Search PubMed⌕ Search

Biomedical subjects

C Rogers

Publications and source records attributed to C Rogers.

At least 73 records · Page 4Linked to original sources
PubMed1999

Balloon-artery interactions during stent placement: a finite element analysis approach to pressure, compliance, and stent design as contributors to vascular injury.

Endovascular stents expand the arterial lumen more than balloon angioplasty and reduce rates of restenosis after coronary angioplasty in selected patients. Understanding the factors involved in vascular injury imposed during stent deployment may allow optimization of stent design and stent-placement protocols so as to limit vascular injury and perhaps reduce restenosis. Addressing the hypothesis that a previously undescribed mechanism of vascular injury during stent deployment is balloon-artery interaction, we have used finite element analysis to model how balloon-artery contact stress and area depend on stent-strut geometry, balloon compliance, and inflation pressure. We also examined superficial injury during deployment of stents of varied design in vivo and in a phantom model ex vivo to show that balloon-induced damage can be modulated by altering stent design. Our results show that higher inflation pressures, wider stent-strut openings, and more compliant balloon materials cause markedly larger surface-contact areas and contact stresses between stent struts. Appreciating that the contact stress and contact area are functions of placement pressure, stent geometry, and balloon compliance may help direct development of novel stent designs and stent-deployment protocols so as to minimize vascular injury during stenting and perhaps to optimize long-term outcomes.

Animals↗
PubMed1999

Endothelial implants inhibit intimal hyperplasia after porcine angioplasty.

The perivascular implantation of tissue-engineered endothelial cells around injured arteries offers an opportunity to study fundamental vascular physiology as well as restore and improve tissue function. Cell source is an important issue because the ability to implant either xenogeneic or allogeneic cells would greatly enhance the clinical applications of tissue-engineered grafts. We investigated the biological and immunological responses to endothelial cell xenografts and allografts in pigs 4 weeks after angioplasty of the carotid arteries. Porcine or bovine aortic endothelial cells were cultured within Gelfoam matrices and implanted in the perivascular space of 42 injured arteries. Both porcine and bovine endothelial cell grafts reduced the restenosis index compared with control by 54% and 46%, respectively. Perivascular heparin release devices, formulated to release heparin at twice the rate of release of heparan sulfate proteoglycan from endothelial cell implants, produced no significant reduction in the restenosis index. Endothelial cell implants also reduced occlusive thrombosis compared with control and heparin release devices. Host immune responses to endothelial implants were investigated by immunohistochemical examination of explanted devices and by immunocytochemistry of serum samples. The bovine cell grafts displayed infiltration of leukocytes, consisting primarily of lymphocytes, and caused an increase in antibodies detected in serum samples. Reduced cellular infiltration and no humoral response were detected in animals that received allografts. Despite the difference in immune response, the biological effects of xenografts or allografts did not differ significantly.

Angioplasty↗
PubMed1999

Measuring arterial strain induced by endovascular stents.

Endovascular stents are expandable, fenestrated tubes that are threaded in their collapsed state through an artery to a site of occlusion, plastically enlarged and left as permanent implants to scaffold the artery open. The stent induces large-scale vascular strains that are difficult to measure in vivo and yet can be critical determinants of stent-vessel biology. A method is developed to measure the strain tensor developed on the surface of an artery as a stent is expanded in vivo. Arterial sections are marked with reference points and imaged as the stent is expanded. An axially symmetric parametric model of the artery is determined for each expansion time-point, and these reference points are back-projected onto this surface. The back-projected reference points are grouped and analysed to determine the circumferential, axial and torsional strain tensor components in each arterial subsection. The method is characterised in vitro using bovine artery segments and a latex phantom, and is then tested on rabbits to demonstrate its feasibility in vivo. In vitro experiments on stented bovine arteries show typical post-stenting strains of 0.60, -0.26, and 0.08 mm mm-1 in the circumferential, axial and torsional directions, respectively, sampled every 1 mm along the length of the stented region. Phantom experiments characterise the RMS error of system measurements as 0.1 mm mm-1. The system is shown capable of measuring strains of straight, accessible vessels in the presence of respiratory/cardiac motion and visual glare in vivo.

Animals↗
PubMed1999

Randomized clinical trial of early laparoscopy in the management of acute non-specific abdominal pain.

