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Biomedical subjects

D L Reid

Publications and source records attributed to D L Reid.

32 records · Page 2Linked to original sources
PubMed1989

Effects of atrial natriuretic factor on maternal ovine vascular resistance.

Atrial natriuretic factor (ANF) is a potent endogenous vaso-dilator and diuretic peptide of uncertain physiologic relevance. In this study, the effects of ANF on normal and angiotensin II constricted placental, uterine and renal vessels were examined in pregnant sheep. Ewes were equipped with catheters to monitor vascular pressures, infuse drugs and measure blood flow by the microsphere technique. An electromagnetic flow sensor was placed around the middle uterine artery and electromyogram electrodes were attached to the uterus. ANF was administered into a branch of the uterine artery to minimize its systemic effects. The experiment included two protocols. First, blood flows and pressures were measured after a 5-min period of saline infusion into the uterine artery. These measurements were repeated at the end of a 5-min infusion of ANF (6.25 micrograms.min-1) into the uterine artery. During the second protocol, angiotensin II (AII) was infused via the jugular vein at 5 micrograms.min-1 for 10 min and ANF (6.25 micrograms.min-1) was infused through the uterine artery during the second half of the AII infusion. In the absence of AII, ANF lowered blood pressure from 97 +/- 6 to 90 +/- 6 mmHg (P less than 0.05); and placental resistance from 67.8 +/- 11.3 to 57.3 +/- 10.4 mmHg.min.ml-1 per g (P less than 0.01). Uterine resistance did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1989

The effect of acute hypoxaemia on ventricular function during beta-adrenergic and cholinergic blockade in the fetal sheep.

The effect of acute hypoxaemia on right and left ventricular function was investigated in 8 fetal sheep (137-140 days gestation). Fetuses were instrumented with electromagnetic flow sensors on the ascending aorta and the main pulmonary artery. After 8 days recovery, hypoxaemia was achieved by reducing the maternal ewe's inspired O2 concentration to 13.1 +/- 1.5%. Control and hypoxaemic arterial blood values were pH 7.37 +/- 0.04 (SD) and 7.35 +/- 0.06, PCO2 48.0 +/- 2.8 and 47.6 +/- 5.1 mmHg, PO2 19.9 +/- 2.2 and 11.4 +/- 1.5 mmHg, haematocrit 37.5 +/- 1.2 and 39.5 +/- 2.2, respectively. Arterial pressure increased insignificantly with acute hypoxaemia (50.2 +/- 3.9 to 53.6 +/- 8.1 mmHg). Left and right ventricular performance was assessed by generating biventricular function curves relating stroke volume to mean atrial pressure. All function curves were composed of steep ascending and plateau limbs that intersected at a breakpoint. Comparing control and hypoxaemia function curves, the left ventricular stroke volume breakpoints were 0.79 +/- 0.20 and 0.78 +/- 0.21 ml/kg, respectively, while the right ventricular stroke volume breakpoints were 0.99 +/- 0.11 and 0.88 +/- 0.21 ml/kg (n.s.). In 4 fetuses, acute hypoxaemia was associated with significant increases in arterial blood pressure (P less than 0.05). In these fetuses, the right ventricular function curve was shifted significantly downward compared to the control right ventricular curve. When nitroprusside was given to these hypertensive fetuses to return blood pressure to control levels, the right ventricular function curve returned to baseline. We conclude that even under conditions of extreme hypoxaemia, ventricular function is well preserved in the normotensive fetal sheep. However, when increases in arterial pressure also accompany hypoxaemia, detectable changes in right ventricular function can be accounted for by changes in arterial pressure.

Animals↗
PubMed1989

Ovine fetal coronary and cerebral vascular responses to forskolin.

