Meta-analysis of intravenous dipyridamole-thallium-201 imaging (1985 to 1994) and dobutamine echocardiography (1991 to 1994) for risk stratification before vascular surgery

OBJECTIVES: This study evaluated the prognostic value of abnormal test results with pharmacologic stress with regard to perioperative and long-term outcomes in a large population of candidates for vascular surgery. BACKGROUND: Although numerous studies have demonstrated the prognostic value of dipyridamole-thallium-201 myocardial perfusion and dobutamine echocardiography in vascular surgery candidates, a synopsis of predictive estimates is difficult because of individual study variability in pretest clinical risk, sample size and study design. METHODS: A systematic review of published reports on preoperative pharmacologic stress risk stratification from the MEDLINE data base (1985 to 1994) identified 10 reports on dipyridamole-thallium-201 myocardial perfusion (1,994 patients) and 5 on dobutamine stress echocardiography (446 patients). Random effects models were used to calculate summary odds ratios and 95% confidence intervals. RESULTS: Summary odds ratios for death or myocardial infarction and secondary cardiac end points were greater for dobutamine echocardiographic dyssynergy (14- to 27-fold) than for dipyridamole-thallium-201 redistribution (4-fold); wider confidence intervals were noted with dobutamine echocardiography. Pretest coronary disease probability was correlated with the positive predictive value of a reversible thallium-201 defect (r=0.70), increasing sixfold from low to high risk patient subsets. Cardiac event rates were low in patients without a history of coronary artery disease (1% in 176 patients) compared with patients with coronary disease and a normal or fixed-defect pattern (4.8% in 83 patients) and one or more thallium-201 redistribution abnormality (18.6% in 97 patients, p=0.0001). CONCLUSIONS: Meta-analysis of 15 studies demonstrated that the prognostic value of noninvasive stress imaging abnormalities for perioperative ischemic events is comparable between available techniques but that the accuracy varies with coronary artery disease prevalence.     

Hypertension in autosomal dominant polycystic kidney disease

Hypertension occurs frequently in autosomal dominant polycystic kidney disease. Increased activity of the renin-angiotensin system contributes to the development and maintenance of hypertension before the development of renal failure. Angiotensin-converting enzyme inhibitors are indicated for treatment of hypertension before the development of renal failure, but in severe renal failure these agents may cause further deterioration in renal function. Treatment of hypertension may not retard the progression of renal failure but is necessary for the prevention of cardiovascular disease.     

Diagnostic imaging strategies in small animal nephrology

The diagnostic imaging methods most readily available to the private practitioner are survey radiography, radiographic contrast procedures, and ultrasonography. Nuclear medicine imaging techniques are available at referral centers. The advantages and disadvantages of these methods as well as the favored strategies of the authors in their utilization for the diagnosis of renal disorders in the cat and dog are discussed.     

TGF-beta and the endothelium during immune injury

During immune injury, activation of endothelial cells by inflammatory cytokines stimulates leukocyte adhesion to the endothelium, turns the endothelium from an anticoagulant surface to one that is frankly procoagulant, and results in the release of vasoactive mediators and growth factors. Cytokine activation of endothelial cells also results in increased endothelial cell TGF-beta 1 synthesis and enhanced activation of latent TGF-beta, the latter involving a shift of plasmin production from the apical to subendothelial surface. In cytokine-stimulated endothelial cells, TGF-beta hinders leukocyte adhesion and transmigration via inhibition of IL-8 and E-selectin expression. TGF-beta also profoundly diminishes cytokine-stimulated inducible nitric oxide synthase production and instead augments endothelial nitric oxide synthase expression. Thus, some of the TGF-beta actions on endothelium during immune activation can viewed as immunosuppressive. TGF-beta also influences mechanisms of vascular remodeling during the healing phase of immune injury. It stimulates PDGF-B synthesis by endothelial cells, causes bFGF release from subendothelial matrix, and promotes VEGF synthesis by non-endothelial cells. Together these mediators control angiogenesis, a critical component of the vascular repair phenomenon. Further, endothelial cell derived PDGF-B and bFGF influence the proliferation and migration of neighboring cells. Thus, endothelial cells and TGF-beta actions on the endothelium play important roles both during the initial phase of immune injury and during the later remodeling phase.     

The effect of keyboard keyswitch make force on applied force and finger flexor muscle activity

The design of the force-displacement characteristics or 'feel' of keyboard keyswitches has been guided by preference and performance data; there has been very little information on how switch 'feel' alters muscle activity or applied force. This is a laboratory-based repeated measures design experiment to evaluate the effect of computer keyboard keyswitch design on applied finger force and muscle activity during a typing task. Ten experienced typists typed on three keyboards which differed in keyswitch make force (0.34, 0.47 and 1.02 N) while applied fingertip force and finger flexor electromyograms were recorded. The keyboard testing order was randomized and subjects typed on each keyboard for three trials, while data was collected for a minimum of 80 keystrokes per trial. No differences in applied fingertip force or finger flexor EMG were observed during typing on keyboards with switch make force of 0.34 or 0.47 N. However, applied fingertip force increased by approximately 40% (p < 0.05) and EMG activity increased by approximately 20% (p < 0.05) when the keyswitch make force was increased from 0.47 to 1.02 N. These results suggest that, in order to minimize the biomechanical loads to forearm tendons and muscles of keyboard users, keyswitches with a make force of 0.47 N or less should be considered over switches with a make force of 1.02 N.     

Endogenous glutamate levels regulate nerve growth factor mRNA expression in the rat dentate gyrus

The levels of nerve growth factor (NGF) mRNA can be regulated in vitro and in vivo in the hippocampal formation by events associated with pharmacological activation of glutamate receptors. In the present study, the level of NGF mRNA in the hippocampal formation was examined following an intrahippocampal injection of 1 nmole fluorocitrate, which temporarily inhibits the astrocyte metabolic activity in vivo. Consistent with previous findings, fluorocitrate treatment significantly increased glutamate levels and decreased glutamine levels in the dentate gyrus as determined by in vivo microdialysis. The increased ratio of glutamate to glutamine was followed by a significant increase in NGF mRNA expression selectively in dentate gyrus granule cells. The effects of increasing glutamate levels were blocked by pretreatment with 50 nmole 2-amino-5-phosphonovalerate (AP5), a competitive antagonist that acts at the N-methyl-D-aspartate (NMDA) glutamate receptor subtype. These findings suggest that NGF mRNA expression is regulated, in part, by changes in endogenous glutamate levels, partially through enhanced excitatory neurotransmission through NMDA receptors.     

Biological effects of continuous exposure of embryos and young chickens to electromagnetic fields emitted by video display units

The effects of continuous exposure of embryos and young chickens to electromagnetic fields (EMFs) emitted by video display units (VDUs) were investigated. Embryos and brood were continuously exposed during embryonic and postembryonic phases to EMFs emitted by two types of VDU (TV or computer). Embryonic mortality was evaluated in three independent experiments. Young chickens were immunized three times by porcine thyroglobulin (Tg). Blood samples were assayed after each immunization for specific anti-Tg antibodies (IgG), plasma corticosterone (CORT), and plasma melatonin (MLT). In the sham-exposed samples, embryonic death (10-33%) was restricted to the perinatal period and the IgG, CORT, and MLT responses of young chickens crested after the second immunization. Constant EMF exposure was accompanied by significantly increased fetal loss (47-68%) and markedly depressed levels of circulating anti-Tg IgG, CORT, and MLT. Collectively, these findings indicate that continuous exposure to EMFs, issuing from VDUs, adversely affects embryos and young chickens.