Search PubMed⌕ Search

Biomedical subjects

C G Caro

Publications and source records attributed to C G Caro.

At least 37 records · Page 2Linked to original sources
PubMed1990

Effects of isosorbide dinitrate on the pattern of arterial blood flow in healthy human subjects.

1. Blood velocity measurements have been made in the superficial femoral artery, 10 cm downstream of the common femoral artery bifurcation, in healthy human subjects, using a multi-channel Doppler ultrasound device. 2. In a randomized double-blind protocol, the effects of isosorbide dinitrate were examined during a 2 h period. 3. The changes induced by isosorbide dinitrate include: (i) an increase in the width of the artery and a reduction in brachial arterial blood pressure, implying relaxation of arterial smooth muscle; (ii) an increase in reverse flow and a decrease in time-averaged mean velocity associated with a relatively small decrease of the velocity excursion during the cardiac cycle, implying an increase in flow pulsatility; and (iii) an alteration of the flow pattern both in the core and near the vessel walls.

Adult↗
PubMed1988

The effect of varying albumin concentration of the hydraulic conductivity of the rabbit common carotid artery.

Rabbit common carotid arteries were cannulated in situ, after ligation of their branches, and transferred to a perfusion apparatus in such a way that they were maintained at their physiological dimensions and the endothelium remained intact. The vessels were pressurized to 150 cm H2O with Krebs solution and the wall smooth muscle was relaxed with 10(-4) M NaNO2. The rate of inflow of perfusate into the vessels was measured by following the movement of a bubble in a calibrated capillary which, when steady, was taken to indicate the transmural filtration rate. The filtration rate was 1.48 +/- 0.26 X 10(-6) cm sec-1 (11) (mean, SD, n) with 1 g/dl bovine serum albumin in Krebs solution. The values with 0, 4, 7, and 10 g/dl, normalized by the 1 g/dl value were 1.38 +/- 0.16 (7), 0.80 +/- 0.05 (9), 0.65 +/- 0.03 (8), and 0.47 +/- 0.06 (9), respectively. The hydraulic conductivity of the wall was also found to depend on perfusate albumin concentration. The 1 g/dl value was 0.92 +/- 0.17 X 10(-8) cm sec-1 (cm H2O)-1 (11) and the values with 0, 4, 7 and 10 g/dl normalized by the 1 g/dl value were 1.35 +/- 0.16 (7), 0.87 +/- 0.06 (9), 0.81 +/- 0.03 (8), and 0.72 +/- 0.06 (9), respectively. The findings were analyzed in relation to models involving interaction of albumin with the endothelial glycocalyx, concentration polarization at the blood/wall interface, dependence of flux on solvent viscosity and dependence of the porosity of the wall interstitium on solvent flux. Both concentration polarization and variation of the porosity of the wall interstitium provide reasonable quantitative explanations for the findings.

Albumins↗
PubMed1987

Effect of cigarette smoking on the pattern of arterial blood flow: possible insight into mechanisms underlying the development of arteriosclerosis.

By means of non-invasive multichannel doppler ultrasound measurements, cigarette smoking in healthy subjects was shown to increase arterial wall stiffness and to alter the pattern of arterial blood flow, decreasing the pulsatility index. The pattern of blood flow seems to be a contributory factor in the development of arteriosclerosis, and these findings may provide insight into the underlying mechanisms.

Adult↗
PubMed1984

Factors influencing arterial wall mass transport.

Arterial wall mass transport has particularly attracted attention because it may be implicated in the development of arterial disease, including arteriosclerosis. A short review is presented of the structure of the arterial wall and of studies of mass transport within it. Recent findings confirm that mass transport occurs across the entire arterial wall apparently from the lumen to the adventitial lymphatics. Evidence has emerged of inhomogeneity of the distribution volume for extracellular tracers in different layers of the wall. An attempt is made to interpret results which indicate that distension per se of arteries and increase of medial smooth muscle tone tend to compact the medial interstitium whereas pressure driven convection across the wall tends to expand that tissue. These findings imply a potentially important role of endothelial permeability, smooth muscle tone and luminal pressure in influencing solute transport in the wall and wall transport properties.

Animals↗
PubMed1983

Effect of noradrenaline, sodium nitrite and isosorbide dinitrate on albumin transport in the wall of the excised rabbit common carotid artery.

The effects of noradrenaline (NA), sodium nitrite (NaNO2) and isosorbide dinitrate (ISDN) on the steady state distribution of 125I-labelled albumin in the wall of excised rabbit common carotid arteries were studied. The vessels were incubated in Tyrodes solution either at relaxed length and zero transmural pressure (non-pressurized) or at in vivo length and a transmural pressure of 70 mm Hg (pressurized). Label was applied in the same concentration at both the luminal and outer surfaces. The mean medial uptake in pressurized vessels was greater after treatment with 10(-7) M NA than after additional treatment with either 10(-3) M NaNO2 or 10(-3) M ISDN. The opposite was found for non-pressurized vessels. The medial uptake by NA-treated pressurized vessels was greater than that by NA-treated non-pressurized vessels, while the reverse was found for NaNO2- or ISDN-treated vessels. We conclude that the different patterns of uptake seen in these vessels results from the relative effects of externally applied stress (elongation and pressurization), smooth muscle tone and convection through the wall, on the properties of the interstitium, and possibly from the effects of the vasoactive agents on endothelial permeability.

Albumins↗
PubMed1983

Effect of vasoactive agents and applied stress on the albumin space of excised rabbit carotid arteries.

