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Biomedical subjects

D F Anderson

Publications and source records attributed to D F Anderson.

At least 19 recordsLinked to original sources
PubMed1992

Plasma renin activity responses to graded decreases in renal perfusion pressure in fetal and newborn lambs.

We examined the relationship between acute reductions in renal perfusion pressure, as approximated by femoral arterial blood pressure, and plasma renin activity in the uninephrectomized fetal lamb. Renal perfusion pressure was reduced and maintained at a constant value by controlled partial occlusion of the aorta above the renal artery. After 15 min of reduced blood pressure, blood samples were taken for determination of plasma renin activity. This protocol was performed 22 times in 11 fetal lambs. Additionally, three of the fetuses were delivered by cesarean section and studied as newborns for the first week of life. In the fetus, there was a linear relationship between log plasma renin activity and femoral arterial blood pressure (P less than 0.01). After birth, the relationship still existed, although it was shifted to the right (P less than 0.0001). We conclude that there is a significant relationship between plasma renin activity and renal perfusion pressure in the fetal lamb, and as early as 1 day after birth, this relationship shifts to the right in the newborn lamb.

Analysis of Variance↗
PubMed1991

Short-term saralasin blockade of renal hypertension in fetal lambs.

1. In the fetal lamb, suprarenal aortic blood flow reduction is known to lead to an upper body hypertension. The dependency of this hypertension on the renin-angiotensin system was investigated. 2. Intravenous infusions of saralasin or saline vehicle were begun before suprarenal aortic blood flow reduction and continued for 24 h. 3. In those fetuses receiving saline, upper body arterial blood pressure was significantly elevated both 60 min (P < 0.05) and 24 h (P < 0.05) after blood flow reduction. In those fetuses receiving an infusion of saralasin, upper body arterial blood pressure failed to rise after 60 min of blood flow reduction. However, 24 h later, blood pressure was elevated (P < 0.05), though the increase was not as great as that seen in the saline infused fetuses (P < 0.05). 4. From these results, we conclude that the initial increase in upper body arterial blood pressure seen after suprarenal aortic blood flow reduction is dependent upon the renin-angiotensin system. However, as early as 1 day later, some other mechanism is responsible for sustaining the hypertension.

Animals↗
PubMed1991

Failure of acute saralasin to reverse chronic hypertension in fetal lambs.

Upper body arterial hypertension developed in 12 fetal lambs after chronic suprarenal aortic blood flow reduction. Sixty minutes after blood flow reduction, intravenous saralasin infusion was able to reduce upper body mean arterial blood pressure to control levels. Although saralasin infusion was able to decrease upper body arterial blood pressure after 1 day of hypertension, it was not able to return blood pressure to control levels. Three or more days later, saralasin was unable to cause a significant reduction in upper body arterial blood pressure. We conclude that, although the renin-angiotensin system has a role in maintaining the elevated blood pressure after greater than or equal to 1 day of suprarenal aortic blood flow reduction, some other mechanism also participates. We have ruled out a role for changing blood volume, and our results suggest that an elevation of plasma catecholamines is not responsible. Some other pathway for fluid regulation available to the fetus may be responsible.

Angiotensin II↗
PubMed1990

Disproportionate referrals for child academic/behavior problems: replication and extension.

Drabman, Tarnowski, and Kelly (1987) investigated children's month of birth in relation to mental health referrals and found that the younger children in a class were disproportionately referred for services. We conducted a replication and extension of the Drabman et al. investigation. Data were collected on children's (N = 222) cognitive and academic competencies. Results indicated that (a) younger children in a class were disproportionately referred, (b) the referral pattern remained constant across all grades examined, (c) the referral pattern could not be explained by differences in children's competencies, and (d) although the youngest children in the class were referred most frequently, they had the lowest rate of qualification for special services.

Achievement↗
PubMed1990

Filtration of water from mother to conceptus via paths independent of fetal placental circulation in sheep.

