组非辐射侧骨髓有核细胞较正常对照组减少,但好于全身辐射组、左半身辐射组。⑤骨髓CD41a及CD61表达的变化:辐射后2d与正常对照组比较,左半身辐射组非辐射侧骨髓CD41a及CD61阳性细胞数和相对荧光强度均显著降低(P<0.01),但高于全身辐射组、左半身辐射组(P<0.01)。结论:局部电离辐射作用后,可导致小鼠非辐射区域骨髓巨核细胞增殖能力降低,血小板减少,产生功能障碍。氧自由基激活可能参与了该损伤过程。     

Update on infective endocarditis

With infective endocarditis afflicting 15,000 patients each year and with a mortality rate that still hovers at almost 40%, the disease remains a very serious health problem. Surprisingly, the incidence has not declined over the last 30 years, and now with more health care interventions, such as pacer/defibrillators, and an increasingly elderly population with degenerative valvular heart disease, the number susceptible to endocarditis is actually increasing. Given the weak evidence for endocarditis prophylaxis, there remains a large population at risk. Much has been learned recently about the pathogenesis of endocarditis, including the role of endothelial damage, platelet adhesion, and microbial adherence to the vegetation or intact valvular tissue. Three-fourths of patients have preexisting structural heart disease. Once infection is manifest, major cardiac complications include congestive heart failure, embolization, mycotic aneurysms, renal dysfunction, and abscess formation. The diagnosis of endocarditis has been enhanced recently by modifications in the Duke criteria to include the use of transesophageal echocardiography and microbial antibody titers. Surgery continues to play an important role, with criteria for emergency, urgent, and early surgery now defined. The major organisms involved in infective endocarditis include streptococci and staphylococcus (representing 75% or so of all cases). Enterococcal infections account for many of the remaining cases, although small series and case reports suggest almost all organisms that infect humans can be implicated at times. A sizeable number of "culture-negative" cases still occur despite all the improvements in diagnostic methodology. Recent guidelines for the diagnosis, treatment, and management of infective endocarditis from the American Heart Association are reviewed and the issues surrounding prophylaxis are summarized. International cooperative databases are now being developed that hold promise for a continual reexamination of the epidemiology of this highly aggressive disease and may help provide sorely needed prospective trial data that will enhance our understanding and treatment.     

Cardiovascular and renal toxicity of a nonionic radiographic contrast agent after cardiac catheterization. A prospective trial

STUDY OBJECTIVE: To determine the incidence of cardiovascular and renal toxicity of a nonionic contrast agent when used for cardiac catheterization, and to assess the value of electrolytes and urinalysis results as predictors of nephropathy induced by a contrast agent. STUDY DESIGN: Nonrandomized trial using a criterion standard and a cohort analytic study with a 48-hour follow-up. SETTING: Referral-based university hospital. PATIENTS: Convenience sample of patients having diagnostic cardiac catheterization. Renal function and clinical status were evaluated at baseline in 1,144 patients; at 24 hours in 1,077 (94%); and at 48 hours in 663 (57%). INTERVENTIONS: After patients received saline for hydration, coronary angiography and left ventriculography were done with iopamidol (average dose, 203 +/- 56 cc). MEASUREMENTS AND MAIN RESULTS: The definite and possible incidence of major acute cardiovascular complications from nonionic contrast media was 0.2% and 0.7%, respectively. The mean serum creatinine level increased 11.5 mumol/L from baseline at 24 hours (P less than 0.0001) and 16.8 mumol/L from baseline at 48 hours (P less than 0.0001). Results in a randomly selected training sample were studied to determine predictors of a rise in serum creatinine of 44.2 mumol/L or more. The baseline serum creatinine level and age were significant predictors of renal injury, but hypertension, diabetes mellitus, congestive heart failure, vascular disease, the volume of contrast agent injected or baseline values of urinary variables did not predict nephrotoxicity. In an independent validation sample, only the baseline serum creatinine level was confirmed as a predictor of nephrotoxicity, whereas age was not. A model that predicted contrast-induced nephropathy by the serum creatinine level showed an exponential increase in the risk for nephrotoxicity if the baseline level was 106.1 mumol/L or higher. CONCLUSIONS: Patients have a small but significant rise in serum creatinine after cardiac catheterization with a nonionic contrast agent. Baseline renal insufficiency is the only confirmed predictor of nonionic contrast-induced nephrotoxicity.     

