Cold-dependent activation of complement: Recognition, assessment, and mechanism

Cold-dependent activation of complement (CDAC) is a phenomenon characterized by low hemolytic complement activity in chilled serum. Complement component levels are normal when measured immunologically, and there is normal hemolytic activity in EDTA plasma or serum maintained at 37°C. Little attention has been paid to CDAC except in Japan, and current unfamiliarity with it, even by clinical immunologists, can lead to confusion and unnecessary laboratory tests. A 66-year-old patient with a complex medical history is described whose complement tests showed abnormalities characteristic of CDAC. Evidence for classical complement pathway activation in the cold was obtained by CH 50 measurements, by hemolytic C4 determinations, by C4a, C3a, and C4d generation, and by quantitating complexes. A good correlation was observed among these parameters. Cryoprecipitates were absent. CDAC activity has persisted for over 5 years and is greater at 13 than at 4°C. Activation is ablated by heating at 56°C and restored by the addition of C1 to the heated serum. Adsorption by streptococcal protein G-Sepharose and precipitation by 2.5% polyethylene glycol support the hypothesis that CDAC is caused by aggregated IgG. The CDAC factor(s) also induces complement activation in normal serum but has not interfered with Raji cell or C1q binding tests or with FACS analysis. More limited studies of a second individual experiencing CDAC yielded similar results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44843/1/10875_2004_Article_BF00920794.pd

Nonvalvular atrial fibrillation as a prognostic factor in cerebral infarction

To evaluate the influence of nonvalvular atrial fibrillation (NVAF) on mortality, functional prognosis and recurrent stroke after first cerebral infarction, 141 cerebral infarction patients without valvular heart disease, which comprised 37 patients with atrial fibrillation, that is NVAF, and 104 patients without atrial fibrillation, were followed without anticoagulant therapy throughout hospitalization. Patients with NVAF were more likely than patients without AF to; have large size of cortical infarction (p < 0.01), present with a depressed mental status (p < 0.01), and develop early recurrence of stroke (p < 0.05). These led to significantly greater rates of mortality (p < 0.001) and some types of serious morbidity (p < 0.01). Age was the primary predictor of mortality in patients without AF, but had no impact on survival in patients with NVAF. Infarct size exerted the greatest influence on mortality and functional status of survivors in patient with NVAF

Effects of Counterface Surface Roughness on Friction and Wear of PEEK Materials under Oil-Lubricated Conditions

The effects of counterface surface roughness on the friction and wear behaviors of polyether ether ketone (PEEK) are studied using blocks on a ring wear tester under oil-lubricated conditions. The blocks are made of unfilled PEEK and a PEEK composite that is 30 wt% carbon fiber. The ring is made of forged steel (SF540A) and its surface roughness varies between 0.04 to 1.86 &mu;m Ra; the sliding velocity and load are 10.2 m/s and 588 N, respectively. Results indicate that both the friction coefficient and each block&rsquo;s specific wear rate increase from low to high values when the ring&rsquo;s surface roughness exceeds a certain value (0.2&ndash;0.4 &mu;m Ra). In high friction and wear regions, significant differences exist in the friction and wear behaviors of both PEEK and the PEEK composite. The PEEK composite shows a significantly lower friction coefficient and wear rate as compared to PEEK. However, the PEEK composite causes greater wear of the ring, though the extent to which the ring wears is dependent on the ring&rsquo;s surface roughness. Wear particles and wear scars on both materials are observed and analyzed using a scanning electron microscope and an energy-dispersive X-ray spectroscope. The wear mechanisms are then discussed

Wear Debris Analysis of Seizure Behaviors of PEEK Materials in Oil

Seizure behaviors of PEEK materials are studied using blocks on a ring wear tester under oil-lubricated conditions. The seizure processes are monitored with a particle counter to measure the number of wear particles in oil. Three kinds of block materials are tested: PEEK, PEEK composite filled with 30 mass% of carbon fiber, and white metal (WJ2). The ring is made of forged steel (SF540A). The sliding velocity is 15 and 19 m/s. The load varies between 294 and 1177 N. The ring temperature is measured with an alumel-chromel thermo-couple with a diameter of 0.5 mm, located 1mm below the frictional surface. Results indicate that the particle counter method can detect the seizure in the PEEK materials as well as in WJ2. However, the number of wear particle generated in the seizure of the PEEK materials is much less than in WJ2. It also increases in a mixed lubrication in WJ2. In contrast, wear particle is not detected appreciably in a mixed lubrication in the PEEK materials. Wear particles and wear scars on these materials are observed using a scanning electron microscope (SEM). The wear mechanisms in the seizure are discussed