Down-regulation of myometrial atrial natriuretic factor receptors by progesterone and pregnancy and up-regulation by oestrogen in rats.

We previously reported that pregnancy and progesterone treatment abolish and ovariectomy reduces the tocolytic activity of atrial natriuretic factor (ANF) on rat uterus. The present study was carried out to determine whether the hormonal state of the animal influences myometrial ANF receptors. A single high-affinity binding site for 125I-labelled ANF(1-28) was detected in myometrial membrane preparations partially purified by discontinuous sucrose gradient centrifugation.

Inhibition of the tocolytic activity of atrial natriuretic factor by progesterone and potentiation by progesterone receptor antagonist RU486 in rats.

1. The influence of progesterone on the activity of atrial natriuretic factor (ANF) on rat myometrial motor activity was determined in vitro. 2.

Ontogeny of responses of rabbit aorta to atrial natriuretic factor and isoproterenol.

Ontogeny of the vasorelaxant effects of atrial natriuretic factor (ANF) and isoprenaline and of the vasoconstrictor effects of potassium and phenylephrine were studied on aortic strips from rabbits aged 1, 2, 3, 6, 10 and 32-48 (adult) weeks. ANF caused complete relaxation of phenylephrine- and potassium-contracted aortic strips from all age groups of rabbits and its potency was not altered by age and by the agent used to cause contractions. On the other hand, the vasorelaxant efficacy and potency of isoproterenol decreased with age.

Refractoriness of the gravid rat uterus to tocolytic and biochemical effects of atrial natriuretic peptide.

1. Effects of atrial natriuretic peptide (ANP) on tension development, particulate guanylate cyclase activity and guanosine 3':5'-cyclic monophosphate (cyclic GMP) concentrations of uteri from oestrogen-treated, progesterone-treated, ovariectomized and pregnant rats were determined in vitro. 2.

Comparison of computerized tomography with magnetic resonance imaging (MRI) in the evaluation of encephalic ventricular volume.

The volume of the encephalic ventricles was determined from computerized tomographic (CT) and magnetic resonance imaging (MRI) scans of seven subjects without apparent pathology and three subjects with enlarged ventricles. Since there are many conditions in which the encephalic ventricles become enlarged such as Alzheimer's disease and hydrocephalus, accurate measurement of these structures provides (1) a valuable and safe means of aiding in the diagnosis of such conditions and (2) important follow-up information on affected patients. This paper presents the data obtained from the second phase of a three phase study.

Evaluation of encephalic ventricular volume from the magnetic resonance imaging scans of thirty-eight human subjects.

Accurate volume determination of the encephalic ventricles is of importance in several clinical conditions, including Alzheimer's presenile dementia, schizophrenia, and benign intracranial hypertension. Previous studies have investigated the accuracy with which magnetic resonance imaging (MRI) can be used in clinical practice to evaluate the encephalic ventricles. However, adequate evaluation of pathological conditions depends on a sufficient amount of morphometric data from normal subjects.

Bronchodilator activity of atrial natriuretic peptide in guinea pigs.

Atrial natriuretic peptide (ANP) produced concentration-dependent relaxation of isolated guinea pig tracheal chains contracted with histamine, serotonin, carbachol, and arachidonic acid. ANP was a full agonist. ANP was two- to three-fold less potent when compared with isoprenaline in relaxing histamine-, serotonin-, and arachidonic acid-contracted tracheal chains.

Optimal fitting of computer model simulations to first transit cardiac radionuclide curves--II.

A discrete-time, lumped-parameter mathematical model of the human cardiopulmonary circulation as it appears during a first-transit radionuclide study has been described. An optimal fitting process is used to match curves obtained from the model to curves obtained from first transit studies in order to estimate the parameters of the subject's heart. The development of the optimization technique is described in this paper.

Computer model for simulation of first transit cardiac radionuclide curves--I.

