THE EFFECT OF HYPERTENSIVE EPISODES AND CARDIAC HYPERTROPHY ON THE CANINE CARDIAC BAROREFLEX

1. Left ventricular (LV) hypertrophy has been implicated in the reduction of baroreflex sensitivity present in hypertension. The aim of the current study was to investigate the mean arterial pressure-heart rate reflex (MAP-HR) in a model which induced left ventricular hypertrophy but no sustained blood pressure elevation. 2. Five mongrel dogs were exposed to transient blood pressure elevation of between 20 and 30 mmHg, through hindlimb compression using a pneumatic pressure suit, for 7 h per day, 6 days per week for 6 weeks. Resting blood pressure was not altered by the 6 week hindlimb compression intervention. 3. Echocardiographically determined LV mass (mean ± s.e.m.) was 116.0 ± 7.4 g prior to hindlimb compression (baseline) and elevated to 125.4 ± 8.1 g (P= 0.003) after 6 weeks of compression. A reduction in the early (E) to late (A) transmitral diastolic flow ratio (E/A) from 1.80 ± 0.06 at baseline to 1.54 ± 0.09 (P = 0.037) after the 6 week intervention suggested that cardiac compliance was reduced. 4. The maximum gain of the MAP-HR reflex, studied using the ‘steady-state’ drug technique, when blood pressure was normal, showed a trend for reduction from 3.85 ± 0.43 beats/min per mmHg at baseline to 3.10 ± 0.45 beats/min per mmHg (P= 0.067) after 6 weeks of compression. This gain reduction became significant after β-adrenoceptor blockade with propranolol (3.13 ± 0.55 vs 2.32 ± 0.25 beats/min per mmHg; P= 0.039). Covariant analysis showed a significant inverse correlation between LV mass and maximum gain (r= 0.96; P<0.001) during the 6 week compression period. 5. The MAP-HR reflex changes in this model mimic those present in hypertension and implicate cardiac hypertrophy as one possible mediator.     

Pharmacological characterization of performance on a concurrent lever pressing/feeding choice procedure: effects of dopamine antagonist,cholinomimetic, sedative and stimulant drugs

This experiment was undertaken to provide a pharmacological characterization of performance on a task involving food-related instrumental and consummatory behavior. Rats were tested in an operant chamber in which there was a choice between pressing a lever to receive a preferred food (Bioserve pellets) or approaching and consuming a less-preferred food (Lab Chow). The lever pressing schedule was a fixed ratio 5 (FR5). Rats usually pressed the lever at high rates to obtain the preferred food, and typically ate little of the lab chow even though it was freely available in the chamber concurrently with the lever pressing schedule. Previous work has shown that injection of dopamine (DA) antagonists, or depletion of DA in the nucleus accumbens, caused a substantial shift in behavior such that lever pressing was reduced but chow consumption increased. In the present study it was shown that the DA antagonist haloperidol decreased lever pressing and increased chow consumption at doses of 0.1 and 0.15 mg/kg. The D1 antagonist SCH 23390 (0.05, 0.1 and 0.15 mg/kg) and the non-selective DA antagonistcis-flupenthixol (0.3 and 0.45 mg/kg) decreased lever pressing and produced substantial increases in chow consumption. The D2 antagonist sulpiride decreased lever pressing, but produced only slight increases in chow intake at the highest dose. Pentobarbital reduced lever pressing and increased chow consumption at 10.0 mg/kg. The muscarinic agonist pilocarpine produced dose-related decreases in lever pressing, but failed to increase chow consumption. Amphetamine produced dose-related decreases in both lever pressing and chow consumption. These results indicate that low/moderate doses of the DA antagonists haloperidol,cis-flupenthixol and SCH 23390 can suppress lever pressing in doses that leave the animal directed towards food acquisition and consumption.     

Preventing accidental injury to young children in the home using volunteers

Accidental injury in the home is a major cause of death andill-health among young children. Reducing home safety hazardsby the use of safety devices such as stair barriers and safetytaps has the potential to prevent home injuries. Little is knownabout levels of home safety hazards or how to encourage parentsto reduce hazards. The Safe Place Project examined parents'knowledge of home safety and the prevalence of safety hazardsin homes where there were young children. The study also evaluatedthe effectiveness of a low-cost strategy aimed at reducing homesafety hazards. The strategy used trained volunteers to providehome safety checks and tailored safety education in conjunctionwith increasing the availability of home safety devices. Onehundred and six families with young children participated inthe project. Some homes contained many hazards, with 43% ofthe sample having more than 10 home safety hazards. At follow-up,the intervention group showed a significant reduction in homehazards and a trend towards an increase in knowledge of homesafety.     

A decomposition approach to suboptimal control of discrete-time systems

A suboptimal controller for a class of discrete-time systems is presented. The controller is derived by first solving ‘off-line’ a simplified optimal control problem obtained by neglecting part of the system state and by considering a larger time step, then by solving ‘on-line’ at each time step an optimization problem based on the results of the previously solved ‘off-line’ problem. A simple numerical example is presented to illustrate the control scheme.     

河南省地方性高碘甲状腺肿的发现、流行特征及其干预研究

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Mixed h2 and h∞ optimal robust control design

This paper introduces a design methodology for a dynamic compensator that simultaneously minimizes the upper bound of a quadratic performance index and the H_∞-norm of a disturbance transfer function matrix of a multiple-input/multiple-output system whose model contains parameter uncertainty in the state and input matrices. The real parameter uncertainty is modelled as additional measurement outputs and as additional weights on the existing noise inputs and measurement outputs of the system. The compensator equations are derived by taking the dual of a system with parameter variation in the state and output matrices, for which the compensator equations have previously been derived, and then taking the dual of the compensator equations. An algorithm for applying this theory is given and an example is shown.     

Victim Help Seeking: Differences Between Intimate Terrorism and Situational Couple Violence

Abstract: Research indicates that two major forms of partner violence exist, intimate terrorism (IT) and situational couple violence (SCV). The current study (N= 389) used a subgroup of women who responded to the Chicago Women’s Health Risk Study to examine whether type of violence experienced is differentially related to formal (e.g., police, medical agencies, counseling) and informal (e.g., family, friends/neighbors) help seeking. IT victims were more likely to seek each type of formal help but were equally or less likely to seek informal help. Findings can inform both family violence research and the development and implementation of social service programs.     

中心流形定理在非线性动力学系统分析和控制中的应用

本文将中心流形定理用于一类非线性动力学系统的局部定量分析和设计中,从而改进和简化了传统的分析和设计方法,弥补了线性化方法在处理这类系统方面的不足。