1. Four pregnant ewes were operated on at 121-126 days of gestation. An electromagnetic flow sensor and an inflatable occluder were placed on the maternal common internal iliac artery. The ovarian arteries and veins were ligated. Indwelling catheters were placed in a maternal femoral artery and uterine vein and in the amniotic and allantoic fluids. An inflatable occluder was placed around the umbilical cord, close to the fetal abdomen. 2. Eight to nine days after surgery, the cord was occluded, the fetus killed and uterine blood flow reduced to one-quarter of its control value. The rate of water loss from the uterine circulation was calculated from blood flow and the venoarterial difference in blood osmolality. The amniotic and allantoic fluids were made hypertonic by infusion of 2 l into each sac of a solution of 1.5 mol of mannitol per litre of saline. The rate of water loss from the maternal uterine circulation was then measured five times over the next 4.5 h. 3. The combined filtration coefficient surface area product of the interfaces between maternal blood and the amniotic and allantoic sacs, normalized per kilogram fetal body weight, was (2.8 +/- 0.5) x 10(-6) cm3 s-1 kPa-1 kg-1 (mean +/- S.E.M).

Allantois↗
PubMed1990

Model study of placental water transfer and causes of fetal water disease in sheep.

The purpose of the computer simulation was to use experimentally measured parameters of placental water transfer to compute conceptual water acquisition during the last third of ovine pregnancy and to evaluate the possible role of each of these parameters in the pathophysiology of polyhydramnios. Total conceptual water at birth was almost insensitive to the value of the placental filtration coefficient. It was more sensitive to fetal and maternal placental blood flows, the concentrations of actively transported or metabolically produced solutes in fetal plasma (bicarbonate, fructose, alpha-amino acids, urea, lactate), and the hydrostatic pressure difference across the placental barrier. It was quite sensitive to the NaCl reflection coefficient and permeability. We conclude that the actively transported or produced solutes in fetal plasma constitute a primary driving force. The opposing diffusion gradient of NaCl, and to a much lesser extent that of glucose, are essential to restrain the process. The causes of polyhydramnios in this species are, in order of probability, an increase in the placental diffusion permeability of NaCl, a decrease in the placental reflection coefficient for NaCl, or an increase in the concentration of an osmotically effective solute in fetal plasma, by active transport or metabolic production.

Animals↗
PubMed1989

Animal model for polyhydramnios.

Chronic intravenous infusion of angiotensin 1 [182 micrograms/(kg.day)] into fetal lambs caused gross polyhydramnios. Infusions of comparable volumes of vehicle or lower concentrations of angiotensin 1 [48 micrograms/(kg.day)] did not cause gross polyhydramnios.

Angiotensin I↗
PubMed1989

Suprarenal aortic flow reduction versus angiotensin I infusion in fetal sheep.

In the unanaesthetized fetal sheep, long-term suprarenal aortic blood flow reduction will cause upper body arterial blood pressure to increase. To see if the response to this procedure was entirely due to the concomitant increase in plasma renin activity, we gave an angiotensin I infusion of several days to 7 fetal sheep and compared their responses to those of 4 fetal sheep undergoing partial occlusion of the aorta above the renal arteries. Both protocols caused upper body arterial blood pressure to increase to comparable levels. Angiotensin I infusion had no effect upon venous blood pressure while suprarenal aortic blood flow reduction caused a significant increase in venous blood pressure as early as 1 day after blood flow reduction. Haematocrits were unchanged in the fetuses with flow restriction but increased in the infused fetuses. We conclude that long-term angiotensin I infusion in the fetus does not mimic the entire complex of responses to suprarenal aortic blood flow reduction.

Angiotensin I↗
PubMed1988

Extraplacental transfer of water in the sheep.

1. Ten pregnant ewes were operated on at 130 days of gestation. The fetal trachea was intubated with a double-lumen tube, an inflatable occluder was placed around the umbilical cord, vascular catheters were placed in the fetal carotid artery and jugular vein and in the maternal jugular vein, and multiple catheters were placed in the amniotic and allantoic sacs. 2. At 139 days gestation, the fetus was ventilated in utero, and the umbilical cord was occluded. The extrafetal fluids were circulated by means of roller pumps. Known activities of radio-iodinated human serum albumin, tritium-labelled water and 14C-labelled urea were injected into the amniotic and/or allantoic fluids. Samples were obtained at 30 min intervals for several hours. 3. Extrafetal fluid volumes were calculated from the albumin distribution volumes. The amounts of labelled water transferred to the maternal circulation were calculated from the changes in tracer concentrations in extrafetal fluids and fetal plasma. 4. No labelled albumin was detected in fetal or maternal plasma. The permeability-surface area product of labelled water at the combined amniotic and allantoic interfaces with the ewe was 28.2 +/- 2.8 ml/min (mean +/- S.E.M.). In five preparations the values could be separately calculated for amniotic and allantoic interfaces. The two mean values (19 +/- 4 and 12 +/- 1 ml/min) were not significantly different from each other. The permeability-surface area product at the combined interfaces with the fetus was 0.96 +/- 0.17 ml/min. Urea was so much less permeable than water that no reliable permeability-surface area products could be calculated in all of the preparations. 5. We calculated that the hydraulic conductivity of the combined extraplacental pathway is more than 0.5% of that of the placenta. Because the osmotic gradient across the extraplacental pathway is one to two orders of magnitude greater than that across the placenta, extraplacental transfer of water can significantly affect intrauterine water volume.