The time related hemodynamic responses to forskolin-elicited increases in cAMP were studied in the near-term fetus. Catheters and electrodes were inserted into 6 fetal sheep to measure arterial, venous and thoracic pressures, electrocorticogram, and electrocardiogram. At gestational day 134, experiments were performed to determine the effect of forskolin infusion (400 micrograms/ml at 1.03 ml/min for 5 min) on fetal blood pressure, coronary and cerebral blood flow and resistance. Blood flow measurements were made using 15 microns microspheres labelled with radioactive isotopes during the control period and at 0, 5, 10, 15, and 45 min after forskolin infusion. Forskolin infusion was always initiated during a high-voltage electrocortical epoch and was given twice in each animal. In each case, forskolin caused electrocortical activity to change from high-voltage state to an intermediate voltage state. Blood pressure fell significantly by the end of the infusion period and returned to control levels 10 min later. Fetal heart rate and coronary blood flow were immediately elevated by forskolin (P less than 0.01) whereas cerebral blood flow did not increase until 5 min later (P less than 0.01). Cerebral blood flow was still elevated (P less than 0.05) 45 min after the end of forskolin infusion, whereas coronary blood flow had returned to control levels. Both cerebral and coronary vascular resistance fell significantly in response to forskolin infusion (P less than 0.01). This effect lasted at least 15 min and had returned to control levels 45 min after forskolin had been terminated.

Animals↗
PubMed1989

Effects of antipyrine on electrocortical state and regional blood flows in the mature sheep fetus.

Antipyrine has recently been shown to decrease prostaglandin production in mature fetuses. Prostaglandins are important in the regulation of blood flow, and electrocortical state has been shown to influence regional blood flows. To assess the effect of antipyrine on blood flow, it is important to take electrocortical state into account. We therefore examined the effect of antipyrine infusion on placental, renal, and cerebral blood flow during periods of high and low voltage electrocortical activity. Six mature sheep fetuses were equipped with electrodes for determination of electrocortical state. Intravascular catheters were inserted into the fetal forelimb and hindlimb arteries and vein and an additional catheter was placed in the maternal femoral artery. After a five day recovery period, pressures were recorded and electrocorticogram was monitored for 3 full cycles of electrocortical activity. Antipyrine infusion (30 mg.min-1) was then started. After 1 h, blood flow measurements were made by microsphere method in the first 5 min of each subsequent electrocortical state for the next three full cycles. Blood flows are expressed as ml.min-1 per g (mean +/- SEM). Cerebral blood flow was 1.587 +/- 0.272 during low and 1.209 +/- 0.171 during high voltage periods (P less than 0.05). Placental blood flow was 2.103 +/- 0.294 during low and 2.047 +/- 0.325 during high voltage electrocortical activity. Renal blood flow was 2.394 +/- 0.330 during low and 2.360 +/- 0.386 during high voltage periods of electrocortical activity. Blood pressure was 50.8 +/- 1.8 mmHg during low and 52.8 +/- 2.3 mmHg during periods of high voltage activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Matching of maternal and fetal flow ratios in the sheep placenta.

Local interaction of maternal and fetal placental blood flows was studied in two groups of unanaesthetized near-term sheep. Five sheep were exposed to a simulated dive to 100 feet of seawater (4.03 atmospheres) for 25 min. Six fetuses received an infusion of noradrenaline (6.8 micrograms/[kg x min]). Radioactive microspheres were administered simultaneously to mother and fetus before (control) and after (test) the experimental manipulation. Maternal and fetal relative activities, defined as % of total placental radioactivity divided by % of total placental weight, were calculated for 1-g pieces of cotyledonary tissue under control and test conditions. Pieces of cotyledons were defined as matched if the direction of change in relative activity from control to test was the same for mother and fetus. In the absence of an interaction between the maternal and fetal placental circulations, the probability of a piece of cotyledon being matched is 0.5. In each series of experiments the proportion of all cotyledon pieces having maternal and fetal relative activities that changed in the same direction was significantly greater than 0.5. Thus, the majority of the placental mass responds to a physical or chemical perturbation of the fetus in such a way that changes in relative perfusion are qualitatively matched in the adjacent maternal and fetal placental circulations.

Animals↗
PubMed1988

Dose-response curves of the uterine and placental vascular beds to prostaglandin I2.

