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Biomedical subjects

J D Cameron

Publications and source records attributed to J D Cameron.

At least 55 records · Page 3Linked to original sources
PubMed1997

Arterial compliance increases after moderate-intensity cycling.

Exercise training elevates arterial compliance at rest, but the effects of acute exercise in this regard are unknown. This study investigated the effects of a single, 30-min bout of cycling exercise at 65% of maximal oxygen consumption on indexes of arterial compliance. Whole body arterial compliance determined noninvasively from simultaneous measurements of aortic flow and carotid pressure was elevated (66 +/- 26%) at 0.5 h postexercise (P = 0.04), followed by a decline to baseline 1 h after exercise. Aortic pulse-wave velocity, which is inversely related to compliance, was reduced (4 +/- 2%; P = 0.04) at 0.5 h postexercise. Pulse-wave velocity in the leg decreased by 10 +/- 4% at this time (P = 0.01). Mean arterial pressure was unchanged; however, central systolic blood pressure was reduced postexercise (P = 0.03). Cardiac output was elevated after exercise (P = 0.007) via heart rate elevation (P = 0.001), whereas stroke volume was unchanged. Total peripheral resistance was therefore reduced (P = 0.01) and would be expected to contribute to an elevation in arterial compliance. In conclusion, a single bout of cycling exercise increased whole body arterial compliance by mechanisms that may relate to vasodilation.

Adult↗
PubMed1997

Arterial compliance in obese subjects is improved with dietary plant n-3 fatty acid from flaxseed oil despite increased LDL oxidizability.

The compliance or elasticity of the arterial system, an important index of circulatory function, diminishes with increasing cardiovascular risk. Conversely, systemic arterial compliance improves through eating of fish and fish oil. We therefore tested the value of high intake of alpha-linolenic acid, the plant precursor of fish fatty acids. Fifteen obese people with markers for insulin resistance ate in turn four diets of 4 weeks each; saturated/high fat (SHF), alpha-linolenic acid/low fat (ALF), oleic/low fat (OLF), and SHF. Daily intake of alpha-linolenic acid was 20 g from margarine products based on flax oil. Systemic arterial compliance was calculated from aortic flow velocity and aortic root driving pressure. Plasma lipids, glucose tolerance, and in vitro LDL oxidizability were also measured. Systemic arterial compliance during the first and last SHF periods was 0.42 +/- 0.12 (mean +/- SD) and 0.56 +/- 0.21 units based on milliliters per millimeter of mercury. It rose significantly to 0.78 +/- 0.28 (P < .0001) with ALF; systemic arterial compliance with OLF was 0.62 +/- 0.19, lower than with ALF (P < .05). Mean arterial pressures and results of oral glucose tolerance tests were similar during ALF, OLF, and second SHF; total cholesterol levels were also not significantly different. However, insulin sensitivity and HDL cholesterol diminished and LDL oxidizability increased with ALF. The marked rise in arterial compliance at least with alpha-linolenic acid reflected rapid functional improvement in the systemic arterial circulation despite a rise in LDL oxidizability. Dietary n-3 fatty acids in flax oil thus confer a novel approach to improving arterial function.

Arteries↗
PubMed1997

Biocompatibility of silver-modified polyester for antimicrobial protection of prosthetic valves.

