Biomedical subjects

Virginia M Miller

Publications and source records attributed to Virginia M Miller.

10 recordsLinked to original sources

PubMed2003

Effect of puberty on coronary arteries from female pigs.

Vascular function changes following loss of ovarian hormones in women at menopause and in experimental animals following surgical ovariectomy. Little is known about changes in vascular function during hormonal transition from sexual immaturity (juvenile) to sexual maturity. Therefore, experiments were designed to determine effects of natural puberty on vascular function in female pigs. Tissue was studied from eight juvenile (2-3 mo) and eight adult (5-6 mo) female pigs. Plasma nitric oxide (NO) was measured, and mRNA for endothelium-derived NO synthase (eNOS) and eNOS protein were determined in aortic endothelial cells. Rings of coronary arteries were suspended for measurement of isometric force in organ chambers. Serum 17beta-estradiol levels were comparable in the two groups, whereas the arithmetic mean of progesterone levels was about two-thirds lower in adults compared with juvenile pigs. Plasma NO was significantly higher in juveniles compared with adults, but mRNA and protein for eNOS were comparable. In coronary arteries, an alpha2-adrenergic agonist caused greater endothelium-dependent relaxations in rings from juvenile compared with adult pigs. Relaxations to bradykinin were similar in arteries from both groups, but inhibition of NO reduced relaxations only in arteries from juvenile pigs. Relaxations from NO were greater in arteries from adult compared with juvenile female pigs. In conclusion, coronary arterial endothelial and smooth muscle responses are selectively modulated at puberty in female pigs. At maturity, plasma NO is reduced and sensitivity of the smooth muscle to exogenous NO is increased. Posttranscriptional regulation of eNOS protein may explain differences in NO bioavailability in juvenile pigs.

Adrenergic alpha-Agonists↗

PubMed2003

Endothelium-dependent responses in coronary arteries are changed with puberty in male pigs.

In humans, cardiovascular disease begins in young adulthood and is more prevalent in males than females. However, little is known about vascular function during transition to adulthood in males. The aim of this study was to define changes in production of endothelium-derived nitric oxide (NO) and coronary arterial responses during puberty. Plasma was collected from juvenile (2-3 mo of age) and adult (5-6 mo of age) male pigs (n = 8/group) for measurement of NO, and aortic endothelial cells were collected for measurement of mRNA and protein for endothelial NO synthase (eNOS). Although plasma NO was higher in juvenile (67.0 +/- 25.6 microM) than in adult (15.0 +/- 7.1 microM) male pigs, eNOS protein was similar in both groups. However, levels of mRNA for eNOS were lower in aortic endothelial cells from juvenile pigs. In rings of coronary arteries suspended in organ chambers for measurement of isometric force and contracted with PGF2alpha, relaxations to an alpha2-adrenergic agonist were significantly inhibited by indomethacin only in juvenile pigs [EC50 (-log M), 6.7 +/- 0.3 with indomethacin and 7.7 +/- 0.3 under control conditions]. NG-monomethyl-l-arginine (l-NMMA) inhibited relaxations in both groups. On the contrary, in the presence of indomethacin, relaxations to bradykinin were inhibited by l-NMMA only in arteries from adult pigs [EC50 (-log M), 8.9 +/- 0.3 with indomethacin and 8.6 +/- 0.3 with addition of l-NMMA]. These results suggest that hormonal changes associated with sexual maturity may affect posttranscriptional and/or translational regulation of eNOS protein and result in lower plasma NO in adult male pigs. In addition, endothelium-derived inhibitory cyclooxygenase products seem to predominate in juveniles.

Animals↗

PubMed2003

Effects of ovariectomy on aggregation, secretion, and metalloproteinases in porcine platelets.

Differences in the aggregation and release of growth factors including matrix metalloproteinases (MMPs) after loss of ovarian hormones could contribute to an exaggerated response to injury in arteries of ovariectomized animals. Therefore, experiments were designed to compare aggregation, dense granular ATP release, expression of MMPs (MMP-2, MMP-9, and MMP-14) and tissue inhibitors of metalloproteinase (TIMP-1 and TIMP-2) in circulating platelets from sexually mature (7 mo old) gonadally intact and ovariectomized (4 wk) female pigs. Numbers of circulating platelets did not change after ovariectomy, but the percentage of reticulated platelets increased significantly. Platelet aggregation and dense granular ATP secretion also increased significantly with ovariectomy. In platelet lysates, active MMP-2 increased, whereas MMP-14 significantly decreased, after ovariectomy; the expression of TIMP-1, TIMP-2, and P-selectin did not change. These results suggest that platelet turnover, aggregation, and ATP secretion increase with ovariectomy. Also, ovarian hormones selectively regulate the expression and activity of MMPs in porcine platelets. Increased platelet aggregation and activity of MMP-2 would alter platelet-platelet and platelet-vessel wall interactions, contributing to an exaggerated response to injury with loss of ovarian hormones.