Animals↗
PubMed1987

Arterial pressure after chronic reductions in suprarenal aortic flow in fetal lambs.

Experiments were performed on 13 fetal lambs of 126 days gestational age. Seven days after surgery, suprarenal aortic blood flow was reduced to 70% of control with an inflatable occluder for a period of at least 4 days. This produced an almost constant aortic pressure difference of 35 mmHg across the occluder. Plasma renin activity (PRA) rose in the next hour from 6 to 42 ng.ml-1.h-1 (P less than 0.01) but decreased to a level that was statistically insignificantly above normal by the next day. PRA as a function of lower body arterial blood pressure showed rapid adaptation. Upper body arterial blood pressure was statistically significantly elevated by 5 mmHg within 5 min and continued to rise while plasma renin activity was falling. Femoral artery blood pressure dropped immediately but returned to near normal within 1 h and remained there. The long-term upper body hypertension was irreversible with a 30-min infusion of saralasin. Subrenal aortic flow reduction caused none of these changes. We conclude that the fetal kidneys can regulate arterial blood pressure upward but that the long-term effect does not depend solely on a direct vasoconstrictive action of angiotensin.

Animals↗
PubMed1986

Eating disordered behaviors: a comparison of male and female university students.

This study compared male and female students on measures characteristic of eating disordered behavior. Measures investigated were subscales of the Eating Disorders Inventory and of the Restrained Eating Scale. Results indicated that both males and females reported a fundamental pattern of eating disordered behavior. This pattern consisted of going on and off diets with an accompanying complaint of a lack of confidence in recognizing and identifying sensations of hunger and satiety. Females differed from males in that they reported more anorexic behavior and scored significantly higher on most measures of eating disordered behavior. Although the fundamental pattern of disordered eating leading to bulimia may be similar between the sexes, females appear to be at greater risk to the development of these behaviors.

Body Image↗
PubMed1986

Fetal O2 consumption in sheep during controlled long-term reductions in umbilical blood flow.

Electromagnetic flow sensors and inflatable occluders were placed on the distal aortas of nine fetal lambs of 111-124 days gestation; indwelling vascular catheters were placed in a lower body artery and vein and the common umbilical vein. After a control period of 7.6 +/- 2.1 (SD) days, distal aortic flow was reduced to about 60% of control flow; placental flow fractions of distal aortic flow were 77 +/- 5%, control; 69 +/- 11% during flow reduction. Duration of the flow reductions was 9.6 +/- 6.5 days. Fetal O2 consumption fell from 6.4 +/- 1.5 to 5.3 +/- 1.1 ml X min-1 X kg-1 (P less than 0.02) as umbilical blood flow was reduced from 202 +/- 47 to 116 +/- 36 ml X min-1 X kg-1 (P less than 0.001). Least-squares polynomial regression analysis showed that O2 consumption was a linear function of umbilical blood flow (P less than 0.01). With regard to long-term fetal O2 consumption, there was no evidence for a margin of safety in fetal umbilical blood flow.

Animals↗
PubMed1985

Flow through the foramen ovale of the fetal and new-born lamb.

Right and left atrial pressures were measured in eight chronically instrumented fetal and neonatal lambs. Flows were measured with a combination of electromagnetic flow sensor and microsphere techniques. Three of the fetuses were ventilated in utero during the measurements. Four fetuses were studied as neonates immediately after spontaneous term delivery and one was studied as a normal fetus in utero. Data from these preparations were augmented with seven sets of previously reported data from normal fetuses in utero for analysis. Linear least-squares regression analysis demonstrated that inferior caval vein flow into the right atrium was inversely related to right atrial pressure. This flow could not be demonstrated to depend on the velocity of blood in the inferior caval vein. Non-linear least-squares regression analysis of foramen ovale flow as a function of a power of the flow in the inferior caval vein revealed that the square of the velocity of blood in the inferior caval vein predicted foramen ovale flow. Of the two forces that determine foramen ovale flow in the fetus, pressure difference and kinetic energy, the latter was far larger than the former. These results support the theory that the fetal foramen ovale is maintained in an open position by the kinetic energy of the blood in the inferior caval vein.