BACKGROUND AND AIMS OF THE STUDY: The biocompatibility of a silver-coated polyethylene terephthlate (PET, polyester) fabric for the inhibition of prosthetic valve endocarditis (PVE) associated with mechanical heart valves (MHVs) was assessed. The infrequency of PVE is outweighed by mortality rates commonly exceeding 50%. These high mortality rates have been attributed to the poor effect of antibiotic therapy on colonized valves and infected myocardial tissue. Silver has been used as an antimicrobial for centuries due to its general effectiveness and relative lack of toxicity. Our previous work has shown PET polyester fabric coated with metallic silver by an ion beam-assisted deposition (IBAD) process to: (i) be effective in vitro in the inhibition of microbial attachment and colonization; (ii) be tightly adherent and low leaching; and (iii) promote tissue ingrowth and the organization of tissue pannus in a short-duration (five weeks) sheep mitral mechanical heart valve model. METHODS: This paper addresses additional biocompatibility assessment consisting of a cell compatibility assay in which serum extracts of silver-coated fabric were exposed to fibroblasts for 48 hours, after which cell viability and function were measured. The amount of silver in the extract was measured using elemental analysis techniques. RESULTS: No signs of toxicity were seen in the cells until the extract concentration reached 1200 p.p.m. Ten-week duration mechanical valve replacement studies in sheep with uncoated or coated polyester sewing cuffs showed comparable tissue ingrowth and mature pannus with a suggestion of a thinner pannus on the silver-coated fabric. Additional antimicrobial testing confirmed the effectiveness of this coating in inhibiting colonization of polyester fabric. CONCLUSIONS: These current results, together with the earlier data, suggest that IBAD silver coating on polyester facilitates healing and may provide protection against PVE.

Animals↗
PubMed1996

Confocal microscopy findings of Acanthamoeba keratitis.

PURPOSE: Tandem scanning confocal microscopy was performed on two patients with Acanthamoeba keratitis to provide images detailing characteristic findings of the disease. Although tandem scanning confocal microscopy of Acanthamoeba has been described in previous reports, Acanthamoeba keratitis has not been fully characterized with this instrument. In vivo confocal micrographs showed the double-walled structure of the Acanthamoeba cyst and associated radial keratoneuritis (perineuritis). METHODS: We reviewed the records of two patients with a clinical diagnosis of Acanthamoeba keratitis, one with culture-proven Acanthamoeba and the other with a suspected Acanthamoeba infection. Slit-lamp biomicroscopy and in vivo tandem scanning confocal microscopy were performed. The images obtained were compared with images from patients without corneal disease. RESULTS: High-contrast round bodies suggestive of Acanthamoeba cysts, as previously described, and irregular forms suggestive of Acanthamoeba trophozoites were found by tandem scanning confocal microscopy. Additionally, we showed conclusively that under certain circumstances (that is, corneal scarring) tandem scanning confocal microscopy can resolve the double-walled structure of the Acanthamoeba ectocyst surrounding the endocyst. Furthermore, radial keratoneuritis was demonstrated, consisting of an irregularly swollen nerve fiber with probable amoebic infiltration. CONCLUSIONS: Confocal microscopy can be a useful, noninvasive imaging technique helpful in the study, diagnosis, and treatment of Acanthamoeba keratitis.

Acanthamoeba↗
PubMed1996

Enhanced vasodilation to acetylcholine in athletes is associated with lower plasma cholesterol.

We investigated a change in vascular reactivity as a potential adaptive mechanism to chronic exercise. The study consisted of 2 separate protocols with 10 male athletes and 10 age-matched sedentary male control subjects participating in each. Protocol 1 investigated forearm blood flow responses to intra-arterial infusions of acetylcholine and sodium nitroprusside by use of venous occlusion plethysmography. Protocol 2 used identical techniques to study responses to norepinephrine, angiotensin II (ANG II), and NG-monomethyl-L-arginine (L-NMMA). The percent reduction in forearm vascular resistance to acetylcholine was significantly greater in the athletic compared with the sedentary group (multivariate analysis of variance for repeated measures, P = 0.03). Covariance analysis suggested that the lower total cholesterol level of the athletic group (P = 0.03) may contribute to their enhanced responsiveness to acetylcholine. There were no differences between athletic and sedentary groups in the forearm vascular resistance responses to norepinephrine, ANG II, sodium nitroprusside, or L-NMMA. These data support the hypothesis that long-term endurance training is associated with enhanced endothelium-dependent dilator reserve due to altered lipoprotein levels in athletes. This finding may have therapeutic application in conditions of elevated cholesterol and impaired vasodilator capacity including hypertension, hypercholesterolemia, atherosclerosis, and cardiac failure.

