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Biomedical subjects

D E Parker

Publications and source records attributed to D E Parker.

10 recordsLinked to original sources
PubMed1979

Self-motion magnitude estimation during linear oscillation: changes with head orientation and following fatigue.

Two types of experiments concerning estimated magnitude of self-motion during exposure to linear oscillation on a parallel swing are described in this paper. Experiment I examined changes in magnitude estimation as a function of variation of the subject's head orientation, and Experiments II a, II b, and II c assessed changes in magnitude estimation performance following exposure to sustained, "intense" linear oscillation (fatigue-inducing stimulation). The subjects' performance was summarized employing Stevens' power law (R = k . Sn, where R is perceived self-motion magnitude, k is a constant, S is amplitude of linear oscillation, and n is an exponent). The results of Experiment I indicated that the exponents, n, for the magnitude estimation functions varied with head orientation and were greatest when the head was oriented 135 degrees off the vertical. In Experiments II a-c, the magnitude estimation function exponents were increased following fatigue. Both types of experiments suggest ways in which the vestibular system's contribution to a spatial orientation perceptual system may vary. This variability may be a contributing factor to the development of pilot/astronaut disorientation and may also be implicated in the occurrence of motion sickness.

Acceleration↗
PubMed1978

Visual-field displacements in human beings evoked by accoustical transients.

Sixty-two of 133 subjects reported visual-field displacements when they were exposed to intense (125 dB SPL) repetitive audiofrequency transients. This phenomenon was investigated in three experiments. Frequency (100-5000 Hz) was varied in experiment I; repetition rate (0.5/s--6.0/s) was varied in experiment II; acoustical transient onset/offset time (0.2--25 ms) was examined in experiment III. The results of these three experiments indicated that the largest proportion of displacement reports and the largest perceived motion magnitudes followed stimulation in the 500- to 1000-Hz frequency range at repetition rates of about 1/s. Response differences as a function of onset/offset time were erratic. The pattern of results obtained in this study, in conjunction with the results of previous investigations of acoustical vestibular stimulation, suggests that the visual-field displacments resulted from stimulation of the receptors of the vestibular system. These experiments may account for discrepancies in reports of infrasound-evoked eye movements. Finally, it is suggested that intense sound exposure may damage the vestibular receptors with or without concomitant damage to the auditory portion of the membranous labyrinth.

Acoustic Stimulation↗
PubMed1977

Labyrinth and cerebral-spinal fluid pressure changes in guinea pigs and monkeys during simulated zero G.

This study was undertaken to explore the hypothesis that shifts of body fluids from the legs and torso toward the head contribute to the motion sickness experienced by astronauts and cosmonauts. The shifts in body fluids observed during zero-G exposure were simulated by elevating guinea pigs' and monkeys' torsos and hindquarters. Cerebral-spinal fluid pressure was recorded from a transducer located in a brain ventricle; labyrinth fluid pressure was recorded from a pipette cemented in a hole in a semicircular canal. An anticipated divergence in cerebral-spinal fluid pressure and labyrinth fluid pressure during torso elevation was not observed. The results of this study do not support a fluid shift mechanism of zero-G-induced motion sickness. However, a more complete test of the fluid shift mechanism would be obtained if endolymph and perilymph pressure changes were determined separately; we have been unable to perform this test to date.

Animals↗
PubMed1976

The influence of sequential chemotherapy and radiotherapy on mitogen-induced lymphocyte transformation in patients with acute lymphoblastic leukemia.

Although these studies do not allow a definitive differentiation between the relative influence of chemotherapy and radiotherapy on mitogen-induced lymphocyte transformation, the data suggested both radiotherapy and chemotherapy can cause depression; however, radiotherapy may have a more pronounced effect. The relationship between the absolute peripheral blood lymphocyte count and phytohemagglutin and pokeweed mitogen-induced lymphocyte transformation was also analyzed. These data revealed that patients who are receiving or who have received intensive therapy may have normal peripheral absolute lymphocyte counts with impaired lymphocyte transformation. Serial studies of lymphocyte transformation were evaluated in 10 children with acute lymphoblastic leukemia who received both chemotherapy and radiotherapy.

Child↗
PubMed1975

Lymphocyte transformation in leukemic serum.

Cultures of normal lymphocytes were induced to transform by pokeweed mitogen (PWM). Inhibition of transformation was observed when these cultures contained sera isolated from children with acute lymphoblastic leukemia (ALL). The inhibition of transformation of normal lymphocytes was best demonstrated when the concentration of the leukemic serum in the culture medium was relatively high (60 percent); however, the inhibition was also observed with a more standard serum concentration (20 percent). Not all leukemic sera were inhibitory. Pretreatment sera from newly diagnosed patients with leukocyte counts greater than 50,000/mm3 were significantly inhibitory. Pretreatment sera from newly diagnosed patients with leukocyte counts less than 50,000/mm3, and sera from patients in remission or relapse had no significant effect. The inhibition observed with the sera of the high leukocyte count group was not believed to be related to cytotoxicity. The significance of this inhibitor in relation to clinical prognosis needs to be investigated.

Child↗
PubMed1975

Significance of serum amylase level in evaluating pancreatic trauma.

A series of fifty-one patients who underwent exploratory laparotomy for blunt abdominal trauma is reviewed. Attempts to correlate preoperative serum amylase levels with pancreatic injury were unsuccessful. We could find no statistically significant correlation between elevated serum amylase and pancreatic injury. The accuracy of the test improved somewhat with markedly abnormal serum amylase levels (greater than 300 Somogyi units/100 ml), but even at these levels the correlation was not significant. One must conclude that there is no correlation between elevated serum amylase and pancreatic injury in blunt abdominal trauma. Decisions as to the advisability of operation in patients with such trauma should therefore be based on other parameters.

Abdominal Injuries↗