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Biomedical subjects

J H Rankin

Publications and source records attributed to J H Rankin.

85 records · Page 5Linked to original sources
PubMed1975

Effect of surgical stress on the distribution of placental blood flows.

The distribution of the uterine and umbilical blood flows over the surface of the placenta was measured in 9 near-term sheep in an effort to assess the effects of surgical stress. The blood flows were observed to be relatively evenly distributed over the surface of the placenta. It was determined that the heterogeneity of distributions observed in the study could have caused the transplacental clearance of a very diffusible molecule to decrease by no more than 2 0/0. It is concluded that at the macroscopic level, in both the acute and chronic conditions, the uterine and umbilical blood flows of the near-term sheep are relatively evenly distributed over the surface of the placenta and that this distribution per se does not significantly contribute to transplacental concentration gradients.

Animals↗
PubMed1975

Uteroplacental blood flow during alkalosis in the sheep.

Uteroplacental blood flow was measured by the radioactive-microsphere technique in eight near-term pregnant ewes during a normal control period and during maternal metabolic alkalosis. All measurements were made on awake, unanesthetized animals. Alkalosis, defined for this study as an arterial pH of 7.60 or greater, was produced by the oral administration of sodium bicarbonate, 3 g/kg body wt. The rise in pH thus produced was unaccompanied by significant changes in systemic arterial blood pressure and cardiac output, while maternal arterial Pco2 rose slightly from control levels. Cotyledonary blood flow declined from a control value of 1,177 ml/min to 1,025 ml/min during alkalosis. This decline of 13 percent in cotyledonary blood flow is significant (P smaller than 0.002). Blood flow to the remaining uterine tissue, or noncotyledonary uterus, did not change with alkalosis, being maintained at approximately 195 ml/min. It is concluded that maternal alkalosis, unaccompained by major changes in Pco2 and systemic arterial pressure, causes a small increase in the resistance of the uteroplacental circulation.

Alkalosis↗
PubMed1975

Local regulation of the uterine blood flow by the umbilical circulation.

Observations were made of the responses of the uterine blood flow in the near-term pregnancy to occlusion of the umbilical circulation to a few cotyledons of the near-term sheep placenta and in one placenta of the multiparous rabbit pregnancy. It was found that the uterine blood flow declined to 67% of its predicted value 1 day after umbilical ligation in the sheep placenta and to 61% of its predicted value 1 day after the death of one of the fetuses of the rabbit pregnancy. The change in the uterine blood flow in response to the occlusion of the umbilical blood supply to the adjacent area is a local response and is similar in its time course and magnitude to the response of the whole placenta which has been previously observed by Raye et al. (9). This local response of the uterine blood flow is considered to be evidence that the uterine blood flow is in part determined and controlled by the structural or chemical nature of the adjacent fetal compartment.

Animals↗
PubMed1972

An evaluation of fetal renal function in a chronic sheep preparation.

Fetal renal function in the sheep was investigated in a chronic preparation which permitted repeated evaluations of urine flow and osmolality as well as renal clearances in animals which were unanesthetized and remote from acute surgical stress. Measurements of fetal blood pressure, pH, osmolality, fetal growth in utero, and final outcome did not indicate an adverse effect of the experimental procedure on the fetus. Fetal urine flow and osmolality were highly variable during the early postoperative period. They did not stabilize until 3-6 days after surgery, when urine osmolality became markedly hypotonic (range 65-160 mOsm/kg H(2)O) and urine flow rose to approximately 0.14 ml/min.kg. Fluctuations in urine flow and osmolality in the early postoperative period were the result of tubular reabsorption of water rather than a change in the glomerular filtration rate. The inulin-(14)C clearance, used as a measure of the glomerular filtration rate, was 1.05 +/-0.05 ml/min.kg (mean +/-sem) for all animals studied. Urea, fructose, sodium, and chloride were partially reabsorbed by the fetal kidney, while creatinine was secreted. Continuous drainage of fetal urine for 18 days in one animal demonstrated that the fetus was able to excrete large amounts of water, sodium, and fructose without apparent detrimental effects.

Animals↗
PubMedDate not supplied

The effects of surgical isolation and application of polypropylene spiral prostheses on tracheal blood flow.

Tracheal blood flow before and after division of the segmental tracheal blood supply with and without application of a polypropylene spiral prosthesis was measured in dogs by radiolabeled microsphere injection. Ischemia of the central part of the trachea, from the mid-cervical to mid-thoracic regions, was observed immediately after division of the segmental tracheal blood supply with and without polypropylene spiral prosthesis application. On day 3, tracheal blood flow was significantly decreased in the central part of the trachea with and without polypropylene spiral prosthesis application. On day 7, tracheal blood flow was significantly increased throughout the trachea, with no significant differences between animals with and without prosthesis application. There was no evidence of a collateral source of blood supply to the trachea. Surgical division of the segmental tracheal blood supply of the trachea. Surgical division of the segmental tracheal blood supply of the entire trachea is not recommended.

Animals↗
PubMedDate not supplied

Fetal heart rate and umbilical blood flow.

It has been suggested previously that norepinephrine does not change fetal placental vascular resistance but does change placental blood flow by changing fetal heart rate. We have tested the hypothesis that fetal heart rate is a determinant of fetal placental blood flow by observing changes in placental vascular resistance in 10 chronically catheterized near-term sheep fetuses. Pressures and flow were observed in the control condition and 150 s after the initiation of infusion of norepinephrine at 50 micrograms/min. The fetuses were then given 1.5 mg of atropine and control observations were again made. The norepinephrine infusion was repeated and pressures and blood flows were measured after 150 s. Atropine increased the fetal heart rate from 168 +/- 6 to 205 +/- 12 beats/min. Placental vascular resistance did not change. Norepinephrine resulted in bradycardia, hypertension and an increased placental vascular resistance. After pretreatment with atropine, norepinephrine resulted in tachycardia, hypertension and an increased placental vascular resistance. We conclude that fetal heart rate is not a major determinant of blood flow and that high doses of norepinephrine cause vasoconstriction of the placental vascular bed of the near-term sheep fetus.

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