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Biomedical subjects

M L Armstrong

Publications and source records attributed to M L Armstrong.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Fatty acid and lipid composition of the monkey retina in diet-induced hypercholesterolemia.

We determined the fatty acid composition of the lipids of cynomolgus monkey retina in animals fed commercial chow or a saturated fat, cholesterol-enriched atherogenic diet for 100 days. Doxosahexaenoic acid (22 : 6) accounted for 25.8% of the ethanolamine phosphoglyceride fatty acids, 17.6% of the serine plus inositol phosphoglyceride fatty acids, 8.4% of the choline phosphoglyceride fatty acids and 5.8% of the neutral lipid fatty acids in the retinas of the chow-fed animals. Therefore, monkey retinas, like those of other mammalian species, ordinarily contain large amounts of 22 : 6. Retinas from the monkeys fed the atherogenic diet contained less 22 : 6 as well as other polyunsaturates in each of the phospholipid classes. The decrease in polyunsaturates was compensated for by increases in palmitic, stearic, and oleic acids. There was no difference in the amount of phospholipid, the distribution of phospholipid classes, or the amount of cholesterol in the retinas of the monkeys fed the atherogenic diet. These results indicate that the single type of lipid alteration produced in the retina by a diet enriched in saturated fat and cholesterol is a decrease in the polyunsaturation of the retinal phospholipids. The reduction in retinal 22 : 6 content might have significance for photoreceptor function.

Animals↗
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Educating APNs for implementing the guidelines for adolescents in Bright futures: guidelines of health supervision of infants, children, and adolescents.

As the scope of what constitutes health and the range of determinants of health-promoting and compromising behaviors among adolescents are expanded, APNs must be well prepared to be powerful influences in the lives of all adolescents. The guidelines offered by Bright Futures challenge nurse educators to prepare APNs who possess the core competencies to knowledgeably address the health issues and concerns of all adolescents in multiple settings. The American Academy of Nursing Expert Panel's recommendations contained herein, if implemented, will further enhance the capabilities of graduate programs to prepare APNs to provide developmentally and culturally relevant disease prevention and health promotion care to adolescents and their families.

Adolescent↗
PubMedDate not supplied

Does baccalaureate nursing education for registered nurses foster professional reading?

Reading activities of registered nurses (RNs) were investigated using an untreated comparison group design study. The study group consisted of RN students (N = 60) enrolled in a baccalaureate in nursing (BSN) program at four distance education sites in northeast and central Texas who were queried about their reading activities. Total reading time of professional literature was reported at the time they started the nursing sequence of courses in their baccalaureate nursing program and 6 months after completion of these courses. The purposes of reading various types of professional literature also were identified by asking the respondent's interest, the perceived amount of application, and the commitment to reading this literature. RN counterparts at worksites of the RN-BSN students (N = 67) were respondents in the comparison group. After completing the BSN program, these nurses showed more interest in and commitment to reading and were more concerned about applying knowledge gained from reading in their nursing practice.

Adult↗
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Adolescent pregnancy, tattooing, and risk taking.

PURPOSE: To determine pregnant adolescents' interest in tattooing and identify additional risk-taking behaviors practiced by tattooed pregnant adolescents. DESIGN: A descriptive study with a convenience sample of 41 pregnant adolescents was conducted. The majority of participants were 16 to 17 years of age, 7 to 9 months gestation, single, in the 10th to 11th grades, and primarily White. A subgroup of five participants were tattooed. Participants completed the 71-item Armstrong Tattoo (AT) questionnaire. Descriptive statistics were used to describe the sample and evaluate responses. RESULTS: The majority of adolescents expressed interest in becoming tattooed; 48% expressed fear (disease, pain) as a deterrent to becoming tattooed. All tattooed participants had received tattoos prior to pregnancy. Decisions to become tattooed were made rapidly at 14 to 16 years of age, and all tattooed participants were impregnated by tattooed males. Most tattooed participants perceived themselves as risk takers, and all denied additional health problems (infection, blood-borne disease) related to the tattooing process. CLINICAL IMPLICATIONS: Proactive, preventive health education regarding maternal/fetal risks related to amateur and professional tattooing during pregnancy is needed. Pregnant adolescents aged 14 to 16 years who are dating a tattooed male may be at greater risk for impulsively deciding to become tattooed.

Adolescent↗
PubMedDate not supplied

Vascular responses to endothelin-1 in atherosclerotic primates.