BACKGROUND: Abdominal pain of uncertain aetiology (non-specific abdominal pain; NSAP) is the commonest reason for emergency surgical admission. The aim of this study was to examine the role of early laparoscopy in the management of NSAP. METHODS: Some 120 patients, admitted between November 1995 and October 1998 with acute abdominal pain of uncertain aetiology, were randomized into two groups: group 1 had laparoscopy during the first 18 h of admission and group 2 had close observation, conventional investigation and surgical intervention if signs of peritonism developed. Outcome measures were diagnosis, operative procedures, duration of hospital stay, readmission rate, morbidity and death, patient satisfaction and total number of investigations performed. RESULTS: Median hospital stay was 2 (range 1-13) days in both groups (P = 0.87). A diagnosis was established in 48 (81 per cent) of 59 patients in group 1 compared with 22 (36 per cent) of 61 in group 2 (P < 0.0001). The morbidity rate was 14 (24 per cent) of 59 in group 1 and 19 (31 per cent) of 61 in group 2 (P = 0.3629). The readmission rate at a median follow-up of 21 (range 1-35) months was 17 (29 per cent) of 59 in group 1 compared with 20 (33 per cent) of 61 in group 2 (P = 0. 6375). Well-being scores improved from 134 on admission to 149 of 177 6 weeks later in group 1 (P = 0.007) and from 132 to 143 of 177 in group 2 (P = 0.089). CONCLUSION: Early laparoscopy provided a higher diagnostic accuracy and improved quality of life in patients with NSAP.

Abdominal Pain↗
PubMed1999

Factors predicting cesarean delivery for American Indian women in New Mexico.

BACKGROUND: American Indian women have one of the lowest cesarean delivery rates among all ethnic groups evaluated in the United States. Our objective was to identify risk factors for cesarean delivery among American Indian women in New Mexico. METHODS: Live birth certificate data (1994) from the New Mexico Bureau of Vital Records and Health statistics were used to compare American Indian women who had a cesarean delivery with those who had a vaginal delivery. We examined demographic, prenatal, and intrapartum factors to determine risk factors for cesarean delivery. RESULTS: In 1994 American Indian women in New Mexico had a cesarean delivery rate of 12 percent. Risk factors for cesarean delivery included age equal to or over 35 years (OR = 1.8, 1.3-2.5) and nulliparity (OR = 1.9, 1.5-2.5). Obstetric risk factors included prematurity (OR = 2.3, 1.5-3.6), low birthweight (OR = 2.6, 1.7-4.2), diabetes (OR = 1.7, 1.1-2.5), pregnancy-induced hypertension (OR = 2.6, 1.8-3.8), and labor and delivery complications (OR = 9.5, 7.5-12.1). Age less than 20 years was negatively associated with cesarean delivery (OR = 0.5, 0.3-0.7). CONCLUSION: American Indian women have risk factors for cesarean delivery that are similar to those reported in other populations. Future prospective research evaluating intrapartum management may help identify reasons for the low cesarean birth rate.

Adult↗
PubMed1999

Distribution of D1S80 alleles in the Bahrainian population.

This study demonstrates that the locus D1S80 is highly polymorphic in the Bahrainian population. There were 24 different D1S80 alleles and 51 distinct genotypes observed in 198 Bahrainians. There was one allele observed that was smaller than the 14 repeat allele. This data set meets the Hardy-Weinberg expectations (HWE) and could be a useful marker for parentage testing and forensic applications.

Alleles↗
PubMed1998

FG syndrome: report of three new families with linkage to Xq12-q22.1.

FG syndrome is a rare X-linked recessive form of mental retardation, first described by Opitz and Kaveggia in 1974 in five related males with mental retardation, disproportionately large heads, imperforate anus, and congenital hypotonia. Partial agenesis of the corpus callosum was noted in at least one of the initial cases and has been seen in a number of subsequently-reported cases. The associated congenital hypotonia with joint hyperlaxity tends to progress to contractures with spasticity and unsteady gait in later life. The presence of subtle facial abnormalities and the characteristic behavior in midchildhood facilitate diagnosis at this age, particularly when there are other affected male relatives in the maternal family. Recently, Briault et al. [1997] mapped a gene for FG syndrome to the Xq12-q21.31 region. We describe three additional families (six additional patients) with FG syndrome on whom we have conducted linkage analysis. Our findings support the localization of a gene for the FG syndrome in Xq12-q21. In addition, we have noted skewed X-inactivation in carrier females, as well as new associated findings in affected males of sagittal craniosynostosis and split hand malformation.

