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Biomedical subjects

P M Consigny

Publications and source records attributed to P M Consigny.

36 records · Page 2Linked to original sources
PubMed1989

Ultrasonic evaluation of erythrocyte aggregation dynamics.

The dynamics of aggregation and disaggregation of blood of varying hematocrit in oscillatory flow in a distensible horizontal tube was determined by measuring the developing echo intensity of the blood samples with a 10 MHz B-mode ultrasonic scanner. Early aggregation could be detected within 10 sec. of stoppage of flow. The rate of echo intensity buildup and thus, presumably the rate of aggregation when flow was stopped was inversely related to hematocrit, as was the rate of echo intensity reduction when flow was resumed. Polycythemic blood of 60% hematocrit showed no echo intensity increase over 5 min. Increasing the shear stress when flow was resumed resulted in rapid decreases in aggregation. In all cases, disaggregation following flow resumption was faster than aggregation following flow stoppage.

Adult↗
PubMed1988

Effects of angioplasty balloon inflation time on arterial contractions and mechanics.

The purpose of this study was to characterize and compare the immediate effects of short and long angioplasty inflation times on arterial contractions and passive mechanics and thereby determine if there is a potential advantage obtained by increasing the duration of balloon inflation. In each of 10 nonatherosclerotic New Zealand rabbits, one external iliac artery was dilated for 20 seconds, and the contralateral artery was dilated for 2 minutes. Although angioplasty stretched the arteries 27% and 30% for the short and long dilations respectively, the pre- and post-angioplasty arteriographic diameters were not different. Both short and long dilations had equal effects on passive biomechanics: circumferential wall stress was increased (P less than .01); wall thickness was decreased (P less than .01); the incremental elastic modulus was increased (P less than .01). In vitro studies of arterial rings demonstrated that maximal active contractile force in response to KCl (70 mM) was significantly (P less than .05) less for dilated arteries than for undilated arteries. More importantly, maximal active force after the 2-minute dilations was significantly (P less than .05) less than after the 20-second dilations. These results suggest that, when dilating normal arteries, increasing angioplasty balloon inflation time from 20 seconds to 2 minutes offers no mechanical advantage but produces more smooth muscle cell dysfunction, which may reduce vasospasm and restenosis after angioplasty.

Angioplasty, Balloon↗
PubMed1985

Clinical application of in vitro studies for barium-enema examination following colorectal biopsy.

A total of 150 colorectal biopsies were performed in 71 patients and correlated with the barium-enema examination (BE). The investigation was divided into two parts. In the first part, involving 19 patients, the depth of each biopsy specimen was determined histologically prior to BE and potential complications related to the biopsy-BE sequence were evaluated. In the second part, involving all 71 patients, the depth of biopsy specimens taken from various colon lesions was determined histologically without regard to the timing of BE. The results confirm previous in vitro findings in pigs and dogs, namely: (a) BE may be performed without delay following a superficial biopsy, but should not be performed until at least 6 days after a deep biopsy; (b) transcolonoscopic biopsies are likely to be superficial, while transproctoscopic biopsies have the potential to be deep; and (c) BE should be delayed at least 6 days following polypectomy or polyp biopsy performed with electrosurgery.

Barium Sulfate↗
PubMed1984

Comparison of superior vena cava and antecubital vein as DSA injection site.

A prospective study in 47 patients was undertaken to determine which of the two major sites for injection of contrast material, superior vena cava or antecubital vein, produces digital subtraction images of higher quality. Both injection sites were used to obtain images of the carotid and aortic arch areas in each patient. The two injection sites were also compared for ease of performance of the study, patient acceptance, and incidence of complications and motion artifacts. It was determined that the degree of vessel conspicuity is not affected by injection site when equal volumes of contrast material are injected. No significant differences in overall image quality attributable to injection site were found, except for carotid images obtained in the anteroposterior projection; for these images, the antecubital vein injection site produced significantly better images. Vessel conspicuity was not the major determinant of overall image quality as judged by radiologists.

Angiography↗
PubMed1983

Work in progress: transverse striations of the esophagus: association with gastroesophageal reflux.

Transverse mucosal ridging of the esophagus may be demonstrated on double-contrast esophagrams as transverse striations. A case review of 44 patients who had transverse striations was performed to evaluate the significance of the striations with respect to gastroesophageal reflux. Gastroesophageal reflux was significantly more common among patients who had transverse striations than it was in the general population who had been referred for the barium meal. This does not imply that all patients with transverse striations or with reflux at fluoroscopy have esophagitis. However, recognition of transverse striations should prompt careful evaluation for reflux and associated complications in symptomatic patients.