Adenosine Triphosphate↗

PubMed2003

Human platelets contain estrogen receptor alpha, caveolin-1 and estrogen receptor associated proteins.

Venous thrombosis is a risk factor for oral estrogen treatment in men and women. Platelet responses mediated through estrogen receptors may be involved in these processes. However, expression of estrogen receptors and estrogen receptor-associated protein have not been defined clearly in human platelets. Therefore, the present study was designed to characterize estrogen receptors and estrogen receptor-associated proteins in human platelets. Platelets were obtained from normal female and male blood donors between the ages of 25 and 65 years. Estrogen receptors (ERalpha and ERbeta), heat shock proteins (hsp70 and hsp90), endothelial nitric oxide synthases (eNOS), caveolin-1, -2 and -3 and calmodulin were analyzed in total platelet lysate by immunoblotting. Expression of ERalpha and ERbeta, hsp70, hsp90, eNOS, calmodulin, and caveolin-1 were observed in both sexes. Expression of all proteins was similar in platelets from males and females. Results of the present study suggest for the first time that both estrogen receptors alpha and beta, caveolin-1 and other proteins associated with estrogen receptors and production of nitric oxide are present in platelets of both males and females.

Adult↗

PubMed2003

Species characterization of plasma nitrite/nitrate (NOx) concentration.

Experiments were designed to detect and determine differences between nitrite/nitrate concentration ([NOx]) in plasma across 15 species selected from seven classes of vertebrates. Blood collected in syringes was placed immediately into ethylenediaminetetraacetic acid (EDTA)-containing tubes and was centrifuged. Plasma [NOx] was determined by measurement of chemiluminescence. Across classes of vertebrates, baseline plasma [NOx] ranged from 0.6 to 171.3 nmol/ml. Mean +/- SD plasma [NOx] was highest in a fresh-water, jawless fish (lamprey, 95.5 +/- 9.1 nmol/ml) and lowest in a saltwater cartilaginous fish (skates, 1.1 +/- 0.4 nmol/ml). Both amphibians tested had a wide range in plasma [NOx], which was explained partly by temporal changes during the year. Within the mammalian class, plasma [NOx] ranged from 3.8 to 43.2 nmol/ml. Results of this study indicate that NO is detectable in plasma of all classes of vertebrates and that baseline concentration varies among species.

Animals↗

PubMed2002

Endothelial function in pigs transgenic for human complement regulating factor.

BACKGROUND: Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after xenotransplantation to nonhuman primates. Experiments were designed to characterize endothelial and smooth muscle function of arteries from pigs transgenic for hCD46. METHODS: Arterial blood from outbred pigs transgenic for hCD46 expression and nontransgenic animals of the same lineage was analyzed for angiotensin-converting enzyme (ACE), C-type natriuretic peptide (CNP), and nitric oxide. Aortic endothelial cells were prepared for measurement of mRNA or activity for nitric oxide synthase (NOS). Rings cut from femoral and pulmonary arteries were suspended in organ chambers for measurement of isometric tension. RESULTS: CNP was significantly greater, ACE was similar, and nitric oxide was significantly less in plasma from transgenic compared with nontransgenic pigs. Neither mRNA nor activity of NOS differed between the groups. Endothelium-dependent relaxations to bradykinin and acetylcholine but not the calcium ionophore were shifted significantly to the left in femoral and pulmonary arteries from hCD46 transgenic pigs compared with nontransgenic pigs. The ACE-inhibitor captopril augmented relaxations similarly in both groups, but NG-monomethyl-L-arginine (L-NMMA) did not inhibit relaxations in rings from transgenic pigs. CONCLUSIONS: Data suggest that expression of hCD46 on endothelium of pigs selectively augments endothelium-dependent relaxations to bradykinin by increased release of endothelium-derived factors other than nitric oxide. There does not seem to be any change in activity of ACE or NOS with expression of the human protein. Increased relaxations to bradykinin may be beneficial in lowering vascular resistance when transgenic organs are used for xenotransplantation.

Angiotensin I↗

PubMed2002

Endothelium-dependent effects of estrogen on vasomotor tone. Consequences of nongenomic actions.

Clinical observational and experimental studies indicate that estrogen has acute and prolonged effects on vascular function. Acute effects not requiring gene transcription or nongenomic responses include changes in intracellular calcium and activation of second messenger systems including release of endothelium-derived nitric oxide. However, interactions between rapid effects of estrogen and modulation of subsequent responses of endothelial cells are lacking. Experiments were designed to determine effects of estrogen on subsequent responses of endothelial cells to vasoactive stimuli. Human umbilical vein endothelial cells were cultured on coverslips and changes in intracellular calcium concentrations measured to 17 beta-estradiol and histamine. Estradiol alone did not increase intracellular calcium or modulate the peak calcium response to histamine. However, the decay of the peak calcium response to histamine was more rapid in the presence, compared to the absence, of estradiol. These results provide proof of principal that estradiol modulates responses of endothelial cells to vasoactive stimuli through changes in regulation of intracellular calcium.