Abnormalities, Multiple↗
PubMed1998

A mAb to the beta2-leukocyte integrin Mac-1 (CD11b/CD18) reduces intimal thickening after angioplasty or stent implantation in rabbits.

Leukocytes are recruited early and abundantly to experimentally injured vessels, in direct proportion to cell proliferation and intimal growth. Activated circulating leukocytes and Mac-1 (CD11b/CD18, alphaMbeta2) expression are markers of restenosis risk in patients undergoing angioplasty. As angioplastied vessels lack endothelium but have extensive fibrin(ogen) and platelet deposition, we hypothesized that Mac-1-dependent adhesion to fibrin(ogen) is an important determinant of leukocyte recruitment and function, which may in turn promote intimal growth. To study this hypothesis we administered M1/70, an anti-CD11b blocking mAb, to rabbits (1 mg/kg i.v.) immediately before, and every 48 hr for 3, 6, or 14 days after, iliac artery balloon denudation or deeper stent-induced injury. M1/70, which bound to isolated rabbit monocytes and dose-dependently inhibited Mac-1-mediated fibrinogen binding in vitro, reduced leukocyte recruitment more than 2-fold 3, 6, and 14 days after injury. Neointimal growth 14 days after injury was markedly attenuated by treatment with M1/70 (intimal area after balloon injury, 0.12 +/- 0.09 mm2, compared with 0.32 +/- 0.08 mm2 in vehicle-treated controls, P < 0.01, and 0.38 +/- 0.08 mm2 in IgG-treated controls, P < 0.005; intimal area after stent injury, 0. 56 +/- 0.16 mm2, compared with 0.84 +/- 0.13 mm2 in vehicle-treated controls, P < 0.05, and 0.90 +/- 0.15 mm2 in IgG-treated controls, P < 0.02). Mac-1 blockade reduces experimental neointimal thickening, suggesting that leukocyte recruitment to and infiltration of injured arteries may be a valid target for preventing intimal hyperplasia.

Angioplasty, Balloon↗
PubMed1998

Pathobiologic responses to stenting.

As the interventions available to treat obstructive coronary artery disease become increasingly complex, our understanding of the vascular response to these interventions requires greater sophistication. Molecular and cellular biologic tools have now propelled us into another phase of work with vascular devices. Initially, studies of endovascular implants such as stents focused on developing models of vascular injury. With these models, we could then examine the designs of individual stents and connect structure with performance. Now we are entering a third phase in which stent manufacturers are looking to science to dictate stent design.

Angioplasty, Balloon, Coronary↗
PubMed1998

Successful redeployment of an unexpanded coronary stent.

We report on treatment of a patient in whom failure to deploy the distal portion of a Palmaz-Schatz stent occurred but was not recognized. After an unstable course, the patient underwent repeat coronary angiography, at which time the stent was rewired and redilated. Full deployment of the stent with restoration of TIMI grade 3 flow was achieved. The putative cause of the problem, incomplete deployment of the stent because of inadvertent advancement of the stent delivery sheath, should be avoided, and needs to be recognized if it occurs. Crossing and redilating the stent is possible, although technically difficult.

Adult↗
PubMed1998

Dynamic thermomechanical properties and crystallinity of ultrahigh molecular weight polyethylene tibial inserts.

A dynamic thermomechanical analysis method was used to determine the values of the viscoelastic parameters, storage modulus (E') and the tangent of the loss angle (tan delta) of samples taken from the near surface and core regions of ultrahigh molecular weight polyethylene (UHMWPE) bar stock specimens that had been aged in ambient laboratory air for 12 months (the control group) and UHMWPE tibial inserts that had been subjected to the following treatments: gamma sterilization followed by shelf aging in ambient laboratory air for between 56 and 112 months or ethylene oxide (EtO) gas sterilization followed by shelf aging in ambient laboratory air for 73 months. Differential scanning calorimetry was used to determine the melt temperature and percentage crystallinity (%C) of these samples. There were three main findings. First, EtO sterilization produced no statistically significant effect on the values of E' or tan delta (relative to those for the control group), but the values of these parameters were markedly affected by gamma sterilization. Second, for gamma-irradiated samples, E' increased with an increase in the shelf aging time. Third, there was a strong direct association between E' and % C. The various potential uses of this association are described, paying special attention to its likely role in predicting the in vivo wear of UHMWPE tibial inserts.