Acetylcholine↗
PubMed1996

Systemic arterial compliance is decreased in newly-diagnosed patients with coronary heart disease: implications for prediction of risk.

BACKGROUND: Proximal aortic compliance has been shown to be lower in coronary heart disease (CHD) patients compared with healthy matched controls. Assessment of proximal systemic compliance can be performed non-invasively and, therefore, the measurement of proximal compliance may be useful as a risk marker of the likelihood of significant coronary disease. METHODS: Systemic arterial compliance (SAC) and regional aortic stiffness (beta-index of the transverse arch) were measured non-invasively in a group of 20 newly-diagnosed CHD subjects and compared with an otherwise matched control group. These measurements were used to obtain an estimate of the predictive power of mechanical indices in CHD. RESULTS: Significant differences between subjects and controls were found in both SAC and regional aortic stiffness in the absence of differences in blood pressure. Use of loge(SAC) resulted in correct identification of 60% of the cases and 85% of controls. Use of both mechanical indices improved discrimination to 100% for cases, and 87% for controls. Equal likelihood points (case/control), derived from the estimated group distributions, corresponded to loge(SAC) = -1.30 and loge (beta-index) = -2.25. Arbitrarily requiring a 20:1 odds ratio of lack of disease required loge(SAC) > -1.40 and loge (beta-index) < 2.25. For the same odds ratio of presence of disease, loge(SAC) < -2.70 and loge (beta-index) > 3.50 were required. CONCLUSION: Non-invasive assessment of aortic elastic properties is not a definitive diagnostic test for CHD. Our results demonstrate the potential for repeatable, non-invasive methods of assessment of arterial mechanical properties to provide useful additional information for the overall assessment of an individual's cardiovascular risk. Our results also provide a basis for selecting arbitrary break points by which to group subjects in prospective studies.

Aorta↗
PubMed1995

Intravenous chlorpromazine vs intravenous metoclopramide in acute migraine headache.

OBJECTIVE: To compare the efficacy of IV chlorpromazine with that of IV metoclopramide in the treatment for acute migraine headache in the ED. METHODS: A prospective randomized double-blind trial was undertaken at two university-affiliated urban EDs with a combined annual census of more than 85,000 patients. Included in the study were patients presenting to the ED with a diagnosis of migraine headache. The subjects were randomized to receive 0.1 mg/kg/dose IV of either chlorpromazine (CPZ) or metoclopramide (MC), up to a total of three doses. RESULTS: Ninety-one patients completed the protocol; 44 received MC and 47 received CPZ. The demographics of the two groups were similar. Both drugs provided, for the majority of patients, adequate pain relief as measured on a visual analog scale (VAS) completed every 15 minutes from T = 0 minutes to T = 45 minutes. The average pain relief over 45 minutes (delta VAS) for CPZ was 4.87 cm, vs 4.34 cm for MC (p = 0.35). There also was no statistically significant difference in blood pressure (BP) changes (delta BP < 2 mm Hg for both systolic and diastolic BPs, p = 0.47 and 0.33) or numbers of patients reporting adverse effects (AEs) (CPZ: 16 of 35; MC: 13 of 29, p = 0.43). There was no severe AE with either study drug. CONCLUSIONS: Metoclopramide and chlorpromazine administered IV are both effective in the management of acute migraine headache. They are associated with similar minor side-effect profiles.

Acute Disease↗
PubMed1995

Arterial compliance may influence baroreflex function in athletes and hypertensives.

