Biomedical subjects

C D Goodyear

Publications and source records attributed to C D Goodyear.

7 recordsLinked to original sources

PubMed1991

Mass discrimination under Gz acceleration.

The purpose of this study was to assess how the perception of mass discrimination is affected by elevated Gz acceleration. Previous experiments studied mass discrimination under weightless conditions. Ten subjects were tested with the Dynamic Environment Simulator (DES) at Wright-Patterson Air Force Base. Masses of 105, 110, 115, 120, and 125 g were compared to a 100-g standard for delta Ms of 5, 10, 15, 20, and 25 g. The subject had to choose which mass felt heavier. This was done at 1, 2, and 4 Gz. Significant differences were found between each of the G levels, and the subjects made more errors at higher Gz. Significant differences were also found between each of the delta Ms, except between delta Ms of 20 and 25 g. Using regression lines, the difference limen was calculated at the 75% correct response level for each Gz. The Weber fraction was found by dividing the difference limen by the 100-g standard. Weber fraction of 0.085, 0.116, and 0.145 were found at 1, 2, and 4 Gz, respectively. Impairment to discrimination was shown by calculating the ratio of the Weber fraction of the elevated Gz to 1 Gz. This demonstrated an impairment to mass discrimination at 1.36 at 2 Gz and 1.71 at 4 Gz. Impairment of mass discrimination under elevated G indicates that loss of adaptation is more important than weight or mass constancy or any other factors which would increase gravitational sensory cues. This study attempted to show adaptation by comparing runs done on different days. To show aftereffect, intervals of 1 G were compared to each other. The study did not find any adaptation or aftereffect. When compared to previous studies done in weightlessness, microgravity was found to be more detrimental to mass discrimination than macrogravity, at least up to 4 Gz.

Acceleration↗

PubMed1986

The effects of various antishock trouser inflation sequences on hemodynamics in normovolemic subjects.

In an attempt to maximize the hemodynamic effects of antishock trousers, a pair of such trousers was modified to a five-bladder trouser (one abdominal, two thigh, and two calf bladders) and inflated using three different inflation sequences. These three sequences were simultaneous inflation of all five bladders; concurrent inflation of the calf and thigh bladders and then inflation of the abdominal bladder (standard inflation); and sequential inflation of the calf, thigh, and abdominal bladders. Simultaneous inflation resulted in the greatest increase in blood pressure and the smallest increase in end-diastolic volume, stroke volume, and cardiac output. The standard inflation sequence resulted in slightly higher increases in end-diastolic volume, stroke volume, and cardiac output than the sequential inflation sequence, and a significantly larger increase in cardiac output than the simultaneous inflation sequence. Our study indicates that of the three sequences used, the standard inflation sequence produces the greatest blood return to the heart.

Adult↗

PubMed1986

Effect of dihydroergotamine on +Gz acceleration tolerance.

Dihydroergotamine is a potent vasoconstrictor of the venous capacitance vessels and has been shown to decrease blood pooling in patients with orthostatic hypotension. Acceleration acting on the long axis of the body (+Gz) pools blood into the lower body of the subject. Nine healthy men received an injection of 1 mg dihydroergotamine and 1 ml of saline intramuscularly in a randomised, double blind fashion, and had their Gz acceleration tolerances measured. Dihydroergotamine significantly increased Gz tolerance by 0.24 G and narrowed the difference between the maximum heart rate during the acceleration epoch and resting baseline by 10%. The drug had no effect on blood pressure and heart rate when the subjects changed from the supine to standing position. The increase in Gz tolerance was not sufficient for operational use.

Acceleration↗

PubMed1986

The effects of inflation of antishock trousers on hemodynamics in normovolemic subjects.

Antishock trousers may maintain mean arterial pressure in trauma patients by increasing central blood volume and cardiac output. Hemodynamics, end-diastolic volume, stroke volume, cardiac output, and blood pressure were recorded in eight supine, healthy men in antishock trousers using two-dimensional echocardiography. Two inflation protocols were used. The antishock trousers were inflated to 50 and 100 mm Hg in a random fashion and inflation was maintained for 30 minutes before deflation. End-diastolic volume and blood pressure rose significantly (p less than 0.05) after antishock trouser inflation of 50 and 100 mm Hg. With the 50 mm Hg inflation, the stroke volume and end-diastolic volume fell below baseline over time. This did not occur with the 100 mm Hg inflation. After suit deflation, the stroke volume, end-diastolic volume, and cardiac output increased with 50 mm Hg inflation. The study shows that the antishock trousers alter several hemodynamic parameters. With lower inflation pressures, antishock trousers cause an increase in arterial pressure by increasing peripheral resistance. At higher inflation pressures, the antishock trousers increase cardiac output and as the cardiovascular system adjusts, maintain the pressure by increasing peripheral resistance.

Abdomen↗

PubMed1985

Hemodynamic effects of anti-G suit inflation in a 1-G environment.

