Biomedical subjects

B Ayres

Publications and source records attributed to B Ayres.

10 recordsLinked to original sources

PubMed1997

Transcripts for functionally distinct isoforms of chicken GATA-5 are differentially expressed from alternative first exons.

Our analysis of cDNA and genomic clones unexpectedly revealed that the chicken gata-5 gene is differentially expressed from alternative first exons. Moreover, we show that the respective transcripts are differentially processed to yield mRNAs for two distinct isoforms of GATA-5. The major isoform, which we described previously, has two CXNCX17CNXC zinc fingers typical of a vertebrate GATA factor. The minor isoform, on the other hand, has only one such zinc finger. We show that this novel isoform localizes within the nuclei of transfected cells and can bind to a consensus GATA site. This truncated isoform of GATA-5 is compromised in its ability to transactivate a simple target gene, however, and thus is functionally distinct from the major isoform of GATA-5.

Amino Acid Sequence↗

PubMed1997

Danger of false intubation after traumatic tracheal transection.

Blunt tracheobronchial injuries may be difficult to diagnosis at presentation but can pose major airway difficulties. We present a patient with a tracheal transection who underwent intubation with the tip of the endotracheal tube exiting the trachea and terminating in the mediastinum adjacent to the distal trachea. He underwent surgical repair of the injury with end-to-end anastomosis. Although intubation over a flexible fiberoptic bronchoscope is desirable in cases of suspected tracheobronchial injury, it may not be feasible. In cases of suspected tracheobronchial injuries with blind endotracheal intubation, the possibility of false intubation should always be entertained.

Adult↗

PubMed1996

Comparison of the deployment and healing of thin-walled expanded PTFE stented grafts and covered stents.

This study evaluated the deployment and short-term healing of thin-walled expanded polytetrafluoroethylene (ePTFE) stented grafts and covered stents as endoluminal prostheses in normal canine aortas and in an abdominal aortic aneurysm (AAA) model. Stented grafts consisted of a 7 cm length of 3 mm internal diameter ePTFE graft (Impra, Inc., Tempe, Ariz.) with two P-188 Palmaz stents (Johnson & Johnson Interventional Systems, Warren, N.J.) deployed along the inner surface of the ends of the graft to secure the prosthesis to the arterial wall. Covered stents were fabricated by placing a 3.7 cm length of 3 mm internal diameter thin-walled ePTFE graft over a P-394 Palmaz stent. Four covered stents and four stented graft prostheses (two of each prototype in the normal canine aorta and AAA model) were implanted in eight animals. One prosthesis of each type in each model was removed at 30 days and one at 60 days. Prior to removal, prostheses were evaluated by CT scan, arteriography, and intravascular ultrasound imaging with values compared to those obtained when the prostheses were deployed. Gross inspection and microscopic evaluation were performed at scheduled explantation. In general, the stented grafts were more difficult to accurately deploy. Healing and maintenance of long-term patency without significant luminal obstruction or occlusion occurred in only one 30-day sample in a normal canine aorta. The 30-day stented graft specimen that had been implanted in an AAA and required the addition of a covered stent to seal a maldeployment of the distal segment was also patent. The 60-day stented graft in the normal canine aorta was occluded with narrowing of the graft between the stents. The 60-day stented graft in the AAA was patent with one central fold and thrombus occupying approximately 20% to 30% of the lumen at this site. In contrast, the covered stent devices were less difficult to accurately deploy. All of the covered stent devices were patent with well-incorporated surfaces. Deployment of covered stents was more accurate and less complicated compared to stented grafts. All patent endoluminal prostheses and stent surfaces were well incorporated into aortic tissues. Problems with graft narrowing, folding, and subsequent thrombosis occurred in the unstented segments of the stented grafts. These preliminary findings support the further development and use of completely supported (stented) devices as endoluminal prostheses.

Angioplasty, Balloon↗

PubMed1996

Evaluation of a modular endovascular bifurcation prosthesis in a canine aortic aneurysm model.

