Acta physiologica Scandinavica. Supplementum最新文献

Human hypertension is the end result of a number of genetic and environmental influences, and typically develops gradually over many years. The sympathetic nervous system appears to play a role in the early stages, with structural changes in the resistance vessels becoming dominant later on. The extent to which increased sympathetic actively may be the result of environmental stress is uncertain. Animal studies have suggested that chronic stress can raise blood pressure. Human epidemiological studies have shown that the prevalence of hypertension is strongly dependent on social and cultural factors. Blood pressure tends to be highest at work, and studies using ambulatory monitoring have shown that occupational stress, measured as job strain, can raise blood pressure in men, but not women. This may be associated with increased left ventricular mass. The diurnal blood pressure pattern in men with high strain jobs shows a persistent elevation throughout the day and night, which is consistent with the hypothesis that job strain is a causal factor in the development of human hypertension.

The paravertebral muscles (PM) act together with the hamstrings and calf muscles as important postural muscles. Both the histochemistry, biochemistry, strength and endurance of the PM were studied. Moreover attention was drawn to the exposure of PM, in particular the internal exposure level but to a certain degree repetitiveness and duration, in various job elements, and their various physiological acute responses. The thesis also deal with possible relations between the function of the PM and the magnitude of low-back trouble (LBP), and if PM muscle fatigue may play a role as a mediating factor for the occurrence of work related LBP. The lumbar PM is dominated by relatively small ST fibers with a well-developed network of capillaries, especially distinct in the central sections of PM (lumbar longissimus muscle) in females. It is remarkable that ST fibers are of the same size or larger compared to the FT fibers even in well-trained subjects. Further on PM is characterized by high activity levels of enzymes, oxidative as well as non-oxidative, important for the resynthesis of ATP and CrP. Also the level of muscles glycogen concentration is high. Altogether the PM have seemingly a potential for different metabolic pathways which may be selectively activated for a given activity. The average trunk extensor MVC varies in the different studies from 194-342 Nm and 252-450 Nm in females and males respectively. This is in accordance with predictions based specific strength, muscle cross sections and lever arms from the literature. The large range in strength due to dimension, age and training have to be considered when such data are used for e.g. ergonomic standardization and biomechanical modelling. The sex difference is smaller (female:male trunk extensor strength ratio = 0.7-0.8) than reported earlier. The small age reduction (25-60 year) of the trunk extensor strength, 0.5% per year, is probably caused by the fact that the ST dominated musculature is less sensitive to atrophy. The results indicate that a secular reduction of the trunk extensor strength has occurred during the last 2-3 decades possibly caused by a more sedentary lifestyle, both in working life due to mechanization introduced gradually during that period, and in leisure time activity. An important finding is that the static endurance time is significantly larger in the trunk extensors compared to other muscles, and larger in females than males. Possible explanations for the findings include 1) the reported histo- and biochemical results, 2) favorable blood flow conditions and 3) specific activation strategies of the muscles constituting the PM. In the vocational studies manifest signs of fatigue in the lumbar paravertebral muscles, are seen, including changes in both the energy spectra of the surface EMG towards lower frequencies and increases in the RMS amplitude, reduction of the static endurance time, and increase in the rate of perceived exertion during a working day in brick

Twenty-five hundred years ago, Hippocrates, recognizing the impact of life experience on health wrote: "those things which one has been accustomed to for a long time, although worse than things to which one is not accustomed, usually give less disturbance" (Bruhn & Wolf 1978). Since Hippocrates, much evidence has emerged to suggest that social stability is conducive to health, while social change, especially rapid change, may predispose to illness. The idea that sensory information from ordinary life experiences contributes in a major way to shaping the activities of the brain, took root in the 18th century with Pierre Gassendi and John Locke. A mechanism whereby the vast numbers of neurons in the brain could be rapidly rearranged and organized to respond to a host of different external stimuli emerged from the work of Santiago Ramon y Cajal who discovered the axonal growth cone and its capacity to elongate and guide an axon a considerable distance to a target dendrite (Cajal 1890). Thereby, with very rapid shifts in attention and perception, a wide range of responses, emotional, and physiological can be elicited. With this and other evidence at hand that the intracranial regulatory mechanisms can reorganize in response to environmental change including social change, we undertook a 30 year (1962-1992) prospective study of the effects of social patterns on health in Roseto, a closely knit Italian-American incorporated town in Pennsylvania. It was settled in 1882 by Italians from Roseto val Fortore, a town in southern Italy near the Adriatic Sea. We found a sharp increase in myocardial infarction among Rosetans when long established cohesive social patterns began to weaken and be replaced by more egocentric attitudes.

