Biomedical subjects

D J Minion

Publications and source records attributed to D J Minion.

8 recordsLinked to original sources

PubMed1997

Platelet-derived growth factor production by cells from Dacron grafts implanted in a canine model.

PURPOSE: Previous studies of grafts implanted in dogs documented a time-dependent increase in platelet-derived growth factor (PDGF) production that correlated with inner-capsule thickness. The purpose of this study was to identify the cells in vascular grafts that produce PDGF. METHODS: Dacron thoracoabdominal grafts were seeded with autologous endothelial cells (ECs), implanted in 11 beagles, and removed after 4 or 20 weeks. ECs and smooth muscle cells (SMCs) were cultured from grafts and adjacent aorta, and PDGF in the conditioned media was measured by radioreceptor assay. The PDGF A-chain mRNA level in freshly harvested cells was assessed using reverse transcriptase, followed by polymerase chain reaction, and expressed as a ratio of glyceraldehyde-3-phosphate dehydrogenase signal. Localization of PDGF A-chain and B-chain protein was also examined with immunohistochemical analysis. RESULTS: Graft and aortic ECs in primary culture did not produce significantly different amounts of PDGF in 72 hours, averaging 368 +/- 160 and 340 +/- 81 pg/microgram DNA, respectively. Graft SMCs in primary culture produced significantly more PDGF than aortic SMCs (584 +/- 343 and 113 +/- 94 pg/microgram DNA, respectively; p < 0.01). Graft SMC PDGF secretion remained greater than aortic SMC PDGF secretion through at least six cell passages. PDGF A-chain mRNA levels were not significantly different for aortic or graft ECs. The PDGF A-chain mRNA level was significantly higher for graft SMCs than aortic SMCs (2.44 +/- 0.67 and 1.45 +/- 0.57 pg/microgram, respectively; p < 0.03). Immunocytochemical analysis detected PDGF A-chain and B-chain protein in the ECs from both native aorta and graft as well as the subendothelial SMCs in the graft, but not in the SMCs of the native aorta. CONCLUSIONS: These results suggest that graft SMCs are functionally altered, producing more PDGF than aortic SMCs. PDGF produced by graft SMCs may contribute to the development of intimal hyperplasia.

Animals↗

PubMed1996

Inhibition of smooth muscle cell proliferation and migration in vitro by antisense oligonucleotide to c-myb.

PURPOSE: Smooth muscle cell (SMC) migration and proliferation are prominent features of intimal hyperplasia. Previous studies have shown that inhibition of c-myb inhibits arterial SMC proliferation. Our goal was to evaluate the effect of an antisense oligonucleotide targeted to c-myb on the proliferation and migration of SMC explanted from synthetic vascular grafts. METHODS: SMCs were enzymatically removed from aortas and Dacron grafts explanted from dogs (n = 5). For proliferation studies, quiescent SMCs were incubated with either 0.0, 0.5, 5.0, or 10.0 microM antisense (GTGTCGGGGTCTCCGGGC) or sense (GCCCGGAGACCCCGACAC) oligonucleotides to c-myb. Proliferation was measured after 24 hours by incorporation of [3H]thymidine. Migration was assessed 24 hours after a razor injury. RESULTS: Antisense to c-myb consistently inhibited proliferation and migration of both native aortic and graft SMCs in a dose-dependent fashion. At a concentration of 10 microM antisense oligonucleotide, aortic and graft SMC proliferation rates were 32% +/- 20% and 56% +/- 9% of control samples, respectively. At 25 microM antisense, the number of migrating aortic and graft SMCs decreased to 41.9% +/- 26.8% and 51.9% +/- 34.1% of control samples, respectively. CONCLUSIONS: Our results suggest that antisense oligonucleotides to c-myb may be useful in the inhibition of SMC proliferation and migration associated with development of intimal hyperplasia.

Animals↗

PubMed1994

Elastin is increased in abdominal aortic aneurysms.

The decrease in elastin concentration in abdominal aortic aneurysm (AAA) has been ascribed to elastolysis. The discordant response of the elastin and collagen genes in AAA suggests a different explanation: dilution of elastin because of higher levels of synthesis of collagen and other matrix proteins. The purpose of this study was to determine circumferential content of elastin, collagen, and total protein in aneurysmal (AAA), atherosclerotic, and normal (NL) infrarenal aorta. Standard serial extraction techniques of complete 1-cm rings of midinfrarenal aortic tissue were used to remove soluble protein, calcium, and lipids. Hydroxyproline (collagen), desmosine/isodesmosine (elastin), and total amino acid (total protein) content were determined by amino acid analysis. Means values (+/- SEM) were compared by ANOVA. Circumferential content of desmosine/isodesmosine was increased 2.5-fold in AAA compared to NL (P < 0.05). Collagen and total protein were increased 5.7- and 4.7-fold, respectively (P < 0.05). There was a high degree of correlation between circumference and collagen content (r = 0.89). These data demonstrate that significant synthesis of matrix proteins accompanies aortic dilatation. While both elastin and collagen are increased, there is a much greater increase in circumferential collagen content than elastin content. These data do not preclude proteolysis as a factor in AAA but suggest that the decrease in elastin concentration results from dilution of elastin by a greater increase in the synthesis of other matrix proteins and that synthesis is an important factor in AAA formation.

Adult↗

PubMed1994

Abdominal aortic aneurysms are associated with altered matrix proteins of the nonaneurysmal aortic segments.