Adolescent↗
PubMed1982

Barium enema examination following biopsy of the rectum or colon.

A four-component study was designated to evaluate the possible risk of perforation during barium enema examination following biopsy of the rectum or colon. The study included a survey of gastrointestinal radiologists, an in vitro study of pig colons after biopsy, colon pressure measurements in human subjects, and histological analysis of human colonoscopic biopsy specimens. The results suggest that superficial biopsy of the rectum of colon performed with small colonoscopic forceps is a safe procedure and no waiting period is necessary before performing a barium enema study. However, biopsy of the colon or rectum with proctoscopic forceps appears to have greater potential for perforation and a waiting period between biopsy and barium enema study is recommended. Radiologists should distinguish between proctoscopic and colonoscopic biopsy procedures before determining when a barium enema study will be performed following biopsy.

Animals↗
PubMed1982

Acute and chronic microsphere loss from canine left ventricular myocardium.

We determined the effects of time, type of anesthesia, and myocardial infarction on loss of radioactive microspheres averaging 9 or 15 micrometers diameter from left ventricular myocardium. The principle used to compute losses was comparison of the number of microspheres injected directly into coronary arteries to the numbers remaining in myocardium, appearing within 2-4 min in the coronary sinus, or trapped in the lungs. Losses of 9-micrometers microspheres within 2 min of injection were significantly greater for halothane (mean 6.3%) than nitrous oxide anesthesia (mean 3.3%), and in the next 2 h increased to 11.7 and 7.9%, respectively. Over 5 wk in conscious dogs losses were as high as 40 and 11% for 9 and 15 micrometers microspheres, respectively. Losses were not greater for infarcted than normal muscle, and negligible radioactivity appeared in paracardiac lymph nodes. Microspheres leaving the heart were almost all below 10.3 micrometers diameter, so that microspheres with diameters 10-14 (mean 12) micrometers might be the best size to use for myocardial studies.

Anesthesia↗
PubMedDate not supplied

MR imaging of hepatic iron overload in rat.

To investigate the relationship of hepatic signal intensity and T2 with histologic grading in an animal model of oral iron overload and to determine the duration of feeding necessary to produce abnormalities detectable on magnetic resonance (MR) images, hepatic iron overload was induced in 12 rats by feeding them a diet supplemented with 4% carbonyl iron for 2-11 weeks. Iron overload seen on MR images was graded independently and blindly by two radiologists as normal, mild, moderate, or severe. The rats were killed, and histologic findings were graded blindly by four pathologists using a similar subjective scale. Hepatic T2 values were estimated from spin-echo images. In the rats with iron overload, intracellular iron deposition was noted on histologic studies. On MR images, hepatic signal intensity and T2 decreased after only 2 weeks of dietary iron overload, and both continued to decrease with longer duration of feeding. There was significant correlation between iron overload duration and changes on MR images and between MR images and histologic grading (r = .92, P = .0001 for both). The mean T2 of hepatic iron overload decreased with longer duration of feeding.

Animals↗
PubMedDate not supplied

Effects of laser thermal angioplasty on arterial contractions and mechanics.

In each of 8 rabbits, a fiberoptic with a 1.5 mm diameter metal tip was inserted into the abdominal aorta. After preheating with 8-10 watts of argon laser energy, the metal tip was passed through the external iliac artery. Thermal injury was evaluated by histology and by measuring arterial contractions and wall mechanics. The contralateral iliac artery was used as a control. Laser thermal angioplasty (LTA) produced foci of coagulation necrosis, medial thinning, and wall rupture. Concomitantly, maximal arterial contractile force was reduced by 80% (p less than 0.01) and arterial wall stiffness was decreased (p less than 0.05). These changes may have clinical implications with regard to the incidence and severity of vasospasm and restenosis following angioplasty.

Angiography↗
PubMedDate not supplied

Local delivery of an antiproliferative drug with use of hydrogel-coated angioplasty balloons.