The present study investigated arterial compliance as a possible influence on mean arterial pressure-heart rate (MAP-HR) reflex function in athletes and hypertensives. Aortic stiffness and systemic arterial compliance (SAC) were estimated in 25 elite male athletes and 25 age-matched sedentary controls. Blood pressure did not vary between groups, but SAC was higher in the athletic compared with the sedentary group (0.46 +/- 0.04 vs. 0.37 +/- 0.02 arbitrary compliance units; P = 0.03). In five hypertensives and six age-matched normals and in a subgroup of seven athletes and seven age-matched controls the sigmoidal MAP-HR reflex was assessed using phenylephrine and nitroprusside. In athletes compared with sedentary subjects MAP-HR reflex sensitivity was the same; however, the maximum tachycardia in response to blood pressure reduction was lower in the athletic group (87.1.1 +/- 3.7 vs. 97.1 +/- 2.9 beats/min; P = 0.05). Athletes had a higher blood pressure corresponding to 95% of the HR range (64.2 +/- 3.2 vs. 54.0 +/- 2.1 mmHg; P = 0.02), but there was no difference in the blood pressure corresponding to 5% of the HR range. The blood pressure excursion necessary to traverse the baroreceptor transducer range (MAPd) was therefore less in athletes compared with normals. The beta-index of aortic stiffness correlated closely with MAPd (R = 0.70; P < 0.01). In hypertensives reflex sensitivity was reduced, the minimum HR was elevated, and the MAPd was 56% greater compared with normals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The relationship between arterial compliance, age, blood pressure and serum lipid levels.

OBJECTIVE: To investigate the association of serum lipids with non-invasively assessed systemic arterial compliance in a group of newly diagnosed coronary artery disease patients and their matched controls. DESIGN: Systemic arterial compliance is important in maintaining diastolic blood pressure and coronary perfusion, with decreased diastolic blood pressure in the presence of significant coronary artery disease suggested as contributing to increased morbidity. Decreased systemic arterial compliance is also associated with increased morbidity through its contribution to systolic hypertension. Despite the importance of arterial compliance, its association with biochemical factors is not certain. PATIENTS AND METHODS: Twenty newly diagnosed coronary artery disease patients and disease-free controls were matched for age, sex, smoking status and total serum cholesterol level. Systemic arterial compliance was measured using applanation tonometry and Doppler velocimetry before instigation of treatment. RESULTS: There was no difference in group low-density lipoprotein or high-density lipoprotein cholesterol levels. Systemic arterial compliance was significantly less in the coronary artery disease group. For the groups combined, a significant negative correlation was demonstrated between systemic arterial compliance and low-density lipoprotein; however, on separate group analysis the correlation was confined to the coronary artery disease group. A significant difference was found in the association between systemic arterial compliance and diastolic blood pressure for the two groups. CONCLUSIONS: Increasing low-density lipoprotein cholesterol levels are associated with decreasing systemic arterial compliance; however, the identified intergroup differences suggest that, presumably because of differences in lipid-vessel wall interactions, disease-free subjects exhibit relatively less alteration in aortic mechanical properties than those who develop coronary artery disease.

Age Factors↗
PubMed1994

Ocular and systemic manifestations of encephalocraniocutaneous lipomatosis.

Encephalocraniocutaneous lipomatosis is a congenital neurocutaneous syndrome with epibulbar choristomas and connective tissue nevi of the eyelids as common ophthalmic manifestations. Systemic manifestations occur ipsilateral to the ocular lesions and include lipomas of the cranium and central nervous system, alopecia of the scalp, and abnormalities of the central nervous system. We treated a child with encephalocraniocutaneous lipomatosis who required removal of an epibulbar choristoma. Pathologic evaluation of the epibulbar choristoma in our patient showed the presence of ectopic lacrimal gland tissue and cartilage. Encephalocraniocutaneous lipomatosis should be considered, together with Goldenhar's syndrome and sebaceous nevus syndrome, in the differential diagnosis of conditions associated with epibulbar choristomas.

Cartilage↗
PubMed1994

Exercise training increases total systemic arterial compliance in humans.

