Different breathing patterns in healthy and asthmatic children: responses to an arithmetic task.

UNLABELLED: Asthma patients have been reported to be sensitive to breathlessness, independent of the degree of airway obstruction. Paying attention and task performance may induce changes in breathing pattern and these in turn may mediate such a feeling. The present experiment investigates whether strained breathing induced by an arithmetic task was different in children with asthma compared to healthy children. METHODS: Seven healthy and eight asthmatic but symptom-free school children were equipped with electrodes for surface electromyographic (EMG) measurements of diaphragm, abdominal and intercostal (IC) muscles and with a strain gauge to monitor the pattern of breathing at rest and during an arithmetic task. The relative duration of exhalation and the relative speed of exhalation are used as measures of straining. The phase angle of maximal respiratory muscle activities relative to the maximal chest extension (MCE) are additional discriminating parameters. RESULTS: Asthmatic children breathed more slowly and already at rest the phase of their respiratory muscle activity appears to be different. While in healthy children the maximal activity of the (left)abdominal muscles occurred 5+/-29% later than the MCE, in children with asthma the maximal activity occurred 26+/-30% of the cycle earlier than MCE. In children with asthma the activity of the IC muscles starts weaning already at 10+/-30% before MCE, in contrast to the healthy children in which intercostal muscle weaning starts only at 1+/-24% after MCE. During arithmetic, the significant difference between the groups in this respect disappeared. CONCLUSION: Children with asthma show, even at rest, signs of respiratory muscle straining, probably in order to keep close control over the airflow in a similar way as healthy children during mental tasks. Such a 'careful' breathing pattern may work to prevent airway irritation also when they are free of symptoms.

Visualisation of intramural coronary vasculature by an imaging cryomicrotome suggests compartmentalisation of myocardial perfusion areas.

A technique is presented for the 3D visualisation of the coronary arterial tree using an imaging cryomicrotome. After the coronary circulation of the excised heart was filled with a fluorescent plastic, the heart was frozen and mounted in the cryomicrotome. The heart was then sliced serially, with a slice thickness of 40 microm, and digital images were taken from each cutting plane of the remaining bulk material using appropriate excitation and emission filters. Using maximum intensity projections over a series of images in the cutting plane and perpendicular plane, the structural organisation of intramural vessels was visualised in the present study. The branching end in the smallest visible vessels, which define tissue areas that are well delineated from each other by 1-2 mm wide bands populated only by vessels less than 40 microm in diameter. The technique presented here allows further quantification in the future of the 3D structure of the coronary arterial tree by image analysis techniques.

Social stress induced pressure breathing and consequent blood pressure oscillation.

A large amplitude blood pressure oscillation occurs during social defeat in a territorial fight between male rats, and during the application of a psychosocial stimulus associated with this defeat. Synchronous recording of blood pressure, intrathoracic pressure and diaphragm activity shows that the blood pressure oscillation coincides with a typical respiratory pattern called 'pressure breathing', during which a strongly positive intrathoracic pressure with expiration can be observed. The expiration was relatively prolonged and accompanied by a rise in blood pressure and a decrease in heart frequency. These alterations outlast the applied social respectively psychosocial stimulations. The results of this study suggest that behaviorally induced pressure breathing is of importance to attentional processes during social stimulation. The contribution to the development of hypertension is discussed.

Acute and conditioned blood pressure changes in relation to social and psychosocial stimuli in rats.

The naturally occurring tendency to compete with other rats for territorial space has been used to study individual behavior characteristics and blood pressure reactivity to social stimuli in adult male TMD-S3 rats. The competitive characteristics of the individual rats are consistent in two different social situations (victory and defeat). Blood pressure responses during the victory of home territory rats over intruders was more pronounced in the more competitive animals. In addition to defeat by a trained fighter rat, the experimentals were also psychosocially stimulated by the fighter while it was confined in a small wire mesh cage. The blood pressure response to this event was enhanced by the prior defeat of the test animal by the one now confined to the small cage. This response was more pronounced in competitive rats. This approach has potential as an animal model of etiological processes in socially induced hypertension.

