In vitro study of haemodynamics in a giant saccular aneurysm model: influence of flow dynamics in the parent vessel and effects of coil embolisation.

The purpose of this study was to investigate the influence of flow dynamics in the parent vessel and of intra-aneurysmal coil embolisation on flow pattern and pressure in an in vitro model of giant aneurysm. A pulsatile perfusion with a glycerol aqueous solution was installed in a silicone model of a lateral giant aneurysm. Flow visualization and pressure measurements were performed while modifying the flow rate, the pulsatility and the pulse rate in the parent vessel, and after partial coil embolisation. Vortices were formed during systole at the downstream lip of the aneurysm and circulated around the aneurysm. The centre and dome of the aneurysm were areas of fluid stagnation. Flow rate and pulsatility were the main factors which varied the pattern of flow within the aneurysm. Partial coil embolisation induced major flow disturbances in the aneurysm, in particular fluid stagnation at the dome. Pressure measurements were similar in the aneurysm and in the parent vessel. It was concluded that the pulsatility of flow is an important as the flow rate when considering the haemodynamics in a giant aneurysm. In the clinical context, this could explain the efficacy of vertebral artery occlusion in thrombosing giant vertebrobasilar aneurysms. Studies with intra-aneurysmal coil embolisation showed early fluid stagnation at the dome. This could result in embolic migration during endovascular treatment. Partial coil embolisation may prevent early rebleeding; however, it may induce additional mural stresses resulting from new haemodynamic forces and compliance mismatch.

[In vitro evaluation of Dibie-Musset vena caval filter]. / Evaluation in vitro du filtre cave Dibie-Musset.

The Dibie-Musset (DM) vena caval filter was evaluated on a hydraulic test bench reproducing flow conditions in the inferior vena cava: pressure, flow, viscosity, diameter and elasticity of the conduit. The results were compared with those obtained with the Greenfield filter (GF). In addition to classical measurements (captation and loss of load) we measured the velocity profile with a Doppler ultrasonic probe proximal and distal to the filter to study flow conditions before and after embolisation of clots. In order to circumvent the difficulties encountered with the use of real thrombi, chemical gels with visco-elastic properties, evaluated by viscosimetry, similar to those of blood clots, were used. Clots 45 mm long and 4 mm diameter were injected in several series of measurements. The DM filter was stable and did not migrate. In the horizontal position (flexible conduit) the DM filter was significantly more effective than the GF for less than 5 clots injected successively. The filtration capacity of both filters decreased with the number of clots captured. In the vertical position (rigid conduit), when there are less than 5 clots injected the two devices were perfectly effective. There was no significant difference between the two filters when 10 clots were injected. The loss of load resulting from the presence of the filter and clots was greater with the DM filter because of the greater captation capacity. However, the velocity profile distal to the filter was less disturbed with the DM filter because there was a more uniform distribution of the clots captured over the surface of the filter.(ABSTRACT TRUNCATED AT 250 WORDS)

Some effects of ochratoxin A, a mycotoxin contaminating feeds and food, on rat testis.

In previous toxicokinetic studies, ochratoxin A (OTA) was found in testicles of laboratory animals. Therefore its possible adverse effects on the rat testis have been investigated. Male Wistar rats 300 g +/- 20 g, randomised in groups of 5 animals, were given OTA: 289 micrograms/kg in 0.1 M NaHCO3 every 48 h for 2, 4, 6 and 8 weeks, by gastric intubation. This corresponds to a contamination of 2 ppm/day in the feeds. Controls were given only the vehicle. Some testicular enzymic activities and the stages of association of germinal cells (according to Leblond and Clermont) were determined. Some of these enzymic activities vary with the ochratoxin A poisoning in the homogenate of testicles: alpha-amylase, from 1905 +/- 145 units/g to 3190 +/- 128 units/g, alkaline phosphatase from 259 +/- 20 units/g to 323 +/- 15 units/g, gamma-glutamyltransferase (gamma GT), from 170 +/- 59 units/g to 900 +/- 65 units/g after 8 weeks. In adult rats, the increase of these enzymes, especially gamma GT, may be associated with an impairment of spermatogenesis and an accumulation of premeiotic germinal cells induced by OTA. Concerning the number of association stages of germinal cells, a decrease is observed for stages I and VII whereas stages XII and XIII increase after OTA treatment, indicating also a possible impairment of spermatogenesis. All these changes seem to be due to an earlier modification of the androgen status, the testosterone level in testes being 10.4 +/- 3.6 micrograms/g of protein after 3 weeks OTA treatment instead of 5.3 +/- 1 micrograms/g in control animals.

Saturnism caused by hand-made plates: partial diagnosis by a computer-aided program.

A man, aged 41 years, suffering from anaemia and abdominal pains was admitted to the Department of Medicine. Over the previous 2 years he had had several periods in hospital for these symptoms. There was, apparently, no occupational or accidental exposure to toxic substances and a correct diagnosis of the condition had not been possible. The computer-aided program AIDEDIAG II was therefore used to attempt a diagnosis. This approach indicated possible saturnism which was confirmed by metabolic and lead analyses. The lead source was identified as the hand-made food-plates used by the patient for his meals.

Human ochratoxicosis in France.

The prevalence of human ochratoxicosis in France is being determined using serum and plasma collected from apparently healthy people. The analytical method is based on the partition coefficient of ochratoxin A in aqueous and organic solvents, according to pH. High-performance liquid chromatography and spectrofluorimetry are used for detection and quantification (limit of detection, greater than 0.2 ng/ml). The presence of ochrotoxin A is confirmed by the action of carboxypeptidase to yield ochratoxin alpha or by derivatization of ochratoxin A with boron trifluoride. The significance of the interim values obtained and the number of positive samples is discussed. A comparison with the distribution of known values in Germany and Scandinavia could be helpful in risk assessment with a view to prevention.

A new geometric procedure for in vivo pulsed Doppler evaluation of velocity distribution inside the diametrical section of large arteries in humans.

A new geometric procedure determination of velocity profiles inside large human arteries, such as the brachial and femoral, has been developed. The procedure requires the use of two crystal element Doppler probes and a highly precise micromanipulator with three degrees of freedom. Precise positioning is needed to obtain the required high degree of parallelism between the vessel axis and the plane containing the two crystal elements. Once the appropriate degree of parallelism is achieved, a controlled translation of the probe, perpendicular to the ultrasonic beam plane, allows velocity waveforms to be recorded at sequential radial positions across the measured artery. Velocity profiles obtained with this geometric procedure depended on the type of artery investigated. The profiles measured with the geometric procedure were more symmetrical than those found using the electronic range-gated time system of reception. While the geometric and electronic methods were almost identical in determining the diameter values of the three arteries measured, the geometric procedure enabled greater accuracy for detailed analysis of velocity profiles in the peripheral large arteries in humans. Although the present methodology is not applicable in clinical practice due to prolonged data acquisition time (approximately 45 s) it is expected that future equipment improvements will reduce this time significantly.