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Biomedical subjects

C M Winget

Publications and source records attributed to C M Winget.

At least 19 recordsLinked to original sources
PubMed1985

Circadian rhythms and athletic performance.

Daily or circadian rhythmical oscillations occur in several physiological and behavioral functions that contribute to athletic performance. These functions include resting levels of sensory motor, perceptual, and cognitive performance and several neuromuscular, behavioral, cardiovascular, and metabolic variables. In addition, circadian rhythms have been reported in many indices of aerobic capacity, in certain physiological variables at different exercise levels, and, in a few studies, in actual athletic performance proficiency. Circadian rhythmicity in components of athletic performance can be modulated by workload, psychological stressors, motivation, "morningness/eveningness" differences, social interaction, lighting, sleep disturbances, the "postlunch dip" phenomenon, altitude, dietary constituents, gender, and age. These rhythms can significantly influence performance depending upon the time of day at which the athletic endeavor takes place. Disturbance of circadian rhythmicity resulting from transmeridian flight across several time zones can result in fatigue, malaise, sleep disturbance, gastrointestinal problems, and performance deterioration in susceptible individuals (circadian dysrhythmia or "jet-lag"). Factors influencing the degree of impairment and duration of readaptation include direction of flight, rhythm synchronizer intensity, dietary constituents and timing of meals, and individual factors such as morningness/eveningness, personality traits, and motivation. It is the intent of the authors to increase awareness of circadian rhythmic influences upon physiology and performance and to provide a scientific data base for the human circadian system so that coaches and athletes can make reasonable decisions to reduce the negative impact of jet-lag and facilitate readaptation following transmeridian travel.

Altitude↗
PubMed1984

A review of human physiological and performance changes associated with desynchronosis of biological rhythms.

This review discusses the effects, in the aerospace environment, of alterations in approximately 24-h periodicities (circadian rhythms) upon physiological and psychological functions and possible therapies for desynchronosis induced by such alterations. The consequences of circadian rhythm alteration resulting from shift work, transmeridian flight, or altered day lengths are known as desynchronosis, dysrhythmia, dyschrony, jet lag, or jet syndrome. Considerable attention is focused on the ability to operate jet aircraft and manned space vehicles. The importance of environmental cues, such as light-dark cycles, which influence physiological and psychological rhythms is discussed. A section on mathematical models is presented to enable selection and verification of appropriate preventive and corrective measures and to better understand the problem of dysrhythmia.

Adaptation, Physiological↗
PubMed1978

Biological aspects of suicide: circadian disorganization.

Disturbances in the circadian rhythmicity of biological functions have been reported in various mental disorders. Four lines of research--hormonal, electroencephalographic, cerebral spinal fluid, and circadian rhythmicity--suggest possible changes in suicidal individuals. During a study investigating the effect of a photoperiod shift on circadian rhythms, 15 male, healthy, normal subjects were used. Following a 5-day baseline period a 12-hour photoperiod shift took place and was followed by 10 days of recovery period. Multiple parameters were monitored. Two weeks following completion of the study one subject suicided. The data were examined to determine whether the suicided subject differed, rhythmically, from other subjects. Summation dials describing phase changes and vector difference dials describing dynamic phase relationships of rhythm pairs showed that the rhythms of this subject were poorly synchronized internally during baseline. Total urinary output of all parameters was lower than all other subjects during baseline and more of his urinary parameters rephased incompletely during recovery. The results suggest that circadian asynchrony and an inability to respond effectively to a phase shift may characterize a presuicidal state. These results are discussed in terms of the four lines of research involving biological aspects of suicide and suggest some intriguing interactions.

17-Hydroxycorticosteroids↗
PubMed1978

Physiological effects of rotational work shifting: a review.

The high cost of capital equipment, demands of the world markets, and continuity requirements of many technological processes have forced industry to operate three-shift, 24-hour days. Workers on fixed schedules experience no particular problems from shift work, but those who are shifted periodically can undergo physiological and emotional disturbances. These disturbances occur because most human systems function according to circadian rhythms that can be easily disoriented. The primary cause is the periodic shifting of the light-dark, wake-sleep cycles. Extensive literature exists on the cause and symptoms of disturbances in the human physiological rhythms. The information contained in this literature can be applied to protecting the health and well-being of the worker.

Accidents, Occupational↗
PubMed1977

Circadian patterns of stress-induced ACTH secretion are modified by corticosterone responses.