PURPOSE: The study evaluated the deployment and healing of a novel self-expanding modular bifurcation endovascular prosthesis in a canine abdominal aortic aneurysm model. The endoluminal prosthesis consists of self-expanding nitinol stents lined by a synthetic prosthesis. One component of the device is a bifurcated body with a 12- to 14-mm diameter aortic segment and an integral 7- to 8-mm diameter iliac limb. The bifurcated body also has a stent-reinforced opening (pant-leg) for subsequent insertion of a contralateral 7- to 8-mm diameter iliac limb component. METHODS: Seventeen bifurcated prosthesis were placed; 7 were inserted through the left common carotid artery and 10 from the femoral arteries. With either route of access the 16F or 17F aortoiliac limb and the 13F iliac limb delivery catheters enabled easy passage and secure positioning of the bifurcated prostheses. Predeployment and postdeployment inspection of the dimensions and continuity of the aortoiliac prosthetic components were evaluated by cinefluoroscopy and intravascular ultrasonography (IVUS). RESULTS: After deployment was done, interval patency was assessed with angiography, IVUS, and contrast-enhanced computed tomography with the prostheses removed for analysis at 1 week (n = 4), 1 month (n = 3), 3 months (n = 4), and 6 months (n = 6). Five of the first seven implanted prostheses had occlusion of segments of the device. In two dogs the bifurcated body and both legs were occluded. In the other three the nonoccluded leg and bifurcation body were fully patent. In the first seven animals IVUS at implantation showed compression of an iliac leg by the orifice of the contralateral iliac component. After concentric fixation of the flow divider was performed, only one additional iliac limb occlusion occurred in the next 10 animals. Cinefluoroscopy, computed tomography, IVUS imaging, and histologic analysis of retrieved specimens demonstrated healing of the aortoiliac prostheses without evidence of perigraft leaks. CONCLUSIONS: This feasibility study demonstrates the ability to deploy and maintain acceptable patency of a self-expanding endoluminal, modular bifurcation prosthesis in a canine aortic model. Clinical evaluation of the device is planned for the near future.

Alloys↗

PubMed1996

Preliminary clinical outcome and imaging criterion for endovascular prosthesis development in high-risk patients who have aortoiliac and traumatic arterial lesions.

PURPOSE: This report reviews our preliminary experience of prospective treatment of arterial lesions with endoluminal grafts in a Food and Drug Administration (FDA)-approved, investigator-sponsored Investigation Device Exemptions study. The utility and accuracy of various imaging methods, including angiography, cinefluoroscopy, computed tomography (CT), intravascular ultrasonography (IVUS), and duplex scanning, in performing the procedures was also assessed. METHODS: Thirty-one patients were evaluated; 17 patients were treated, including 11 with abdominal aortic aneurysms, one with an aortic occlusive lesion, two with iliac artery aneurysms, and three with traumatic arteriovenous fistulas. Twelve of the 14 patients who had aorta and iliac artery lesions were high-risk. The mean follow-up of patients treated was 9 months (range, 6 to 15 months). RESULTS: Aortoaortic endoluminal interposition procedures were not successful for treating abdominal aortic aneurysms early in the study (n = 3). Aortoiliac endoluminal bypass, contralateral iliac artery occlusion, and femorofemoral bypass procedures were successful in seven of eight subsequent cases (88%), with no incidence of endoleaks at either the proximal or distal fixation sites using the deployment methods described in this report. The 30-day operative mortality rate on follow-up evaluations for patients who underwent aortoiliac procedures was 14% (two of 14). Other major complications included transient renal failure in three patients that required short-term (two to eight times) dialysis, one arterial perforation and one dissection, and one prolonged intubation. No myocardial infarctions or strokes occurred. After major complications or identification of limitations in the study, the protocol was modified with the approval of the FDA to help avoid the recurrence of the same problems. There were no deaths or complications in the trauma cases. CONCLUSIONS: Contrast-enhanced CT (axial images and spiral reconstructions) was the most accurate method to determine candidacy for aortoiliac procedures and to choose the site for deployment of the devices. Angiographic scans were misleading in several patients regarding the critical determinants of patient candidacy and device deployment, particularly regarding the presence of a distal aortic neck. Cinefluoroscopy was used in all patient and was particularly useful for determining the continuity of vascular structures and the anatomy of branch arteries and for enabling precise positioning of stent devices. Determination of fixation sites and assessing dimensional information by cinefluoroscopy and angiography were limited by inaccuracies produced by image magnification, parallax, and uniplanar views. IVUS was used to determine the morphologic features of vascular structures (i.e., calcium, thrombus), to perform real-time observation of the expansion of devices, and to assure firm fixation of balloon-expanded stents before the procedures were completed. Duplex scanning was very helpful in assessing and identifying precisely the location of arteriovenous fistulas before intervention and provided assessment at follow-up intervals. Three-dimensional reconstruction imaging technologies such as spiral CT were particularly helpful for assessing the morphologic features of vascular anatomy before the intervention and at follow-up intervals, whereas 3-D IVUS provided a similar real-time perspective during the procedure.