Biocompatible Materials↗
PubMed1998

Paradoxical response to photorefractive treatment for postkeratoplasty astigmatism.

A 42-year-old woman with functionally disabling postkeratoplasty astigmatism in her right eye 3 years after corneal transplantation for keratoconus received photorefractive keratectomy for high astigmatism in that eye. This did not reduce her astigmatism. The procedure was repeated and corneal astigmatism paradoxically increased. The forces within the pseudo-optical ring that cause and maintain astigmatism in corneal transplants may be a significant factor in the unpredictable response of some corneal transplants to excimer photorefractive astigmatism correction.

Adult↗
PubMed1998

The biologic effects of growth factor-toxin conjugates in models of vascular injury depend on dose, mode of delivery, and animal species.

Toxin-conjugates, complexes designed from the fusion of tissue toxins and pathology-specific ligands, offer the potential for targeted cytotoxic therapy. Some have postulated that the recurrent failure of these conjugates to exhibit benefit in animal models of vascular injury arose because the timing and frequency of conjugate delivery were insufficient to meet the demands of the arterial wall. Previous data suggest that increasingly frequent dosing would lead to superior inhibition of intimal hyperplasia. We now report on the biological effects of the controlled release of a recombinant conjugate of basic fibroblast growth factor (bFGF) and the plant toxin saporin (SAP), bFGF-SAP. Alginate/heparin-Sepharose microspheres and films were designed as drug carriers to control release the bFGF-SAP conjugate or bFGF alone in small doses. When bFGF-SAP-incorporated microspheres or films were implanted adjacent to balloon angioplastied porcine carotid arteries, the controlled release of bFGF-SAP over the four-week study stimulated rather than inhibited hyperplasia. When these same devices were used in cell culture, unexpected findings were produced. bFGF-SAP reduced in vitro bovine vascular smooth muscle cell growth at high concentrations (1-10 microgram/mL) but increased smooth muscle cell growth at lower concentrations (up to 1 microgram/mL). Microsphere controlled-released bFGF-SAP ( approximately 60 ng/mL over 4 days) stimulated the growth of smooth muscle cells more than any of the tested bolus applications of the conjugate. These data provide cause to reconsider our acceptance of controlled release technology as the answer to all forms of drug delivery problems, and to apply more rigorous means of matching the kinetics of drug delivery to the kinetics of the vascular response to injury.

Angioplasty↗
PubMed1998

Contracting for clinical genetic services: the Welsh model.

In a time of increasing competition for clinical services resources, it is imperative that health professionals actively participate in the commissioning process in order to ensure that established clinical standards are not compromised. Introduction of the NHS reforms in the UK in the early 1990s highlighted the difficulties in contracting for a specialised service such as clinical genetics, especially in the absence of a consensus regarding the contract currency. An average block contract price for each new family referred was introduced in Wales in 1992, and data from the subsequent five years show that this charging system is economically feasible and has the advantages of (1) recognising the contribution to care of non-medical personnel on the genetics team, (2) covering follow up including the counselling of relatives, (3) protecting the service from loss of income owing to non-attendance, and (4) providing a basis for negotiation when new services are being proposed to purchasers. Activity data show that while the majority of conditions incur below average cost, the mean cost is influenced by a small number of autosomal dominant and X linked disorders. The cost risk to the provider for seeing families over an extended period is minimal, as the data establish that family files experience an exponential decrease in activation probability over the early years, but this becomes constant later on. The robustness of the system is dependent on accurate baseline data on referral patterns to the service, recording of activity, and staff costs.

Contract Services↗
PubMed1998

Positive relationship of cortisol concentrations and oral nutrition to epidermal growth factor concentrations in preterm infants.

We have suggested from previous studies that increases in early neonatal epidermal growth factor (EGF) concentrations were dependent on adequate glucocorticoid hormone concentrations. In order to examine this relationship, matched values for cortisol and EGF in 193 preterm infants on days 2 and 6 were compared. Gestational age had a significant positive effect on EGF concentrations for those infants receiving oral nutrition and there was also a positive relationship between nutrition and cortisol concentration. Cortisol was then used as an independent factor and was significantly (p = 0. 01) related to EGF values such that as cortisol concentrations increased, EGF values also increased. In summary, we suggest that these results are consistent with a role for cortisol in the control of the EGF pattern in the newborn period.

Aging↗