In addition to repeated reexperiencing of the event, the delayed effects of severe psychological trauma, i.e., post traumatic stress disorder (PTSD), present a paradoxical mix of symptoms. There is enhancement of the self-preservative catecholamine states; anger and fear with a contrasting sense of meaninglessness and blunting of the emotional responses of the attachment behavior so critical for species preservation. Hormonally, there is a striking separation of the catecholamine response, which stays elevated and that of the hypothalamo-pituitary-adrenal (HPA) axis, which may remain at normal levels. Pathophysiologically, the reexperienceing of the trauma and the arousal may be associated with dysfunction of the locus coeruleus, amygdala and hippocampal systems. This article explores the consequences of an additional dysfunction: a dissociation of the hemispheres that appears to be responsible for the alexithymic avoidance and failure of the cortisol response that so often follow severe psychological trauma. There is neurophysiological evidence that the left the right hemispheres subserve different emotional sets that correspond to "control" and "appraisal," i.e., very approximately to the self and species preservative behavioral complexes, respectively. Several studies point to physiological dissociation of hemispheric functions during alexithymia. This raises the question: What has been lost if in this condition the right side no longer fully contributes to integrated cerebral function? Right hemispheric damaged children lose critical social skills and in adults the related sense of familiarity critical for bonding is lost. Such losses of social sensibilities may account for the lack of empathy and difficulties with bonding found in sociopathy and borderline personality: conditions now believed to result from repeated psychological trauma during development. On the other hand, systems that promote right hemispheric contributions provide solacing access to a "Higher Power." They also appear to protect against socially disordered behavior, substance abuse, the failure of the HPA axis and some aspects of the pathophysiology of chronic disease.

The interactive etiological and pathogenic processes between physical and psychosocial environ-mental stimuli, the individual's appraisal of these influences, and his or her reactions to them in terms of emotion, cognition, behaviour, and physiology; the modification of these reactions through coping, social support, and other interacting variables; and the resulting changes in health and well-being--are extremely complex and poorly understood. Against this background, this paper argues for a biopsychosocial approach, based on an ecological model influenced by, and influencing, James P. Henry's related approaches. This approach is exemplified in six studies carried out by our group and briefly reviewed in this paper.

In the wild, tree shrews (Tupaia belangeri) live in pairs in territories which they defend vigorously against strange conspecifics. The paper gives an overview on some of our laboratory studies with tree shrews, which demonstrate the great relevance the concepts of Jim Henry have in understanding the biological relevance of mammalian social behavior. A basic result of these studies is that the physiological consequences of social relations between mammals depend on the appraisal of the situation by the animals and their coping behavior. Appraisal of a stimulus or a situation, as well as the resulting coping behavior, are basically psychological processes. There are, therefore, no simple relationships between stimuli imposed on individuals and their physiological responses; rather the behavioral, psychological and, thus, the physiological responses of individuals to stimuli differ depending on their genetics, prenatal influences and postnatal learning processes. This means, to understand the consequences of social relations between individuals, an integrated approach is required to assess which factors, including social rank and bonds to conspecifics, interact to affect an individual's fertility and health, as has been so clearly demonstrated in the work of Jim Henry.

By means of tele-receptor signals (vision, hearing, olfaction) the mammalian brain is almost continuously informed about environmental events, and whenever these are interpreted as positive or negative challenges the cerebral "super-controller" can, for coping with the anticipated situation, select the most appropriate among a number of pre-formed hypothalamic reaction patterns. These are organized as combined engagements of the somatomotor, visceromotor and hormonal efferent links, whereby a variety of behavioural responses can be elicited, where each is accompanied by appropriate adjustments of inner organ systems, metabolism, etc., to achieve optimal performance. For eons of time these "emotionally charged" reactions, common for all mammals, have served to protect the individual and species in a merciless environment, and they certainly remain principally the same also when Homo Sapiens faces modern society. As then the ancient "defence" and "defeat" reactions, intended for quite different situations, are often activated by the many artificial stimuli and symbolic threats inherent in today's hectic and competitive life, their principal organisation and functional consequences are the main topic of this survey. They are, for example, also marginally engaged along with ordinary shifts in mood during events in daily-life but are probably in this mild form fairly harmless and actually often supportive for efficient performance. However, when intensely engaged over longer periods they can, indeed, profoundly disturb inner organ systems and metabolic events, often resulting in disorder and even in premature death, as particularly convincingly shown by Henry and co-workers in studies on rodent "micro-societies". Transferred to man's situation in modern life, these model studies have been crucial for insight into the indeed complex mechanisms involved when long-term psychosocial stress in predisposed or particularly exposed individual contributes to some of today's most important "disorders of civilisation".

The experimental data available today strongly indicate that various types of physiological stressors, including physical exercise and emotional stress, can influence immune function. Natural immunity represents a first line of defence in viral infections and cytotoxicity to a variety of tumour cells. Natural immunity is strongly influenced by chronic exercise and this regulation includes interaction between the nervous, endocrine and immune systems. Central mechanisms including the endogenous opioids are of great interest. Chronic activation of endogenous opioid systems augments natural cytotoxicity and the possible involvement the opioids in the exercise-induced enhancement of natural immunity is discussed. Also, catecholamines seem to play an important role in the regulation of immune function, both after chronic exercise and emotional stress. The physiological significance of the reported changes in natural cytotoxicity after exercise-training is as yet unclear.

Evidence is presented that most components of the human stress response are influenced asymmetrically by the cerebral hemispheres. The right hemisphere is endowed with a unique response system preparing the organism to deal efficiently with external challenges. Therefore, both the hypothalamic-pituitary-adrenocortical (HPA) axis and the sympathetic-adrenomedullary (SA) axis seem to be under the main control of the right hemisphere.