PURPOSE: To determine the feasibility of using hydrogel-coated angioplasty balloons to deliver drugs that inhibit vascular smooth muscle cell (VSMC) proliferation. MATERIALS AND METHODS: In initial experiments, the tyrphostin RG-50872 (1 mumol/L) completely inhibited VSMC proliferation induced by platelet-derived growth factor (PDGF) in vitro when RG-50872 treatment preceeded PDGF exposure by 15 minutes. This inhibition was reversible and was not due to cell toxicity. In further experiments, hydrogel-coated and silicone-coated angioplasty balloons (2.5 mm in diameter by 20 mm in length) were coated with either 10 microL of RG-50872 (40 mmol/L in dimethyl sulfoxide [DMSO]) or DMSO vehicle, or were left uncoated. Afterward, each angioplasty balloon was inflated, submerged in 50 mL of culture media, and agitated for 2 minutes to promote drug release. Dilutions of this media were tested for their ability to inhibit VSMC proliferation. RESULTS: All hydrogel-coated balloons (n = 5) released sufficient RG-50872 to inhibit PDGF-induced VSMC proliferation by 95% or more, whereas none of the silicone-coated balloons (n = 4) did. DMSO-treated and untreated balloons had no effect on proliferation. CONCLUSION: These findings demonstrate that the hydrogel-coating on angioplasty balloons can take up and release sufficient RG-50872 to significantly inhibit smooth muscle cell proliferation. Further in vivo experiments are needed to determine if hydrogel-coated balloons can deliver sufficient RG-50872 to the arterial wall to affect VSMC proliferation.

Angioplasty, Balloon↗
PubMedDate not supplied

Drug delivery into the arterial wall: a time-course study with use of a lipophilic dye.

PURPOSE: One potential approach to the prevention of restenosis after angioplasty is to deliver antiproliferative agents directly to the angioplasty site. The purpose of this study was to determine the time course of drug penetration into the media of the balloon-dilated artery. MATERIALS AND METHODS: Balloon angioplasty of the left and right iliac arteries was performed once for 1 minute in each of five rabbits. A double-balloon catheter was then positioned at the site of angioplasty, and the fluorescent dye PKH26 (molecular weight, 961) was delivered under pressure to simulate drug delivery. Afterward, the arteries were removed and dye penetration into the media was measured on frozen cross sections by epifluorescence microscopy. RESULTS: Delivery of the dye was performed for periods ranging from 5 to 50 minutes at a mean pressure of 189 mm Hg. The depth of dye penetration (D, micrometers) was directly related to dye perfusion time (T, minutes) (D = 0.348T + 11.958, r = 0.496, P < .01). This equation predicts complete medial dye penetration in 81 minutes assuming an average intima-media thickness (40 microns). CONCLUSION: This study demonstrates that PKH26 can be delivered to the media of the dilated artery. However, the time required to obtain complete penetration may limit the utility of this double-balloon catheter approach to drug delivery.

Angioplasty, Balloon↗
PubMedDate not supplied

Placement of endothelial cells on the luminal surface of denuded arteries in vitro and in vivo.

PURPOSE: Experiments were performed to determine if the percutaneous placement of endothelial cells on denuded arterial surfaces is feasible. MATERIALS AND METHODS: For in vitro adhesion assays, rabbit microvascular endothelial cells were stained with a fluorescent marker and placed on the luminal surface of disks of denuded rabbit aorta. At varying times thereafter, the nonadherent cells were removed, and the adherent cells were quantitated with use of fluorescence microscopy. For in vivo studies, angioplasty was performed on external iliac arteries in five rabbits, and a double-balloon catheter, positioned at the dilatation site, was used to deliver fluorescent rabbit microvascular endothelial cells. Ten minutes (n = 2), 1 hour (n = 2), 1 day (n = 1), or 3 days (n = 1) after cell placement, the number of fluorescent cells remaining on each artery was determined. RESULTS: In vitro rabbit microvascular endothelial cell attachment was (a) serum-dependent, peaking with media containing 25% autologous serum; (b) time-dependent, peaking at 30 minutes; and (c) cell density-dependent. In vivo rabbit microvascular endothelial cell attachment was (a) noncircumferential, (b) appeared to be gravity-dependent, and (c) appeared unchanged over 3 days with respect to number of cells per cross-section and length of artery having endothelium. CONCLUSIONS: Percutaneous delivery of endothelial cells onto denuded arterial surfaces with use of optimal conditions is feasible and these cells remain adherent for at least 3 days.

Angioplasty, Balloon↗
PubMedDate not supplied

1998 SCVIR Gary J. Becker Young Investigator Award. Endovascular repair of arterial pseudoaneurysms with use of a perfusion balloon catheter.

