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Although epidemiological studies of the relationship between cigarette smoking and colorectal cancer risk have been equivocal, a positive association is consistently found for colorectal adenoma development. We performed an epidemiological study to determine whether p53 protein overexpression, in tumours obtained at the time of resection, is associated with cigarette exposure in colorectal cancer. A total of 163 colorectal cancer cases and 326 healthy controls responded to a standardised questionnaire on colorectal cancer risk factors including detailed information on their history of cigarette smoking. All patients' tumours were analysed immunohistochemically for p53 overexpression using an avidin-biotin immunoperoxidase procedure and polyclonal anti-p53 antibody CM1. Comparison of colorectal cases with controls revealed an elevated risk for ex-smokers (OR = 1.34, 95% CI 0.85-2.12) and current smokers (OR = 1.13, 95% CI 0.63-2.02) when compared with non-smokers. No dose-response relationship was found for total pack-years of smoking (trend test: P = 0.19). However, a trend for total pack-years of smoking was found when p53-positive cases were compared with p53-negative cases suggesting aetiological, heterogeneity (trend test: P = 0.06). Estimating the individual relative risk of developing a p53-positive tumour relative to controls showed no associations for smoking status or total pack-years of smoking. However, when p53-negative cases were compared with controls, an elevated risk was found for ex-smokers (OR = 1.84, 95% CI 1.00-3.37) and current years of smoking (trend test: P = 0.03). Colorectal tumours developing through p53-positive dependent pathways were not associated with smoking exposure. A significant increase in risk was observed for the p53-negative independent pathway with smoking. p53 overexpression appears to be associated with smoking exposure in colorectal cancer.

To examine the hypothesis that colorectal carcinomas with and without TP53 mutations may be characterised by aetiological heterogeneity, we analysed a group of 107 patients with primary Dukes' C colorectal cancer seen at the Memorial Sloan-Kettering Cancer Center (MSKCC) from 1986 to 1990. We assessed p53 overexpression using the monoclonal antibody PAb 1801, and identified 42 (39%) patients displaying p53-positive phenotype, defined as > or = 25% of positive cells. Patients with two or more first-degree relatives with cancer had an odds ratio (OR) of 2.9 (95% CI 1.0-8.3) for p53 overexpression in comparison with those without a family history of cancer (trend test, P = 0.11). A possible association between body weight and p53 overexpression was observed. The ORs were 1.9 for the second quartile, 1.9 for the third quartile and 3.4 for the highest quartile in comparison with the lowest quartile (trend test, P = 0.06). No association between occupational physical activity, smoking, drinking, parity and p53 overexpression was identified. The results suggest that p53 overexpression may be related to genetic predisposition to colorectal cancer, and p53-positive and p53-negative colorectal cancers may be controlled by different aetiological pathways.

Combinations of analog and switching techniques have led to the development of audio power amplifiers capable of producing low distortion with high efficiency. The high efficiency is achieved with a combination of an inverter and an analog amplifier, where the inverter provides the power, and the analog amplifier acts as an active filter to correct distortion. In this paper, a full analysis of the system is presented using the hysteresis describing function approach to model the inverter. The set of equations obtained allows the description of the nonlinear behavior of the system, such as the limit cycle of the output voltage and its dependency on the hysteresis. The theoretical development also provides the relation between the switching frequency and the system parameters. The derived equations are verified and compared using PSpice simulations. Index Terms--Audio amplifier, class D amplifier, describing function, high efficiency.

Small-signal Thevenin and Norton equivalent circuits seen looking into each terminal of the BJT and the FET are described. The application of these circuits to writing by inspection the expressions for gain, input resistance, and output resistance of multistage amplifiers is demonstrated. The application of the circuits to the noise analysis of devices is illustrated by the calculation of the noise input voltage and current of the BJT and the noise input voltage of the MOSFET. The circuits are useful for the analysis of feedback amplifiers where Mason's signal flow graph can be used to solve the simultaneous equations that are obtained. Several examples are presented which illustrate flow-graph solutions for feedback circuits.

Electromechanical equation analogs are used to derive piezoelectric transducers-controlled source analogous circuits. The equations are analogous to the telegraphists equations for voltage and current waves on electrical lines. The models derived are notable for the absence of transformers and negative impedance element. SPICE implementations of the derived models enable the calculation of transducer response for sinusoidal and arbitrary pulse signal inputs.

Significant adverse impact of various forms of psychological stress on susceptibility to infection, altered wound healing, increased prevalence and severity of hypersensitivity diseases, and even increased mortality in cancer patients has been well described. Yet these observations are limited by often unpredictable individual responses to various stressful situations. These associations are further clouded by natural variability among diverse forms of and responses to chronic life stressors and associated comorbid conditions. This is particularly true for inflammatory diseases where gene/external environmental interactions are well-described. What is much less understood is gene-internal environmental (i.e., psychological) interactions that commonly affect disease activity and possible susceptibility. We have used selected single nucleotide polymorphisms of stress hormone and regulatory cytokine receptors to categorize both baseline and stress-associated immune parameters for the a priori classification of individuals with the most stress susceptible immune systems to identify those most responsive to a stress reduction/management-based intervention. [ABSTRACT FROM AUTHOR]

Dentin consists of several identifiable structures: tubules with cell processes and fluid; highly mineralized peritubular dentin; and inter tubular dentin consisting mainly of collagen and deposited apatite. The structural organization and micro structural variations reflect formative influences, such as tooth ate and shape, and alterations caused by age, insult, and disease. However, details of structure-chemistry-property relationships for this anisotropic biologic composite are limited. Materials scientists are focusing on an array of new spectroscopic, analytical, and imaging techniques that are yielding improved understanding of structural variations and their dependence on specimen preparation, tooth type, location, storage conditions, and chemical and physical modifications. Such studies should lead to the major refinements in structure-properties models for dentin that are required for continued advances in dental composite resins and adhesives. [ABSTRACT FROM AUTHOR]