Biomedical subjects

E A Higgins

Publications and source records attributed to E A Higgins.

4 recordsLinked to original sources

PubMed1979

Effects of altitude and two decongestant-antihistamine preparations on physiological functions and performance.

Fourteen men were studied to determine the combined effects of two altitudes--388 and 3,810 m or 1,274 and 12,500 ft--and three preparations--lactose placebo, Compound A (Actified, and Compound B (Dristan). Subjects reported least attentiveness with A and greatest with placebo. Fatigue increased significantly with time while energy, interest, and attentiveness decreased. The Multiple Task Performance Battery (MTPB) showed no effects of altitude, drugs, or time on overall performance; however, performance declined with time in several tasks, while problem solving improved. Subjects enjoyed the problem-solving tasks and may have given them preference as levels of interest declined. Though the MTPB overall composite scores did not change significantly, physiological parameters and subjective evaluations indicate that type of compound and time after ingestion are important. Declines in energy and attentiveness 2.5 h after ingestion could result in neglect of important--although routine--tasks. Hypoxia might enhance this effect and consequences might be worse in subjects whose medical conditions require these drugs.

17-Ketosteroids↗

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↗

PubMed1977

Transient and permanent effects of hyperthermia in dogs: a study of a simulated air transport environmental stress.

Heat-induced hyperthermia can be a major problem in dogs shipped during summer months. Dogs shipped by air transport can encounter temperatures as high as 54.4 C. Usually, little concern is given to effects produced by hyperthermia. To assess the heat stress problem, 20 dogs were exposed to a temperature of 54.4 C for 30 minutes--10 dogs at 15% relative humidity and 10 dogs at 35%. Dogs did not die as a result of exposure, but certain transient and permanent changes occurred. All dogs had increased heart rate, rectal temperature, blood pH, hemoglobin concentration, packed cell volume, and erythrocyte count. Body weight and PVCO2, decreased. Differences also were shown between the 2 humidity group for blood PH PVCO2, rectal temperature, and weight loss. The major tissue changes attributed to hyperthermia were fragmentation of the myocardium, acute cortical necrosis in kidney, and marked degenerative changes in the cerebellum and cerebral cortex. Changes in the cerebellum and cerebral cortex were considered severe and permanent.

Aircraft↗

PubMedDate not supplied

Quantitation of desynchronosis.

In order to find ways of preventing or correcting the effects of desynchronosis, it is necessary to know the physiological mechanisms that are affected and to quantitatively determine their rate of recovery following a time-zone change. To best accomplish this, it is necessary not only to establish the rates of change brought about in performance and physiological systems during actual flight experiments, but to complement these observations with ground-based simulation experiments. A mathematical model was developed to quantitatively describe desynchronosis and was applied to data obtained from ground-based photoperiod shift studies using monkeys. An initial steady state, Vc, and a final steady state, Vs are postulated. The measured data vector, Vt, initially equals Vc, and finally equals Vs. The difference vector, Vts, with components A(t) and B(t), defined as the dot product and cross product of vectors Vt and Vs, is termed the desynchronosis vector. The trajectory of A(t) with time is given by: A(t) = A - e (alpha + betat), where A is the asymptote denoting complete resynchronization, alpha is proportional to the total desynchronosis on day O, and beta is the rate of resynchronization. The number of cycles required to achieve a 95% recovery, t95, is computed. This model has been applied to body temperature (BT) data from a monkey subjected to a 180 degrees phase-shift by alternating the photoperiod. The BT rhythm was initially stable and a 180 degrees reversal of phase with the new environment was eventually achieved. Estimated rephasal times were: 37% in 2.6 days; 50% in 5.6 days, and 95% in 8.4 days. Similar rates of internal and external resynchronization have been obtained from human photoperiod shift, ground-based experiments. Estimated rephasal time for BT rhythms with HR rhythms to the new photoperiod (t95) is 4.9 days.

Animals↗