Calcium↗

PubMed2002

Human leukocyte antigen class II immune response genes, female gender, and cigarette smoking as risk and modulating factors in abdominal aortic aneurysms.

OBJECTIVE: Aortic inflammation and the genes that regulate the immune response play an important role in abdominal aortic aneurysm pathogenesis. However, the modulating effects of such genetic and other environmental factors on the severity on aneurysm inflammation is not known. The objective of this study was to determine the influence of the human leukocyte antigen (HLA) class II genes, gender, and environmental factors on degree of abdominal aortic aneurysm tissue inflammation. METHODS: Aneurysm specimens were obtained at the time of operation from 96 consecutive patients who underwent abdominal aortic aneurysm repair and were graded for degree of histologic inflammation. Multivariate analysis was used to determine the association of genetic and environmental factors with degree of inflammation and to determine the HLA-associated disease risk for aneurysm. RESULTS: Active cigarette smoking and female gender were independently associated with high-grade tissue inflammation identified histologically (odds ratio [OR], confidence interval [CI]: 5.6, 1.6 to 19.3; and 6.0, 1.4 to 26.2, respectively), and a specific HLA allele (DR B1(*)01) was inversely associated with inflammation (OR, CI: 0.2, 0.04 to 0.7). Overall, the HLA-DR B1(*)02 and B1(*)04 alleles were significantly associated with disease risk, more than doubling risk for abdominal aortic aneurysm (OR, CI: 2.5, 1.4 to 4.3; and 2.1, 1.2 to 3.7, respectively). CONCLUSION: Active cigarette smoking and female gender are significant disease-modulating factors associated with increased abdominal aortic aneurysm inflammation. In addition, the HLA class II immune response genes possess both disease modulating and disease risk properties, which may be useful in early aneurysm detection and surveillance.

Aged↗

PubMed2002

Mechanism of raloxifene-induced relaxation in femoral veins depends on ovarian hormonal status.

Experiments were designed to study effects of raloxifene, a selective estrogen receptor modulator, on venous endothelium and smooth muscle. Rings of femoral veins with and without endothelium from adult gonadally intact, and ovariectomized female pigs were suspended for measurement of isometric force in organ chambers. Concentration-response curves to raloxifene (10-9-10-5 M) were obtained in rings at baseline tension or following contraction with prostaglandin (2 x 10-6 M) in the absence or presence of NG-monomethyl-l-arginine (l-NMMA) (nitric oxide synthase inhibitor), 1H-(1.2.4) oxadiazolo (4,3-A) quinoxalin-1-one (ODQ, soluble guanylate cyclase inhibitor), tetraethylammonium acetate (TEA; potassium channel blocker), or indomethacin (cyclooxygenase inhibitor). Raloxifene caused acute, concentration-dependent relaxations that were greater in rings with than in rings without endothelium from both groups. The l-NMMA significantly inhibited relaxations to raloxifene in rings with endothelium from ovariectomized females whereas TEA only inhibited relaxations in rings with endothelium from intact female pigs. ODQ and indomethacin significantly inhibited relaxations in rings with endothelium from both groups. These results suggest that raloxifene acutely relaxes femoral veins through release of endothelium-derived factors and by direct stimulation of vascular smooth muscle cells. Whether nitric oxide or potassium channel activation contributes to relaxations by raloxifene may depend on ovarian hormonal status of the animal.

Animals↗

PubMed2002

Ovariectomy upregulates expression of estrogen receptors, NOS, and HSPs in porcine platelets.

Platelets participate in normal and pathological thrombotic processes. Hormone replacement in postmenopausal women is associated with increase risk for thrombosis. However, little is known regarding how platelets are affected by hormonal status. Nitric oxide (NO) modulates platelet functions and is modulated by hormones. Therefore, the present study was designed to determine how loss of ovarian hormones changes expression of estrogen receptors and regulatory proteins for NO synthase (NOS) in platelets. Estrogen receptors (ER alpha and ER beta), NOS, heat shock proteins 70 and 90 (HSP70 and HSP90), caveolin-1, -2, and -3, calmodulin, NOS activity, and cGMP were analyzed in a lysate of platelets from gonadally intact and ovariectomized female pigs. Expression of ER beta and ER alpha receptors, endothelial NOS (eNOS), HSP70, and HSP90 increased with ovariectomy. NOS activity and cGMP also increased; calmodulin was unchanged. Caveolins were not detected. These results suggest that ovarian hormones influence expression of estrogen receptors and eNOS in platelets. Changes in estrogen receptors and NOS could affect platelet aggregation in response to hormone replacement.

Animals↗