This study evaluated effects of various anti-G inflation pressures on cardiac volumes and the relationship of these volume changes to mean arterial pressure changes. Ventricular volumes were calculated using two-dimensional echocardiography. An anti-G suit was inflated to 2, 4, and 6 psi in the standing and supine positions for 10 male subjects. In the supine position, mean arterial pressure increased from base line for all three inflation pressures (P = 0.05). The end-diastolic volume increased after 2-psi inflation (P = 0.03). Cardiac output or stroke volume did not change. After standing, mean arterial pressure (P = 0.002), end-diastolic volume (P = 0.002), and stroke volume (P = 0.05) fell after suit deflation. Peripheral vascular resistance fell in the 2- and 4-psi inflation profiles. In the standing protocol, mean arterial pressure, end-diastolic volume, stroke volume, and cardiac output rose with all three inflation pressures (P less than 0.05). After reclining, heart rate increased (P = 0.02) and mean arterial pressure fell (P less than 0.05) in the 4- and 6-psi inflation profiles after suit deflation. Increases in mean arterial pressure are caused by increases in cardiac preload and cardiac output after inflation of the anti-G suit while subjects were standing. Increased cardiac preload was not consistently seen after inflation while subjects were supine. Changes in end-diastolic volume and mean arterial pressure were dependent on the pressure used to inflate the anti-G suit.

Adult↗

PubMedDate not supplied

Trichloroethylene, trichloroacetic acid, and dichloroacetic acid: do they affect fetal rat heart development?

Trichloroethylene (TCE), trichloroacetic acid (TCA), and dichloroacetic acid (DCA) are commonly found as groundwater contaminants in many regions of the United States. Cardiac birth defects in children have been associated with TCE, and laboratory studies with rodents report an increased incidence of fetal cardiac malformations resulting from maternal exposures to TCE, TCA, and DCA. The objective of this study was to orally treat pregnant CDR(CD) Sprague-Dawley rats with large bolus doses of either TCE (500 mg/kg), TCA (300 mg/kg), or DCA (300 mg/kg) once per day on days 6 through 15 of gestation to determine the effectiveness of these materials to induce cardiac defects in the fetus. All-trans retinoic acid (RA) dissolved in soybean oil was used as a positive control. Soybean oil is commonly used as a dosing vehicle for RA teratology studies and was also used in this study as a dosing vehicle for TCE. Water was used as the dosing vehicle for TCA and DCA. Fetal hearts were examined on gestation day (GD) 21 by an initial in situ, cardiovascular stereomicroscope examination, and then followed by a microscopic dissection and examination of the formalin-fixed heart. The doses selected for TCA and DCA resulted in a modest decrease in maternal weight gain during gestation (3% to 8%). The fetal weights on GD 21 in the TCA and DCA treatment groups were decreased 8% and 9%, respectively, compared to the water control group and 21% in the RA treatment group compared to soybean oil control group. The heart malformation incidence for fetuses from the TCE-, TCA-, and DCA-treated dams did not differ from control values on a per fetus or per litter basis. The rate of heart malformations, on a per fetus basis, ranged from 3% to 5% for TCE, TCA, and DCA treatment groups compared to 6.5% and 2.9% for soybean oil and water control groups. The RA treatment group was significantly higher with 33% of the fetuses displaying heart defects. For TCE, TCA, and DCA treatment groups 42% to 60% of the litters contained at least one fetus with a heart malformation, compared to 52% and 37% of the litters in the soybean oil and water control groups. For the RA treatment group, 11 of 12 litters contained at least one fetus with a heart malformation. Further research is needed to quantify the spontaneous rates of heart defects for vehicle control rats and to explain the disparity between findings in the present study and other reported findings on the fetal cardiac teratogenicity of TCE, TCA, and DCA.

Animals↗

PubMedDate not supplied

Trichloroethylene, trichloroacetic acid, and dichloroacetic acid: do they affect eye development in the Sprague-Dawley rat?

Maternal exposure to high doses of trichloroethylene (TCE) and its oxidative metabolites, trichloroacetic acid (TCA) and dichloroacetic acid (DCA), has been implicated in eye malformations in fetal rats, primarily micro-/anophthalmia. Subsequent to a cardiac teratology study of these compounds (Fisher et al. 2001, Int. J. Toxicol. 20:257-267), their potential to induce ocular malformations was examined in a subset of the same experimental animals. Pregnant, Sprague-Dawley Crl:CDR BR rats were orally treated on gestation days (GDs) 6 to 15 with bolus doses of either TCE (500 mg/kg/day), TCA (300 mg/kg/day), DCA (300 mg/kg/day), or all-trans retinoic acid (RA; 15 mg/kg/day). The heads of GD 21 fetuses were not only examined grossly for external malformations, but were sectioned using a modified Wilson's technique and subjected to computerized morphometry that allowed for the quantification of lens area, globe area, medial canthus distance, and interocular distance. Gross ocular malformations were essentially absent in all treatment groups except for the RA group in which 26% of fetuses exhibited micro-/anophthalmia. Using the litter as the experimental unit of analysis, lens area, globe area, and interocular distance were statistically significantly reduced in the DCA treatment group. Statistically significant reductions in lens and globe areas also occurred in the RA treatment group, all four ocular measures were reduced in the TCA treatment group but none significantly so, and TCE was without effect. Because DCA, TCA, and RA treatments were associated with significant reductions in fetal body weight (bw), data were also statistically analyzed after bw adjustment. Doing so dramatically altered the results of treatment group comparisons, but the severity of bw reduction and the degree of change in ocular measures did not always correlate. This suggests that bw reduction may not be an adequate explanation for all the changes observed in ocular measures. Thus, it is unclear whether DCA specifically disrupted ocular development even under these provocative exposure conditions. Clearly, however, if TCE is capable of disrupting ocular development in the Sprague-Dawley rat, a higher dose than that employed in the present study is required.

Administration, Oral↗