Aged↗

PubMed1992

Bilateral adrenal infarction, hypoadrenalism and splinter haemorrhages in the 'primary' antiphospholipid syndrome.

We describe a patient with a 3-year history of recurrent deep vein thromboses (DVT) of the lower limbs, who developed adrenal insufficiency following withdrawal of warfarin therapy. Multiple splinter haemorrhages of the nail beds were evident, simultaneous with the development of adrenal infarction in the absence of infective endocarditis. CT scans of the adrenal glands were consistent with bilateral adrenal infarctions. The patient had persistently high titres of IgG anticardiolipin antibodies (aCL) over the previous 4 years in the absence of antinuclear antibodies (ANA), antibodies to double stranded deoxyribonucleic acid (dsDNA) or extractable nuclear antigens (ENA). Thrombocytopenia and an intermittently positive Coombs' test had been noted. Previous episodes of DVT were associated with inadequate warfarin control and a period of warfarin resistance. He conforms to a diagnosis of a 'primary' antiphospholipid syndrome.

Adrenal Gland Diseases↗

PubMed1987

A matched pairs comparison of cycle ergometry and treadmill exercise testing in the evaluation of coronary heart disease.

In 105 patient pairs, matched for sex, aged within a ten-year range and with closely similar coronary disease, the sensitivity and specificity of treadmill testing using the Bruce Protocol was compared to cycle ergometry using the 100 kpm/min (16 W/min) increment protocol, and found to be similar. The parameters of use were ST segment depression (sensitivity of 52% for treadmill and 61% for cycle), test angina (65% and 61%), significant work impairment (66% and 68%) and impaired blood pressure response (31% and 20%). The sensitivity was increased (treadmill to 84%, cycle to 89%) if the four parameters were grouped, and abnormality in any one of them was regarded as a positive test. The equivalent severity of coronary disease resulted in more severe work impairment on the cycle than on the treadmill. The mean work level of the treadmill group was 80%, and of the cycle group, 61% of their respective, nomographically predicted, normal values. The difference was similar for the zero, single and multivessel disease groups. This difference should be recognised when comparing the two techniques.

Angina Pectoris↗

PubMed1985

Effect of ketanserin on blood pressure and biochemical parameters in patients with essential hypertension.