Local infusion of prostaglandin I2 (PGI2) has been reported to dilate the uteroplacental vasculature in a dose-dependent manner. In this experiment we attempted to distinguish the placental and nonplacental (uterine) components of this response over four concentrations of PGI2. Eleven near-term sheep were chronically instrumented for determination of regional blood flows by the use of radioactive microspheres. PGI2 was administered in a retrograde manner via a branch of the middle uterine artery at 1, 3, 10, and 20 micrograms/min. Flows were measured before (control) and after 5-minute infusions at each of the four concentrations (test). The uterine vasculature vasodilated in response to local PGI2 infusion. The 10 micrograms/min dose, for example, produced a mean (+/- SEM) flow of 0.70 +/- 0.07 ml/min/gm; the control value was 0.41 +/- 0.03 ml/min/gm (p less than 0.001). At 20 micrograms/min the test and control flows were 0.75 +/- 0.16 and 0.36 +/- 0.06 ml/min/gm (p less than 0.05), respectively. Uterine vascular resistance fell in a dose-dependent manner as well. There was no evidence of placental vasodilation at any of the doses tested. Renal vasodilation and decreased systemic arterial pressure at higher PGI2 doses suggest a recirculation effect. We conclude that PGI2 does not dilate the placental vasculature over the dose range of 1 to 20 micrograms/min and that the reported vasodilation of the uteroplacental vasculature is a result of decreased resistance in the uterine vasculature alone.

Animals↗
PubMed1988

Effects of forskolin on placental vascular resistance in rabbits.

Forskolin is a direct stimulant of adenylate cyclase and increases cAMP production. It also acts as a vasodilator. To study the effect of forskolin infusion on rabbit maternal vascular resistance, we instrumented 11 pregnant rabbits with catheters in the left ventricle, jugular vein, and left and right femoral arteries. After a 2-day recovery period, one of two protocols was performed. In the control period of the first protocol (N = 6), 50% ethanol in saline was infused at 0.103 ml.min-1 for 5-min. Forskolin (10(-3) M) in 50% ethanol was then infused for 5 min at 0.103 ml.min-1. After each infusion period, regional blood flows were measured by microsphere injection. Data are expressed as means +/- SEM. Blood pressure decreased from 81 +/- 3 to 79 +/- 3 mm Hg, (P less than 0.05, N = 10) during forskolin infusion. Total placental resistance fell from 180.3 +/- 10.7 to 133.8 +/- 12.0 mm Hg.min.ml-1 per gram, P less than 0.05. Cerebral, coronary, and renal vascular resistance fell significantly. During the second protocol (N = 5), angiotensin II (0.05 microgram.min-1) was infused for 5 min followed by the addition of forskolin (10(-3) M at 0.103 ml.min-1) to the infusate. Regional blood flows, vascular resistances and blood pressures were determined. Blood pressure fell from 99 +/- 6 to 92 +/- 7 mm Hg (P less than 0.05) when forskolin was added to the infusate. Placental resistance fell from 202.5 +/- 21.6 to 158.0 +/- 29.0 mm Hg.min.ml-1 per gram (P less than 0.05). While cerebral vascular resistance did not change, renal and coronary resistances fell in response to forskolin. This study demonstrates that forskolin is able to dilate rabbit placental vessels alone and in the presence of the vasoconstrictive agent angiotensin II.

Angiotensin II↗
PubMed1987

Fetal lamb ventricles respond differently to filling and arterial pressures and to in utero ventilation.

Right and left ventricular function were investigated in 12 fetal lambs (127-140 days gestation) instrumented with electromagnetic flow sensors on the ascending aorta and the main pulmonary artery, and with vascular catheters. Nine fetuses were equipped with a postductal aortic occluder and the trachea was cannulated in eight. Control arterial blood values were pH 7.36 +/- 0.02 (SD), PCO2 49.3 +/- 2.3 torr, PO2 18.4 +/- 1.7 torr, and hematocrit 37.3 +/- 4.4%. Biventricular function curves relating stroke volume to mean right and left atrial pressure were generated by rapid withdrawal and reinfusion of fetal blood. Both function curves were composed of steep ascending and plateau limbs that intersected at a breakpoint. Stroke volumes at the breakpoints were 0.94 +/- 0.19 ml.kg-1 and 0.63 +/- 0.15 ml.kg-1 for right and left ventricle, respectively (p less than 0.001). During postductal aortic occlusion, arterial pressure increased by 19.3 +/- 7.9 torr while right ventricular stroke volume decreased by approximately 48% and left ventricular stroke volume decreased by approximately 9%. In utero ventilation increased arterial pressure, heart rate, PO2, and oxygen content. Right atrial pressure increased from 3.9 +/- 1.3 to 5.8 +/- 2.9 torr (p less than 0.05); left atrial pressure from 3.5 +/- 1.5 to 10.0 +/- 4.4 torr (p less than 0.05). Aortic flow nearly doubled (112 +/- 29 to 211 +/- 35 ml.min-1.kg-1) (p less than 0.05), and the left ventricular function curve shifted upward. The right ventricular function curve was shifted downward during ventilation. We conclude that the fetal ventricles differ significantly in their outputs, response to changes in arterial pressure, and to the onset of in utero ventilation.