Animals↗
PubMed1985

Alteration of arterial gas composition by positive pressure ventilation in the unanesthetized fetal lamb in utero.

To study the effectiveness of in utero ventilation in altering fetal arterial gas composition, we ventilated 15 near-term fetal lambs with a range of inspired gas mixtures. To accomplish this, double lumen nasogastric tubes were surgically placed in the tracheas of 15 near-term (135 days' gestation) fetal lambs. After 4 +/- 1 SD postoperative days, the fetuses were respired by positive pressure ventilation. 13 of these fetuses were also ventilated with their umbilical cords completely occluded. Ventilation was maintained for an average of 4.5 h (range 2.5-7.5 h). All 15 fetuses were effectively oxygenated on room air when exposed to a small net positive end expiratory pressure. In fetuses with intact umbilical cords, PaO2 could be maintained at levels between 11 and 280 mm Hg and PaCO2 from 36 to 139 mm Hg by altering the inspired O2 and CO2 with a gas mixing device. During umbilical cord occlusion, PaO2 was regulated from 2.2 to 103 mm Hg and PaCO2 from 37 to 187 mm Hg.

Animals↗
PubMed1984

Regulation of fetal placental blood flow in the lamb.

Inflatable occluders were placed on the distal aorta of 11 fetal lambs. After 1 wk of control measurements, fetal placental blood flow was reduced to about two-thirds of its control value for an average period of 2 wk. No allowance was made for fetal growth. During the period of flow restriction, fetal growth was 2%/day. Femoral arterial blood pressure was reduced from a control value of 41 to 27 mmHg (P less than 0.001). There was an insignificant increase in carotid arterial blood pressure from 48 to 50 mmHg. Placental resistance to flow did not decrease more than could be accounted for by the increase in gestational age in the course of the experiment. It is concluded that fetal placental blood flow is not under feedback control, since neither of the determinants of flow (i.e., driving pressure and resistance) responded to its chronic reduction.

Animals↗
PubMed1982

Water flux due to colloid osmotic pressures across the haemochorial placenta of the guinea-pig.

1. Experiments were performed on pregnant guinea-pigs with gestations of about 44 days to term (65 days). Under anaesthesia, one fetus in each litter was given a volume equal to 1.31% of estimated body weight (v/w) of a 40% solution of 60k-90k dextran in Ringer solution by I.P. injection. One control litter-mate received the same amount of Ringer solution, but without dextran. Other litter-mates served as non-injected controls. 2. At 20.4 (+/- 4.7 S.D.) hr later, the sow was re-anaesthetized and all fetuses were removed and weighed. They were then dried to constant weight. Wet weights and dry weights were corrected for the weights of the injected materials. 3. Wet weights were normalized by dry weights to account for differences in body size. The average normalized wet weight of the fetuses injected with the dextran solution was 10.9% greater than that of the injected controls and 16.0% greater than that of the non-injected controls. 4. The results were not affected by the removal of all amniotic fluid at the time of the injections. 5. The results could not have been due to non-colloid osmotic forces. The Ringer solution was slightly hypo-osmotic compared to guinea-pig plasma and the dextran contained negligible amounts of non-colloids. 6. The applied colloid osmotic pressure of less than 20 torr caused the transfer of a physiologically significant volume of water in a period of 1 day.

Animals↗
PubMed1982

Effects of age and temporal placement of a modeled skill on children's performance on a balance task.

The present investigation explored the effect of age and temporal placement of a modelled skill on performance on a balance task. 60 boys, aged 7 and 9 yr., were randomly assigned to one of three conditions. The model was presented before any trials were attempted, midway, or not at all during 12 trials. A 2 (age) X 3 (model condition) X 12 (trials) repeated-measures design was utilized. Analysis of variance indicated significant effects of age, temporal appearance of the model, and an interaction of model by age for time on-balance. Model affected younger subjects but not older ones. Treatment did not affect off-balance errors. Findings for age and temporal placement are not consistent with some previous research.

Child↗