Using a noninvasive technique we have investigated the effect of 4 wk of exercise training on total systemic arterial compliance (SAC) in 13 previously sedentary young males. SAC is assessed from simultaneous measurements of ascending aortic blood velocity using Doppler velocimetry and surrogate estimates of aortic root pressure obtained by applanation tonometry of the right carotid artery. Subsequent calibration of the pressure waveform is by linear interpolation against brachial arterial pressures measured sphygmomanometrically. Exercise training increased the overall mean maximum oxygen consumption (VO2 max) by 5.1 ml.min-1 x kg-1 (95% confidence limits 1.30-8.80, P < 0.01) and decreased mean systolic blood pressure by 8.4 mmHg [95% confidence interval (CI) 2.9-13.9, P < 0.01]. Mean SAC increased by 0.26 units (95% CI 0.10-0.43, P < 0.01) with the regional stiffness of the aortic arch (measured echocardiographically using the beta-index) showing a complementary decrease of 1.03 (95% CI -2.25-0.19, P < 0.05). Assuming a logarithmic arterial volume-pressure relationship, we were able to dissociate the change in SAC due to the exercise training-induced decrease in blood pressure from that due to change in the intrinsic compliance of the systemic arteries. Our results indicate that 1) exercise training increases SAC; 2) that the increase in SAC is greater than that due to changes in blood pressure and is likely to include a component due to change in intrinsic arterial compliance; and 3) that the induced change in SAC is linearly related to change in VO2 max.

Adolescent↗
PubMed1994

The decreased adhesion of Y79 retinoblastoma cells to extracellular matrix proteins is due to a deficit of integrin receptors.

PURPOSE: This study was designed to determine whether the Y79 retinoblastoma cell line, a prototype for retinoblastoma cells, exhibits differential adhesive properties toward extracellular matrix (ECM)/basement membrane (BM) proteins compared to normal human retinal (NHR) cells. A second goal was to determine whether differences in adhesion are related to differences in the expression of integrin subunits. METHODS: Y79 cells and NHR cells were tested for their ability to adhere and spread in microtiter wells adsorbed with the ECM/BM proteins laminin, fibronectin, and type IV collagen, as well as fragments of these proteins. The presence of cell surface integrins was determined by flow cytometry, using monoclonal antibodies (mAbs) against integrin subunits. For inhibition assays, cells were preincubated with mAbs against integrin subunits before the adhesion assays. RESULTS: NHR cells adhered to and spread on laminin, fibronectin, and type IV collagen, whereas Y79 cells only adhered moderately to fibronectin. NHR cells expressed high levels of beta 1, alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, and alpha v integrin subunits, and they used these integrin subunits to adhere to all three ECM proteins. In contrast, Y79 cells expressed high levels of only the alpha 4 and beta 1 integrin subunits, used to adhere to fibronectin. CONCLUSIONS: Y79 cells have decreased adhesive capabilities toward ECM/BM proteins, compared to NHR cells. These differences can be attributed, in part, to their significantly lower levels of alpha 1, alpha 2, alpha 3, and alpha 5 integrin subunits, which serve as receptors for type IV collagen, laminin, and fibronectin.

Antibodies, Monoclonal↗
PubMed1993

Assessment of the blood-aqueous barrier by fluorophotometry following poly(methyl methacrylate), silicone, and hydrogel lens implantation in rabbit eyes.

Intraocular lenses of silicone, hydrogel, or acrylic materials that can be implanted through small incisions are being proposed as an alternative to conventional poly(methyl methacrylate) lenses. The potential of each of these materials to stimulate intraocular inflammation is important in their selection as an implantable material. To investigate the potential of each material, we assessed by clinical slitlamp examination, fluorophotometry, and histopathology the inflammatory response induced in the rabbit eye following phacoemulsification and implantation of hydrogel, silicone, or poly(methyl methacrylate) intraocular lenses. All lenses seemed to be equally well tolerated. In general, the degree of inflammation seen clinically decreased over the four-month study; however, anterior segment fluorophotometry showed continued mild interruption of the blood-aqueous barrier in all lens groups. Fluorophotometry is a sensitive method to assess persistent subclinical anterior segment inflammation.

Animals↗
PubMed1993

A case of orbital emphysema as an ocular emergency.

Orbital emphysema is radiologically apparent in 50% of cases of orbital fractures, but it is generally a benign, self-limited condition. However, visual loss may occur if a fracture produces orbital compression via a ball-valve effect, allowing air to enter but not leave the orbit. A case of compressive orbital emphysema complicated by ischemic optic neuropathy is reported. Intraorbital needle aspiration relieved the compression with improvement of visual acuity and normalization of intraocular pressure.