To test whether there is a circadian rhythm in the ACTH response to stress, young female rats were exposed to a variety of ACTH-releasing stimuli at 0600 and 1800 h and changes in circulating ACTH and corticosterone were measured. The results of these experiments suggested that after the high intensity stimuli of laparotomy with intestinal traction or 250 mug histamine ip/100 g BW, the morning ACTH response was greater than the evening response. However, the ACTH response to ip saline was greater in the evening in one experiment and greater in the morning in a second experiment. Plasma corticosterone responses were faster and greater in the morning in the first experiment and in the evening in the second experiment. The ACTH response to 125 mug histamine ip/100 g BW was greater in the evening and the change in corticosterone was greater in the morning. Thus, after low intensity stimuli, the ACTH responses appeared to depend on both the lag time prior to the corticosterone response, and its magnitude. To test this possibility, rats were adrenalectomized and the ACTH response was measured 7.5 and 15 min after the start of surgery and after injection with either 2% EtOH-saline, or 50 mug corticosterone at operation, or with 30 mug corticosterone at 5 min. Compared with ACTH levels in rats treated with vehicle, ACTH levels were decreased 7.5 min after 50 mug corticosterone at operation (P less than 0.01), but not after 30 mug corticosterone at 5 min. ACTH levels were slightly reduced 10 min after 30 mug corticosterone at 5 min compared with those of rats injected with vehicle at operation (P less than 0.05). These results are consistent with the interpretation that corticosterone secretion modifies stress-induced ACTH secretion via the fast-feedback effect. Comparison of the ACTH responses to acute adrenalectomy plus injection with EtOH-saline at 0600 and 1800 h demonstrated that, in the absence of a corticosterone response to the stress, the ACTH response is greater in the morning that in the evening (P less than 0.01). Finally, this group of experiments suggests strongly that the responsivenss of rat adrenal glands to ACTH increases markedly between 0600 and 1800 h.

Adrenalectomy↗
PubMed1976

Changes in glucose, insulin, and growth hormone levels associated with bedrest.

Changes in plasma glucose, insulin, and growth hormone (HGH) resulting from exposure to 56 d of bedrest were determined in five healthy young male subjects. Blood samples were collected by repeated venous puncture at 4-h intervals for 48-h periods before bedrest, at 10, 20, 30, 42 and 54 d after confinement to bed and at 10 and 20 d after bedrest. Changes in the daily levels of these factors for each subject were expressed as the mean of the six samples per 24-h period. The level of HGH dropped after 10 d of bedrest, then showed a 1.5-fold increase at 20 d (p less than 0.05) and subsequently decreased gradually reaching levels of 2.5 mg/ml/24 h, well below pre-bedrest controls of 4.2 mg/ml/24 h, by the 54th d. In spite of a marked increase in the daily plasma insulin levels during the first 30 d of bedrest, glucose levels remained unchanged. Beyond 30 d of bedrest, insulin began decreasing toward pre-bedrest levels and glucose followed with a similar reduction to below the control levels of 75 mg/100 ml/24 h on day 54. The daily mean changes reflect a change in the amplitude of the diurnal variation. The daily peak in plasma insulin shifted progressively to the late evening during the bedrest period.

Adult↗
PubMed1976

Psychologic and psychophysiologic response to 105 days of social isolation.

The responses of nine subjects to 105 d of social isolation are reported. The study reveals that crew selection plus ongoing support by psychiatric staff permits continued function in an exotic milieu. Prediction of psychophysiologic symptoms was possible using paper and pencil tests. Trait anxiety was altered by the isolation in a psychologically healthy direction. Sudden time shifts of 8 h led to an immediate significant increase in depression, aggression, and hostility, and are accompanied by marked increases in physical symptoms. During the first free-running phase of the experiment, significant shifts were found on four psychological measures. The shifts indicate that subjects became less trusting, more orderly, more routinized, less energetic, and more depressed. A reducer-augmenter scale predicted the number of psychophysiologic complaints reported by individual subjects while isolated. A group interaction effect on circadian rhythms was isolated but needs further examination.

Adult↗
PubMed1975

Response of mice to repeated photoperiod shifts: susceptibility to stress and barbiturates.

Three inbred strains of mice selected for their spontaneous aggressive behavior and differential susceptibility to stress were exposed to a controlled environment where on an average of once every 4 days for 76 days and subsequently on an average of once every 2 days for an additional 55 days a 12L:12D photoperiod was reversed by 180 degrees. This procedure did not affect the growth of the mice and appeared to reduce fighting. However, plasma corticosterone concentrations in all three strains of mice were high, and their response to a 24-hr cold stress was no longer evident. The most pronounced effect of the altered photoperiod was on the barbiturate-induced sleeping time which showed a 40% reduction in all strains in spite of differential suceptibility to the drug among strains. It is concluded that repeated random phase shifting by varying the photoperiod is a stressful experience to which animals do not adapt and that the ability to respond to an additional stimulus or drugs may be greatly altered.

Aggression↗