Animals↗
PubMed1986

Androgen receptors in brain and pituitary of female rats: cyclic changes and comparisons with the male.

The in vitro binding of a synthetic androgen, methyltrienolone ([3H]-R1881), to brain and pituitary (PIT) cytosol and nuclear extracts was determined in male and female rats. Purified cytosol was prepared from PIT or hypothalamic-preoptic area-amygdala (HPA) and incubated in the presence of 0.1 to 10 nM [3H]-R1881. Scatchard analysis revealed the presence of a single, saturable, high-affinity binding site in PIT cytosol with a dissociation constant (Kd) of 0.42 X 10(-10) M in females and 0.95 X 10(-10) M in intact males. The Kd of HPA cytosol was much less in castrated males [0.47 +/- 0.05 (SEM) X 10(-10)M, n = 7] and females (0.63 +/- 0.1 X 10(-10) M, n = 4) than in intact males (5.8 +/- 1.1 X 10(-10) M, n = 8). Treatment of castrated males with dihydrotestosterone (DHT) for 24 h (250 micrograms/100 g of body weight) increased the Kd of HPA cytosol only slightly (1.6 X 10(-10) M, mean of two replicates). Scatchard analysis of salt-extracted nuclear androgen receptor (ARn) showed a single, high-affinity binding site with similar Kd values in PIT and HPA of intact and castrated, DHT-treated male rats (PIT Kd = 7.3 X 10(-10) M, 9.3 X 10(-10) M; HPA Kd = 1.5 X 10(-9) M, 1.3 X 10(-9) M, respectively). Competition studies involving a range of several radioinert steroids revealed that the binding of [3H]-R1881 to cytosol (ARc) and nuclear extract was specific for androgen receptor when triamcinolone acetonide (10 microM) was added. The ARc and ARn levels were quantified in PIT, preoptic area (POA), hypothalamus (HT), amygdala, hippocampus, and cortex by single point estimation. Significantly (p less than 0.01) greater amounts of ARc were detected in PIT of ovariectomized females (32.7 +/- 2.9 fmol/mg of protein) than in that of orchidectomized males (22.33 +/- 1.6 fmol/mg of protein). The highest levels in the brain were seen in HT and POA. Pituitary ARc in females varied throughout the estrous cycle. Significantly (p less than 0.01) greater amounts were detected on estrus (45.8 +/- 2.2 fmol/mg of protein) and proestrus (39.0 +/- 1.9 fmol/mg of protein) than on diestrus (29.2 +/- 1.5 fmol/mg of protein). These data confirm the existence of specific receptors for androgen in male and female brain and PIT, and suggest an important role for androgen in the control of PIT hormone secretion in the female.

Animals↗
PubMedDate not supplied

In vivo placental permeability to hydrophilic solutes as a function of fetal weight in the guinea pig.

The permeability of the placenta was measured with unlabelled inulin in unanaesthetized guinea pigs. Inulin was injected into the sows and the plasma concentrations were recorded at regular intervals. The inulin contents of the conceptuses were calculated from fetal weights, fetal plasma inulin concentrations and a measured inulin distribution volume of 180 ml/kg fetus. From fetal inulin contents and the time integral of the difference in maternal and fetal plasma concentrations, we calculated a mean inulin permeability of 29 +/- 9 (s.e.m.) nl/s per gram placental weight. The inulin permeability per gram placental weight rose statistically significantly with increasing fetal weight. Comparison with a similar rise observed for the smaller cyanocobalamin molecule studied previously led to the conclusions that in the last ten days of gestation the transplacental passages narrow while at the same time there are apparent changes in the numbers and/or lengths of these passages that suffice to increase the unrestricted permeability fourfold.

Animals↗
PubMedDate not supplied

Kansas nursing occupational projection 1995-2005.

The Kansas State Department of Human Resources recently released a study of occupational employment throughout the state. The data was compiled using staffing pattern employment from the 1992, 1993 and 1994 occupational employment statistics program survey of industries, along with base year 1993 average annual employment for Kansas industries. Projected demand for occupational employment is significantly affected by the projected employment for industries.

Employment↗