PURPOSE: Abdominal aortic aneurysms (AAA) are associated with diffuse arteriomegaly and peripheral aneurysms, suggesting a generalized process. Elastin and collagen are the key structural proteins of the aorta, and their relative content is markedly altered in tissue from AAA. Our purpose was to investigate elastin and collagen content in the proximal, nonaneurysmal segments of aortas with infrarenal AAA. METHODS: After extraction of lipid, calcium, and soluble proteins, hydroxyproline (collagen) and desmosine-isodesmosine (elastin) contents were determined by high-performance liquid chromatography in the ascending and descending thoracic, supraceliac, and suprarenal aorta. By repeated measures of analysis of covariance, collagen was found to be increased throughout the aorta in AAA as compared with normal aorta or aorta with atherosclerotic occlusive disease. This difference remained significant when adjustments were made for group differences in age and degree of atherosclerosis. This increase in collagen content results in a dilutional decrease in elastin concentration. These data demonstrate that the same matrix protein alterations found in AAA tissue occur throughout the aorta, differing only in magnitude in the aneurysmal and nonaneurysmal segments. These data suggest that aneurysm formation may related to alterations in the regulation of elastin and collagen.

Adult↗

PubMed1994

Pseudoaneurysm of the external carotid artery following radical neck dissection and irradiation: a case report and review of the literature.

A 54-year-old man developed a pseudoaneurysm of the left external carotid artery 8 years after concluding treatment for squamous cell carcinoma of the tongue. Treatment included radiation therapy, radical neck dissection and a myocutaneous pectoralis major flap. Percutaneous transcatheter embolization resulted in thrombosis of the pseudoaneurysm. A review of the literature yielded only six other reported cases of pseudoaneurysm of the external carotid artery proper.

Aneurysm↗

PubMed1993

Rational approach to postoperative transfusion in high-risk patients.

An appropriate threshold for transfusion in patients with coronary artery disease has not been defined. Our purpose was to determine: (1) the effects of preoperative volume loading; (2) postoperative function and oxygen delivery (DO2); (3) an appropriate transfusion threshold based on observed DO2 in high-risk patients undergoing abdominal aortic aneurysm (AAA) repair, bypass of aortoiliac disease (AOD), distal bypass, or carotid endarterectomy (CEA). Preoperative volume loading increased cardiac output (CO) in all groups by 15% to 22%. Postoperative CO was unchanged from optimal preoperative values except in the CEA group, in which it decreased. Systemic vascular resistance decreased in the AAA and AOD groups. The decrease in postoperative DO2 in all groups (25% to 31%) was related to a decrease in hemoglobin. Despite marginal (less than 11 mL/kg/min) postoperative DO2 in more than a third of patients, there was no compensatory increase in CO. Thus, after optimization of function by volume loading, red cell transfusion may be the only way to increase DO2. Hemoglobin levels of 10 to 12 g/dL may be required for adequate DO2 when ventricular function is markedly impaired.

Aortic Aneurysm, Abdominal↗

PubMed1993

Elastin and fibrillin mRNA and protein levels in the ontogeny of normal human aorta.

Elastin associated microfibrils (EAMF) are ubiquitous connective tissue structures that are believed to provide tensile strength and flexibility to numerous tissues. In this study the ontogeny of EAMF in normal human aorta was examined using immunohistochemical analysis of fibrillin, an EAMF component, and mRNA levels of fibrillin and elastin. Specimens of infra-renal aorta from ages 11 months to 44 years were obtained following organ procurement. Decreasing amounts, as judged by computer digitized image analysis, of immunoreactive fibrillin when compared to elastin auto-fluorescence were observed in aortic sections with increasing age. Elastase treatment would un-mask the anti-fibrillin reactive epitope reinforcing the suggestion that EAMF act as a "scaffold" for elastin deposition. Northern and dot blot hybridizations demonstrated a decrease in relative fibrillin message levels with increasing age. The abundance of fibrillin in relation to elastin may suggest a role for EAMF independent of their association with elastin.

Actin Cytoskeleton↗

PubMed1993

Soluble factors modulate changes in collagen gene expression in abdominal aortic aneurysms.

BACKGROUND: Although increased procollagen gene expression and synthesis have been implicated in the progression of abdominal aortic aneurysms (AAA), factors modulating this change have not been identified. Furthermore, it is not known whether the increase in AAA procollagen expression is specific to this disease or also occurs in tissue affected by atherosclerotic occlusive disease (AOD). If paracrine rather than autocrine factors are responsible for increased gene expression in AAA, this effect should be transferable to target smooth muscle cells through conditioned media. Our objectives were to determine 1 alpha (I) procollagen messenger RNA levels in AOD tissue compared with normal and AAA and to determine whether differences noted in tissue procollagen gene expression could be transferred through conditioned media from normal, AOD, and AAA tissues to target smooth muscle cells in primary culture. METHODS: Normal, AOD, and AAA tissue was used for tissue RNA extraction or was minced and washed with serum-free media (4 degrees C) x 30 minutes and the media applied to human aortic smooth muscle cells (SMC) in primary culture for 36 hours. Total RNA from tissue and SMC exposed to conditioned media was analyzed by Northern and dot blot analysis for 1 alpha (I) procollagen. RESULTS: Relative tissue 1 alpha (I) procollagen levels were not increased in AOD (0.23 +/- 0.05) as compared with normal (0.17 +/- 0.03); both were decreased compared with AAA (0.53 +/- 0.07; p < 0.01). The 1 alpha (I) procollagen levels in SMC exposed to conditioned media from AAA (1.73 +/- 0.15) were increased (p < 0.05) compared with AOD (1.10 +/- 0.12) and normal (1.16 +/- 0.16). CONCLUSIONS: There is no increase in tissue AOD procollagen gene expression. The ability to transfer the same relative patterns of gene expression from tissue to target SMC with conditioned media suggests that paracrine, rather than autocrine, factors modulate procollagen expression in AAA tissues.

Adult↗