Seventeen subjects with essential hypertension (14 men, 3 women, 40-69 years of age), 13 of whom continued their previous antihypertensive therapy, completed a double-blind crossover trial of ketanserin 40 mg twice daily versus placebo tablets twice daily. Each treatment phase was 6 weeks in duration. For the group as a whole, blood pressure (BP) was reduced in the ketanserin phase compared with the placebo phase: supine mean BP decrease: 4 +/- 1 mm Hg (p less than 0.05); standing mean BP decrease: 7 +/- 1 mm Hg (p less than 0.001). Heart rate (HR) was also significantly decreased in the ketanserin phase (5 +/- 1 beats/min) (p less than 0.001). When individual subgroups were analysed, the reductions in BP and HR were greater in subjects already receiving antihypertensive therapy, diuretics, and/or beta-adrenergic blockers. Changes were observed in 24-h urine sodium and potassium excretion: Sodium (mmol/day): placebo 137 +/- 17, ketanserin 174 +/- 19 (p less than 0.05); potassium (mmol/day): placebo 74 +/- 8, ketanserin 57 +/- 5. For the group as a whole, there were no significant adverse effects during the ketanserin phase, although two subjects had a dose reduction of ketanserin because of drowsiness and dizziness. Two additional subjects withdrew from the study owing to adverse effects, one in the placebo phase. In conclusion, ketanserin in the dose administered has a modest hypotensive effect, which is best seen in subjects already receiving other antihypertensive agents.

Adrenergic beta-Antagonists↗

PubMed1984

True sensitivity of cardiac exercise testing. A combined clinical evaluation of multiple parameters.

Maximal exercise tests were performed in 308 patients with angiographically defined coronary disease, in 38 patients whose coronary vessels were not obstructed, and in 236 clinically normal volunteers. The sensitivity of parameters indicating ischaemia was evaluated singly and in combination in each group. The most sensitive individual parameters were work capacity restriction (65%), ST segment depression (56%) and test angina (55%). When the sequence of parameters were assessed successively in the coronary group, the sensitivity rose from 56% with ST depression to 70% with the addition of test angina, to 85% when work capacity restriction was added, and to 87% when inadequate heart rate or blood pressure responses or repetitive ventricular arrhythmias were included. In the group of patients whose coronary vessels were not obstructed, substantial clinical abnormalities and a bias to carry out angiography in those with abnormal exercise responses led to false ST segment changes in 34%, and, in a further 20%, to positivity in the other parameters. In clinically normal subjects a 15% "false" positive rate occurred. One parameter (R wave amplitude change) was falsely positive in 24%, and was therefore excluded. Grouped parameter sensitivity for patients who exercised on a bicycle and those who used a treadmill was similar.

Coronary Disease↗

PubMed1984

The effect of ketanserin on blood pressure and biochemical parameters in treated patients with essential hypertension.

17 subjects with essential hypertension (14 male, 3 female - ages: 40-69 years), 13 of whom continued their previous anti-hypertensive therapy, completed a double-blind cross-over trial of ketanserin 40 mg twice daily versus placebo tablets twice daily - each treatment phase was six weeks in duration. For the group as a whole, blood pressure (BP) was reduced in the ketanserin phase compared with the placebo phase; supine mean BP decrease: 4 +/- 1 mm Hg (p less than 0.05); standing mean BP decrease: 7 +/- 1 mm Hg (p less than 0.001). Heart rate (HR) was also significantly decreased in the ketanserin phase by 5 +/- 1 beats/minute (p less than 0.001). When individual subgroups were analysed the reductions in BP and HR were greater in subjects already receiving anti-hypertensives, diuretic and/or beta blockers. Changes were observed in 24 hour urine sodium and potassium excretion - sodium (mmol/day): placebo 137 +/- 17, ketanserin 174 +/- 19 (p less than 0.05); potassium (mmol/day): placebo 74 +/- 8, ketanserin 57 +/- 5. For the group as a whole there were no significant adverse effects during the ketanserin phase, although two subjects had a dose reduction of ketanserin because of drowsiness and dizziness. Two additional subjects withdrew from the study due to adverse effects, one in the placebo phase. In conclusion ketanserin in the dose administered has a modest hypotensive effect which is best seen in subjects already receiving other anti-hypertensive agents.

Adrenergic beta-Antagonists↗