PURPOSE: Pseudoaneurysms represent contained disruption of the arterial wall. Iatrogenic pseudoaneurysms frequently complicate complex endovascular procedures. With use of an animal model, the authors attempted to determine the safety and efficacy of using a perfusion balloon catheter (PBC) to thrombose surgically created pseudoaneurysms. MATERIALS AND METHODS: An in vitro system measured maximum flow volume through a 5-F PBC. Pseudoaneurysms were created in domestic swine with use of a jugular vein patch anastomosed to a femoral arteriotomy. The PBC was inflated across the pseudoaneurysm neck for 30-minute intervals until thrombosis was confirmed by ultrasound. Completion arteriography was performed to evaluate for vascular complications. RESULTS: Maximum flow through the PBC was 62.6 mL/min measured at a constant pressure gradient of 120 mm Hg. Five pseudoaneurysms were created in four animals. The PBC completely thrombosed all five lesions. The mean treatment duration was 129 minutes (+/- 39 minutes SD). No native arterial injury, in situ thrombus, or distal embolization occurred. Partial recanalization of three of the five treated pseudoaneurysms was identified on follow-up arteriography and gross sectioning (n = 2 and n = 1, respectively). CONCLUSION: The PBC safely and effectively thrombosed surgically created pseudoaneurysms. Partial recanalization of treated pseudoaneurysms was demonstrated. Clinical trials are warranted.

Aneurysm, False↗
PubMedDate not supplied

Resistance of freshly adherent endothelial cells to detachment by shear stress is matrix and time dependent.

PURPOSE: The placement of endothelial cells on the surfaces of arteries immediately after vascular interventions has the potential to limit restenosis by inhibiting intimal thickening and by stimulating arterial enlargement. Because such re-endothelialization is dependent on rapid formation of strong endothelial cell-matrix interactions, experiments were performed to identify the extracellular matrix that provided endothelial cells with the greatest resistance to detachment by a shear stress in the least amount of time. MATERIALS AND METHODS: Rabbit microvascular endothelial cells were plated onto glass slides coated with collagen, laminin, vitronectin, or fibronectin. After allowing 5-45 minutes for cell adhesion, each slide was placed in a parallel plate chamber, and the number of cells present before and after exposure of the cells to shear stresses (1-25 dynes/cm2) were counted. RESULTS: Endothelial cell retention to the matrix-coated slides was time and matrix dependent. The percentages of endothelial cells retained after adhesion times of 5, 15, 30, and 45 minutes followed by exposure to 15 dynes/cm2 were 9%, 20%, 32%*, and 38%* for collagen; 7%, 20%, 36%*, and 49%* for laminin; 35%, 47%, 62%, and 76%* for vitronectin; and 64%, 58%, 71%, and 78% for fibronectin, respectively (*P < .05 versus 5 minutes adhesion). Similar results were obtained for lower and higher shear stresses, indicating that cell retention was independent of shear stress above 1 dyne/cm2. CONCLUSIONS: The resistance of freshly adherent endothelial cells to detachment by shear stress is matrix- (fibronectin approximately equal to vitronectin > laminin approximately equal to COL) and time-dependent. Fibronectin provided the greatest cell retention in the least amount of time.

Animals↗
PubMedDate not supplied

Immediate and long-term effects of angioplasty-balloon dilation on normal rabbit iliac artery.

The present study was performed to determine the immediate (hours) and long-term (28-day) effects of angioplasty-balloon dilatation on arterial wall diameter, histology, response to vasoconstrictors, and passive mechanics. Dilated left iliac arteries of New Zealand rabbits were compared to control, right iliac arteries. In the immediate studies, dilation increased arteriographic diameter by 32%, denuded the endothelium, stretched and may have lysed smooth muscle cells, decreased arterial wall thickness, and increased passive stress and incremental elastic modulus. The dilated arteries failed to contract to norepinephrine or potassium chloride. In contrast, 28 days after dilation, arteriographic diameter had returned to normal, an intimal thickening had formed, passive stress and the incremental elastic modulus had decreased to below normal, and the arteries contracted, but to only 53% to 67% of control. Angioplasty had no long-term effect on arterial sensitivity (EC50) to potassium chloride or serotonin but did produce a decreased sensitivity (6X) to norepinephrine. These studies demonstrate that the effects of dilatation of the normal artery are partially reversible, suggest that restenosis after angioplasty is more likely to be due to intimal proliferation than increased arterial stiffness, and suggest that vasospasm of arteries after long-term recovery from the dilation is more likely to be mediated by serotonin than by norepinephrine.

Angioplasty, Balloon↗