Safety and efficacy of inferior vena caval occlusion to rapidly alter ventricular loading conditions in idiopathic dilated cardiomyopathy

To investigate the safety and efficacy of inferior vena caval (IVC) balloon occlusion for preload alteration in humans, 13 patients with dilated cardiomyopathy were studied before and during repeated (total of 78) IVC occlusions. Left and right ventricular (LV and RV) micromanometer pressures were simultaneously measured and M-mode and 2-D echocardiograms were recorded at end expiration. Complications were limited to abdominal discomfort in 2 patients. With IVC occlusion, RV collapse fluoroscopically shifted the heart toward midline and ventricular septal motion was frequently disordered. Significant (p = 0.001) changes occurred in RV and LV systolic peak pressures (from 19 +/- 6 to 12 +/- 5 mm Hg and from 129 +/- 34 to 109 +/- 25 mm Hg, respectively). LV and RV end-diastolic pressures also decreased significantly (from 18 +/- 7 to 6 +/- 6 mm Hg and from 5 +/- 3 to 2 +/- 2 mm Hg, respectively) (both p less than or equal to 0.0055). Similarly, LV end-diastolic diameter decreased 13% (from 61 +/- 11 to 53 +/- 12 mm, p = 0.0002). Mean heart rate did not change significantly (from 76 +/- 19 to 78 +/- 21 beats/min). Thus, IVC balloon occlusion provides a safe method of repeatedly altering loading conditions in humans. This approach allows for acquisition of important information regarding cardiac chamber dynamics while minimizing the effects of reflex mechanisms and avoiding use of pharmacologic agents.     

Position as a variable for cardiovascular responses during exercise

Twenty-one normal young male subjects underwent resting and exercise (bicycle) radionuclide angiography in the full supine and 70 degrees upright tilt positions in order to examine the effects of position on left ventricular size and performance, hemodynamics, and exercise duration. All subjects also underwent full (90 degrees) upright bicycle ergometry with respiratory gas analysis to establish the level of maximal exercise capacity for each. Body position significantly (p less than 0.05) affected resting and exercise cardiovascular parameters. End-diastolic and endsystolic left ventricular volumes and stroke volume were larger in the supine position, both at rest and during exercise. The cardiac output at rest and during exercise were comparable for the two positions; an increase in resting and exercise heart rate in the 70 degrees tilt position compensated for the reduced stroke volume of this posture. At maximal exercise, the 70 degrees upright position was associated with a greater response in left ventricular ejection fraction, otherwise this parameter was not position related. Exercise capacity, in terms of duration and workload, was significantly higher in the supine (1870 +/- 390 s) and full upright (1830 +/- 250 s) positions than in the 70 degrees tilt position (1730 +/- 260 s). Changes in body position significantly alter parameters of ventricular, cardiovascular, and exercise performance.     

Role of plasminogen activator inhibitor-1 in promoting fibrin deposition in rabbits infused with ancrod or thrombin

The role of defective fibrinolysis caused by elevated activity of plasminogen activator inhibitor-1 (PAI-1) in promoting fibrin deposition in vivo has not been well established. The present study compared the efficacy of thrombin or ancrod, a venom-derived enzyme that clots fibrinogen, to induce fibrin formation in rabbits with elevated PAI-1 levels. One set of male New Zealand rabbits received intravenous endotoxin to increase endogenous PAI-1 activity followed by a 1-hour infusion of ancrod or thrombin; another set of normal rabbits received intravenous human recombinant PAI-1 (rPAI-1) during an infusion of ancrod or thrombin. Thirty minutes after the end of the infusion, renal fibrin deposition was assessed by histopathology. Animals receiving endotoxin, rPAI-1, ancrod, or thrombin alone did not develop renal thrombi. All endotoxin-treated rabbits developed fibrin deposition when infused with ancrod (n = 4) or thrombin (n = 6). Fibrin deposition occurred in 7 of 7 rabbits receiving both rPAI-1 and ancrod and in only 1 of 6 receiving rPAI-1 and thrombin (P < .01). In vitro, thrombin but not ancrod was inactivated by normal rabbit plasma and by purified antithrombin III or thrombomodulin. The data indicate that elevated levels of PAI-1 promote fibrin deposition in rabbits infused with ancrod but not with thrombin. In endotoxin-treated rabbits, fibrin deposition that occurs with thrombin infusion may be caused by decreased inhibition of procoagulant activity and not increased PAI-1 activity.     

The regulation of hemopoiesis in long-term bone marrow cultures. II. Stimulation and inhibition of stem cell proliferation

The isolation of a DNA synthesis inhibitor (NBME fraction IV) and stimulator (RBME fraction III) specific for the hemopoietic stem cell (CFU-s) from freshly isolated normal adult and regenerating murine bone marrow, respectively, has been well documented. We have utilized long- term liquid bone marrow cultures in a further analysis of the role of these factors in the regulation of CFU-s proliferation. Our results show that shortly after feeding, at a time when the cultured CFU-s are actively proliferating, high levels of the hemopoietic stem cell proliferation stimulator fraction III can be isolated from the culture medium. In contrast, the presence of essentially noncycling CFU-s found in cultures fed 8-10 days previously correlates with high levels of the hemopoietic stem cell inhibitor fraction IV. These results suggest that a certain balance between these factors determines CFU-s proliferation in the long-term cultures. In support of this, DNA synthesis in actively cycling CFU-s in the long-term cultures is inhibited for at least 3 days by the addition of excess NBME fraction IV (inhibitor). Furthermore, DNA synthesis in noncycling cultured CFU-s is stimulated for at least 5 days by the addition of RBME fraction III (stimulator).