Platelet-activating factor in cardiovascular stress situations

Since the elucidation of its chemical structure two decades ago, platelet-activating factor (PAF) has emerged as an important mediator of various cardiovascular stress situations. Most notably, PAF was implicated as a key factor in the septic shock syndrome, based on the similarities between endotoxin and PAF biological effects, the elevation of circulating and tissue levels of PAF during endotoxemia, and the protective effect of PAF antagonists in the septic state. In addition, accumulating data suggest the involvement of PAF in the pathophysiological processes associated with ischemia, hemorrhage and trauma, where PAF exerts its effects directly on cells and blood elements or indirectly through interactions with other mediators such as cytokines and prostaglandins. Nevertheless, the relative contribution of PAF to the pathophysiological processes in endotoxemia is still unknown and should await further investigations. The primary aims of this chapter are: to delineate the effects of PAF on the cardiovascular system, to summarize the data which suggest the involvement of PAF in stress situations of the cardiovascular system, and to identify areas where future experimental efforts should be focused. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Aggressive behavior among Israeli elementary school students and associated emotional/behavioral problems and self-control.

This study aimed to identify aggression patterns among students, compare teachers' and students' reports on aggressiveness, and examine whether emotional and behavioral problems and self-control intercorrelate with aggression and can explain it among students. The study investigated 363 students aged 8 to 11 years and their 12 homeroom teachers in two elementary schools in central Israel. As expected, students reported higher verbal aggression than physical without gender differences in the general tendency. Also, students reported a higher rate of others' aggression toward them than their own aggression toward others. Similarities emerged between students' and teachers' reports. Four types of students were classified: the aggressive initiator (proactive), the aggressive responder (reactive), the passive victim, and a neutral type. An important outcome was the significant negative association of aggressiveness with self-control. Students with higher rates of self-control skills presented lower rates of aggressive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Capacitance voltage characterization of poly SiSiO2Si structures

The high frequency C-V characteristics of poly SiSiO₂Si capacitors have been studied. It is shown that the poly SiSiO₂Si capacitor C-V characteristics are significantly different from the corresponding metal-SiO₂Si capacitor due to field penetration into the poly Si layer. A comparison of the theoretical and measured C-V characteristics gives an estimate of the surface state charge density at the poly SiSiO₂ interface and indicates that the surface potential behavior of this interface is trap and surface state dominated up to poly silicon impurity concentrations of approximately 10¹⁷ cm^?3.     

Laser annealing effects on the electrical characteristics of SOS transistors

Successful incorporation of laser annealing techniques into standard processing methods requires that the electrical characteristics of the devices not be degraded. In this work, a range of energy densities from pulsed u.v. and visible lasers which can be utilized in silicon on sapphire (SOS) technology to improve device performance without introducing any deleterious side effects is determined experimentally. Silicon islands were photolithographically defined and chemically etched (KOH) on standard SOS wafers which were subsequently exposed to pulsed (25 nsec) ruby ($\text{λ = 6943}\text{A}\text{?}$) and excimer ($\text{λ = 2490}\text{A}\text{?}$) laser radiation. Comparative studies of the effect of front and back side (through the sapphire) irradiation of the silicon on device performance were conducted. Using standard processing techniques, MOS transistors were fabricated after laser irradiation and electrically characterized. It was found that under certain conditions utilization of lasers in SOS processing, can result in an increase in the interface state density at both the top 〈100〉 Si-SiO₂ interface and the bottom Al₂O₃-Si interface. However, a set of conditions exists, in which it is possible to apply laser annealing to standard SOS processing so as to increase MOS/SOS transistor channel mobility by over 30% without causing any degradation of the device electrical characteristics.     

嵌入型量测设备及封闭式控制回路在提升研磨制程能力的应用

诺威量测为第一家首先提出嵌入式量测解决方案的公司,凭借其在嵌入式量测及先进制程控制所取得的经验,提供在化学机械研磨制程上降低生产成本且可提高产品质量的测量系统。探讨嵌入型量测的观念及原理,封闭式回路控制在芯片生产上已被应用多年。     

New doxorubicin nanoparticles engineered from calcium-crosslinked carbomer and a microemulsion precursor

Abstract

The purpose of this study was to investigate a new polymeric system and production process in which self-assembled doxorubicin-loaded nanoparticles were synthetized by using a water-in-oil microemulsion as a template and calcium ions as cross-linkers. The manufacturing process combined cross-linking of carbomer within a W/O microemulsion followed by a phase-separation technique to avoid using organic solvents for extraction. To assess the sustained release behavior of doxorubicin from the nanoparticles, we have developed a new simple method based on the permeability coefficient of a synthetic membrane mounted on Franz diffusion cell system. Franz cells were preferred over the commonly used dialysis tubing because they provide adequate measures of the diffusion area as well as the volumes of the media in both sides of the membrane. The lower permeability values obtained for nanoparticles have shown that the release is a limiting step of the diffusion process, while the calculated straight lines may imply that the apparent release rate of the nanoparticle ensembles is close to a zero-order kinetics. The new drug release method for the evaluation of nano-carriers, utilizing a simple linear model to determine the permeability coefficient, has been proposed for perfect sink and non-sink conditions.     

Cardiovascular effects of platelet-activating factor

Sudden release of platelet-activating factor (PAF) into the circulation can cause hypotension, tachycardia, and circulatory collapse. To further examine this response, we performed detailed studies of cardiovascular function after PAF administration to young domestic pigs and newborn piglets. Our results indicate that circulatory dysfunction after PAF reflects severe constriction of pulmonary resistance vessels and consequent acute right ventricular failure. Although PAF-induced coronary artery constriction and contractile depression may be complicating problems, left ventricular underperfusion and dysfunction after PAF are mainly the result of systemic arterial hypotension and diminished left ventricular filling. The adverse hemodynamic effects of PAF are accompanied by substantial release of thromboxane A₂ (TxA₂). These effects are mimicked by the TxA₂ agonist U-46619 and partially blocked by specific and nonspecific inhibitors of TxA₂ synthesis (OKY-046 and indomethacin). Even more potent blockade of PAF action is exerted by the TxA₂ receptor blocker, SQ 29,548. Taken together, these findings indicate that severe pulmonary vascular constriction and hemodynamic collapse soon after intravenous PAF are at least partially mediated by PAF-induced TxA₂ release. Tachyphylaxis to PAF influence has been observed in studies of leukocyte and platelet function. We hypothesized that tachyphylaxis to PAF might also occur in our studies of constrictor responses in pulmonary vessels. Recently, we have examined the capacity of PAF to produce sustained pulmonary vasoconstriction in openchested, anesthetized newborn piglets. Infusions sufficient to produce 100% increase in mean pulmonary artery pressure after 3 min showed no loss of efficacy when sustained for 30 min. The same was true for infusions of U-46619. Thus, the pulmonary vasoconstrictor influence of PAF or U-46619 is not readily diminished by tachyphylaxis. These findings favor the viewpoint that PAF or TxA₂ release during inflammatory processes could have prolonged adverse actions on pulmonary and systemic circulations. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989. The opinions or assertions contained here are those of the authors. They do not reflect the views of the Department of Defense or the Uniformed Services University of the Health Sciences. The experiments reported here were conducted according to the principles set forth in the “Guide for the Care and Use of Laboratory Animals,” Institute of Laboratory Animal Resources, U.S. Department of Health and Human Services (NIH Publ. 85-23, 1985).