A discrete-time, lumped-parameter mathematical model of the human cardiopulmonary circulation as it appears during a first-transit radionuclide study is developed. Eleven compartments, four delays, and 26 transfer paths are modeled, including the entire circulation from an input compartment before the vena cava to an output compartment after the aorta. The 26 transfer paths include forward and reverse flow through the heart valves, backflow from the atria into the veins, and five types of shunts.

Selective increase in placental blood flow by atrial natriuretic peptide in hypertensive rats.

Effects of atrial natriuretic peptide on systemic, renal, uterine, and placental hemodynamics were determined in 16-day pregnant normotensive and hypertensive rats and in 20-day pregnant normotensive rats under pentobarbital anesthesia. Relative to 16-day pregnant normotensive rats, the total peripheral resistance was higher in 16-day pregnant hypertensive and 20-day pregnant normotensive rats; atrial natriuretic peptide significantly (p less than 0.05) decreased the total peripheral resistance in the latter two groups of animals.

Peptide YY (PYY) stimulates intrinsic enteric motor neurones in the rat small intestine.

The effects of peptide YY (PYY) on motor activity of the rat small intestine, were studied using isolated organ bath preparations arranged for recording muscle activity in the longitudinal axis. PYY induced TTX sensitive concentration-dependent contractions and/or relaxations of the longitudinal muscle in different regions of the small intestine. In the duodenum PYY evoked only "cholinergic" contractions (3 x 10(-8)-3 x 10(-7) M).

Captopril renography in two kidney and one kidney Goldblatt hypertension in dogs.

In order to improve on the technique of noninvasive detection of renal artery stenosis, we studied the effects of angiotensin converting enzyme inhibition with captopril on individual kidney hemodynamics and function as assessed by technetium-99m diethylenetriaminepentaacetic acid [( 99mTc]DTPA) renal flow studies and iodine-131 orthoiodohippurate [( 131I]hippuran) renography in experimental Goldblatt's hypertension. In two-kidney, one-clip (renin-dependent) hypertension, captopril (1.5 mg/kg bolus with 1.

Effect of captopril on 99mTc-diethylenetriaminepentaacetic acid renograms in two-kidney, one clip hypertension.

In an effort to improve on the noninvasive detection of renal artery stenosis, we investigated the effect of angiotensin converting enzyme inhibition on computer-assisted 99mTc-diethylenetriaminepentaacetic acid (DTPA) renal flow studies in a canine model of two-kidney, one clip hypertension and compared these findings with clearances of inulin and p-aminohippuric acid in the stenotic and contralateral kidney before and after converting enzyme inhibition. The 99mTc-DTPA renal flow study with the converting enzyme inhibitor captopril (1.5 mg/kg bolus with 1.

Improved computer-assisted nuclear imaging in renovascular hypertension.

Computer-assisted dynamic renal studies using both the 90 second 99mTc-DTPA and the conventional 30 minute 131I-Hippuran methods were performed in nine patients with angiographically proven renal artery stenosis. Time activity curves for both studies were derived from regions of interest selected from the computer-acquired dynamic images. The following parameters were used to assess renal blood flow: differential maximum activity, minimum/maximum activity ratio, and peak width.

Technetium-99m DTPA renal flow studies in Goldblatt hypertension.

Computer-assisted dynamic renal studies were performed on a group of 14 mongrel dogs before and after the induction of unilateral renal artery stenosis. Ninety-second technetium-99m diethylenetriaminepentaacetic acid ( [99mTc]DTPA), 15-min [99mTc]DTPA, and 30-min iodine-131 orthoiodohippurate ( [131I]hippuran) time-activity curves were analyzed and correlated with reduction of renal blood flow as measured by electromagnetic flow probe and PAH clearance techniques. Parameters of the 90-sec [99mTc]DTPA curves found to be significantly different for the same kidney before and after stenosis were: upslope, curve width at 75% maximum, maximum activity value, and differential (stenotic/contralateral) maximum activity ratio.