Experiments were undertaken on excised rabbit common carotid arteries to assess whether the distribution volume for radioactively labelled albumin is influenced by smooth muscle tone or externally applied stress. In arteries at relaxed length and zero transmural pressure, the distribution volume in the media was reduced by noradrenaline at concentrations exceeding 10(-9) M and increased by both sodium nitrite and isosorbide dinitrate at concentrations exceeding 10(-4) M. The distribution volume was lower in both the media and adventitia of segments at in vivo length pressurized with air to prevent convection through the wall, than in segments at relaxed length and zero transmural pressure. Noradrenaline decreased and sodium nitrite increased the medial distribution volume of the tracer in these air-pressurized segments. The vasoactive agents did not change the [51Cr]EDTA space in vessels at relaxed length and zero transmural pressure, although there were small alterations of medial water content. Transient conditions raise interpretative difficulties because of uncertainty about endothelial permeability and time-dependent changes of wall properties. The changes of the distribution volume for labelled albumin are thought to reflect changes in the properties of the interstitium.

Albumins↗
PubMed1983

The mass transport of the arterial wall: effect of mechanical stresses and vasoactive agents, including nitrates.

Arteriosclerosis is a slowly progressing disease. It is important, therefore, to seek means of delaying its progress both in pre-symptomatic patients and in patients with circulatory disorders. Various features of the disease, among them the focal distribution of the lesions, imply that changes in blood composition cannot alone account for its occurrence and that a contribution must come from the arterial wall, possibly from its mass transport properties. We review recent findings concerning arterial wall mass transport. Movement of material occurs right across the arterial wall from the lumen to the adventitial lymph and it appears that the media may act as a barrier to the efflux of material from the wall. Work currently in progress suggests that among factors which influence arterial wall mass transport are the level of arterial blood pressure, endothelial permeability and the tone of the medial smooth muscle. Further fundamental study is needed but consideration would now seem justified as to whether the progression of arteriosclerosis might be influenced by pharmacological agents which affect the wall mass transport.

Albumins↗
PubMed1982

Structural response of the rabbit thoracic aorta and inferior vena cava to in situ collapse.

When the transmural pressure of the rabbit aorta falls below 5 mmHg in situ, the vessel collapses to form regions of high curvature along both lateral margins which stain deeply with Trypan Blue dye. The ultrastructure of the collapsed vessel was examined in order to investigate its response to localized stresses. Lamellar convolution was characterized by a convolution index, C.I. (length of a segment of lamella divided by the length of the arc of best fit spanned). In high curvature regions, C.I.'s of the internal and outer lamellae were 1.64 SD 0.20 and 1.04 SD 0.04 respectively. Corresponding values in low curvature regions were 1.30 SD 0.08 and 1.31 SD 0.04. The mean wave numbers of internal lamellar convolutions in high and low curvature regions were 53 mm-1 and 63 mm-1 SD 7 mm-1. When the ratio of medial thickness to internal radius, t/ri exceeded 1.9, the internal lamella buckled and endothelial cells detached. The mode of cell deformation depended on the position of the cell junctions relative to the convolutions. A small series of studies showed the endothelial cells in the vena cava did not detach for t/ri less than 15.0.

Animals↗
PubMed1980

Net albumin transport across the wall of the rabbit common carotid artery perfused in situ.

We have studied the transport of radioactively labelled albumin in the rabbit common carotid artery perfused in situ at 100 cm H2O luminal pressure in the anaesthetized living animal, assessing the distribution of concentration across the wall by means of sequential frozen sectioning. We have compared the findings with those of experiments in which we have attempted to saturate the wall with label. Our findings support the belief that there is a net transport of macromolecules across the arterial wall. They show in addition that the wall is inhomogeneous. The distribution volume for label is greater in the adventitia than the media, which appears to offer a larger resistance. The transport process is seemingly dominantly diffusional.

Animals↗
PubMed1977

Effect of positive external pressure on calf volume and local venous haemodynamics.

The pressure external to the calf was increased suddenly in 11 normal subjects and the resulting change in calf volume (considered to be mainly a change of calf vein blood volume) was followed using a mercury-in-rubber strain gauge. For a small increase of pressure the volume decreased exponentially and increased linearly when the pressure was suddenly released. A simple theory was developed which treats the calf veins as a single volume with a single compliance and a single outflow resistance. Using the theory, the following average results were obtained from measured values: effective venous compliance 1-1%kPa (SD 0.3); effective venous outflow resistance 3.8 s kPa/% (SD 1-3); and total flow into the veins from themicrocirculation 0.054%/s (SD 0.020) (% refers to a change in volume expressed as a percentage of the initial volume of the calf). The significance of the findings is considered with special reference to the occurrence of calf vein thrombosis.

Adult↗
PubMed1975

Uptake of 125I albumin by the endothelial surface of the isolated dog common carotid artery: effect of certain physical factors and metabolic inhibitors.

A study has been made, under transient conditions, of the uptake of 125I albumin by the endothelial surface of isolated dog carotid arteries. Effective rate constants were determined and the apparent activation energy was calculated to be about 13 kcal/mol in the range 25-37 degrees C. Label uptake was not significantly altered by the presence of 1 mmol/1 potassium cyanide or 10 mmol/1 iodoacetate in the incubating medium, or by the absence of substrate from it, consistent with the process being primarily passive. It appeared that the label entered the wall mainly by other routes than the endothelial inter-cell clefts.

Animals↗