Adult↗
PubMed1993

Characterization of FN-C/H-V, a novel synthetic peptide from fibronectin that promotes rabbit corneal epithelial cell adhesion, spreading, and motility.

PURPOSE: Fibronectin promotes corneal epithelial cell adhesion and motility in vitro and plays an important role in corneal re-epithelialization during corneal wound healing. Multiple domains contribute to the adhesion- and motility-promoting activity of fibronectin. The aim of this study was to identify amino acid sequences that contribute to the rabbit corneal epithelial (RCE) cell adhesion- and motility-promoting activity of the 33 and 66 kD carboxy-terminal heparin-binding fragments of fibronectin. METHODS: Synthetic peptides derived from the 33/66 kD fragments of fibronectin were tested for their ability to directly promote RCE cell adhesion, spreading, and motility. To assess the contribution of these peptides to the activity of fibronectin and the 33/66 kD fragments of fibronectin, synthetic peptides, and antibodies against these peptides were tested for their ability to block RCE cell adhesion, spreading, and motility. RESULTS: In this study, we identified a novel peptide sequence derived from the 33/66 kD fragments of fibronectin, FN-C/H-V (WQPPRARI), that directly promotes the adhesion, spreading, and migration of RCE cells in a concentration-dependent manner. A second peptide from the 33/66 kD fragments of fibronectin, FN-C/H-IV (SPPRRARVT), promoted RCE cell adhesion and spreading, but did not promote RCE cell migration. In contrast, two synthetic peptides from the 33/66 kD fragments of fibronectin that were previously shown to promote RCE cell adhesion (FN-C/H-I and FN-C/H-III) did not promote RCE cell spreading or migration. Soluble FN-C/H-V inhibited RCE cell adhesion to surfaces coated with FN-C/H-V, the 33/66 kD fragments of fibronectin, and to fibronectin. In addition, polyclonal anti-FN-C/H-V IgG inhibited RCE cell adhesion to FN-C/H-V, the 33/66 kD fragments of fibronectin, and to fibronectin. Finally, polyclonal anti-FN-C/H-V IgG also inhibited RCE cell haptotactic migration on the 33/66 kD fragments. CONCLUSIONS: These data suggest that the amino acid sequence defined by peptide FN-C/H-V contributes to the adhesion-, spreading-, and motility-promoting activity of the 33/66 kD carboxy-terminal heparin-binding fragments of fibronectin. Given the important role of fibronectin in corneal wound healing, these findings provide additional insight into the complex molecular basis of corneal epithelial cell interactions with fibronectin and may be important in the context of corneal wound healing.

Amino Acid Sequence↗
PubMed1992

Avellino corneal dystrophy. Clinical manifestations and natural history.

PURPOSE: The pathologic features of a variant of granular corneal dystrophy has been described in which the presence of lattice changes in addition to characteristic granular lesions has been documented. The authors investigated the mode of inheritance, natural history, and clinical manifestations of this dystrophy. METHODS: A family with this condition was investigated, and a pedigree was established. Family members underwent ophthalmic examination, and ophthalmic history was obtained. In addition, pathologic examination of corneal tissue from affected patients was performed. RESULTS: Similar to the four previously described cases, this family also traced its origins to Avellino, Italy. This autosomal dominant condition affected 27 of 92 family members, ranging in age from 5 to 77 years. Granular deposits were the earliest and most common manifestations. Lattice lesions were present in some patients with granular lesions. Older patients had anterior stromal haze between deposits, which impaired visual acuity. Recurrent granular deposits were noted in donor corneal tissue after penetrating keratoplasty for this condition. Pathologic examination of corneal tissue from affected patients confirmed the presence of hyaline material seen in granular dystrophy as well as fusiform deposits of amyloid, similar to those seen in lattice dystrophy type I. CONCLUSION: This study establishes the natural history and clinical manifestations of this condition.

Adolescent↗