Individual characteristics of behavior, blood pressure, and adrenal hormones in colony rats.

Previous experiments suggested that rats with an active behavioral strategy and high endocrine and blood pressure responses to social interactions would be at risk to get a high blood pressure. To test this hypothesis, a long-term study of social behavior was performed in laboratory colonies of rats. The more aggressive rats, as indicated by individual precolony resident-intruder tests, are more aggressive in the colony also. After colony aggregation, the aggressive rats appeared to have higher resting blood pressures. The dominant rat (although aggressive, too) and the nonaggressive rats have lower blood pressures. Plasma levels of catecholamines and corticosterone after colony experience do not show a relation with blood pressure but reflect the rat's original precolony aggressive characteristic. We conclude that the individual characteristic of an active social strategy is a risk factor that indeed predicts the development of high blood pressure, possibly by way of the associated higher physiological reactivity we found earlier. Chronic environmental factors that are hard to control for the animal, like involvement in social processes or possibly other continuous challenges, may stimulate the prone physiology to develop an elevation of blood pressure.

A coherent pattern among social behavior, blood pressure, corticosterone and catecholamine measures in individual male rats.

Behavioral and physiological responses of 18 chronically cannulated male TMD-S3 rats were assessed during various social interactions with conspecifics, both with and without the possibility for physical contact (social vs. psychosocial stimulation). Response magnitudes (behavior, blood pressure, plasma catecholamines) depend upon both the social environmental requirements (offense, defense, psychosocial stimulus following defense) and individual characteristics. The more competitive males generally reacted with higher responses of blood pressure and catecholamines than more passive rats. In addition, these competitive males had higher baseline levels of noradrenaline. The present experiment shows that male rats differ in the individual sympathetic tone and reactivity in relation to their behavior in a social environment.

Pair-housing of male and female rats during chronic stress exposure results in gender-specific behavioral responses.

UNLABELLED: Social support has a positive influence on the course of a depression and social housing of rats could provide an animal model for studying the neurobiological mechanisms of social support. Male and female rats were subjected to chronic footshock stress for 3 weeks and pair-housing of rats was used to mimic social support. Rats were isolated or housed with a partner of the opposite sex. A plastic tube was placed in each cage and subsequently used as a 'safe' area in an open field test. Time spent in the tube was used as a measurement of anxiety levels. Chronic stress increased adrenal weights in all groups, except for isolated females who showed adrenal hypertrophy in control conditions. In isolated males, chronic stress resulted in an increase in the time the animals spent in the tube. While stress did not affect this parameter in socially housed males, males with a stressed partner showed a similar response as isolated stressed males. Even though adrenal weights showed that isolated females were more affected by stress, after chronic stress exposure, they spent less time in the tube than socially housed females. Socially housed stressed females spent less time in the 'safe' tube compared to control counterparts, indicating that stress has a gender-specific behavioral effect. IN CONCLUSION: pair-housing had a stress-reducing effect on behavior in males. Isolation of females was stressful by itself. Pair housing of females was not able to prevent stress-induced behavioral changes completely, but appeared to reduce the effects of chronic stress.

The psychobiology of strained breathing and its cardiovascular implications: a functional system review.

Strained breathing is a natural respiratory pattern, with cardiovascular implications. It is associated with social factors, attention, expectation, and anxiety and with defense behavior in animals. An inhibition of active behavior is characteristic. Strained breathing is based on the functional heterogeneity of the medullary postinspiratory neurons. In stressful circumstances, muscle tension and laryngeal reflexes induce a strong reduction of airflow in the glottis, resulting in a prolonged Stage I of expiration and an elevated intrathoracic pressure. The resulting elevations of blood pressure and CO2 level further stimulate the strained breathing pattern. The straining factor intrathoracic pressure is an important psychophysiological parameter. Functional aspects of strained breathing may be an elevated brain perfusion and the prevention of hyperventilation. It induces blood pressure oscillations and respiratory sinus arrhythmia. Frequent strained breathing may contribute to cardiovascular pathology and sleep apnea, creating a link between functional behavior and disease.