Endothelin-1 (ET-1) is a vasoactive peptide that is released by endothelial cells. This study was performed to determine whether vascular responses to ET-1 are altered by atherosclerosis. ET-1 (1 or 10 nmol) was injected intra-arterially into the perfused hind limb of normal cynomolgus monkeys and monkeys fed an atherogenic diet for 19 months. We calculated the resistance of the total limb and large arteries and estimated the resistance of the small vessels. The major finding was that ET-1 had minimal effects on large arteries in normal monkeys but produced pronounced constriction of large arteries in atherosclerotic monkeys. In both groups, ET-1 produced dilatation of small vessels at 1 nmol and constriction at 10 nmol. Indomethacin (6 mg/kg intravenously) did not affect the responses to ET-1 in normal or atherosclerotic monkeys. In summary, the major finding is that the constrictor responses of large arteries to ET-1 are potentiated by atherosclerosis.

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Long-term cholesterol feeding alters the reactivity of primate coronary microvessels to platelet products.

Hypercholesterolemia impairs endothelium-dependent relaxations to several platelet-derived substances in large vessels. The effect of hypercholesterolemia on the response of coronary microvessels to platelet products and thrombin is less well defined. Three groups of cynomolgus monkeys were studied: normal (n = 6), short-term hypercholesterolemic (8-11 weeks, n = 5), and long-term hypercholesterolemic (18-80 months, n = 6). Responses of coronary microvessels, 100-200 microns in diameter, to thrombin (0.1-10 units/ml) and the platelet products ADP (1 nM-100 microM), serotonin (1 nM-100 microM), and the thromboxane A2 analogue U46619 were studied using an in vitro microvessel imaging apparatus. Vessels were studied after preconstriction with thromboxane A2 analogue U46619 to evaluate both relaxations and constrictions to each agent. Concentrations of U46619 to attain preconstriction were much lower for the long-term group (16 +/- 19 nM) as compared with the control and short-term hypercholesterolemic groups (689 +/- 48 and 664 +/- 63 nM, respectively, p less than 0.01). Relaxations of long-term hypercholesterolemic vessels to ADP tended to be less than those of either control or short-term hypercholesterolemic vessels. Thrombin, when added to normal or short-term hypercholesterolemic vessels, caused identical relaxations but paradoxically caused constrictions in microvessels of long-term hypercholesterolemic monkeys (55 +/- 17% of KCl contraction, p less than 0.001 vs. other groups). Peak constrictions to serotonin were markedly enhanced in the long-term hypercholesterolemic group (59 +/- 7% of maximal KCl responses) compared with control and short-term hypercholesterolemic responses (28 +/- 8% and 32 +/- 5%, respectively, both p less than 0.05 vs. long-term hypercholesterolemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
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Vascular responses to platelet activation in normal and atherosclerotic primates in vivo.

Platelets release vasoactive substances that may contribute to augmented vasoconstriction. In this study, we examined vascular responses to activation of platelets in vivo by infusion of collagen. Purified bovine collagen was infused into the blood-perfused hind limb of normal and atherosclerotic cynomolgus monkeys. Resistance of the total limb and large arteries was measured at constant flow. In normal monkeys, collagen produced a decrease in total limb resistance, with a modest constrictor response of the large arteries. In atherosclerotic monkeys, collagen produced a transient, small decrease in total limb resistance, with pronounced constriction of large arteries. Indomethacin (5 mg/kg i.v.) and the thromboxane A2/prostaglandin H2 receptor antagonist SQ29,548 (2 mg/kg i.v.) virtually abolished the large-artery constrictor response to collagen in atherosclerotic monkeys. The 5-HT2-serotonergic receptor antagonist ketanserin (0.6 mg/kg i.v.) had no effect on the vasoconstrictor response. We conclude that 1) large arteries constrict and small vessels dilate in response to collagen-mediated activation of platelets in vivo in normal and atherosclerotic monkeys, 2) large-artery constriction in response to activation of platelets is augmented in atherosclerotic monkeys, and 3) the augmented large-artery constriction in atherosclerotic monkeys may be mediated primarily by thromboxane. The findings provide evidence that platelets may contribute to augmented constrictor responses of atherosclerotic arteries.

Adenosine↗
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Structural and hemodynamic response of peripheral arteries of macaque monkeys to atherogenic diet.

The arteries of monkeys given atherogenic diets develop marked intimal thickening and medial thinning, but luminal size apparently changes minimally. The hemodynamic significance of the atherosclerotic changes is therefore uncertain. To evaluate vascular function in atherosclerotic arteries, we studied the hind-limb vessels of adult male rhesus and cynomolgus monkeys to assess the structural and hemodynamic responses to an atherogenic diet given for about 1.5 years or for much longer periods (6.5 years for rhesus and 4.3 years for cynomolgus monkeys). The intimal cross-sectional area greatly increased after the atherogenic diet, but there was no significant luminal narrowing after either the 1.5-year diet or the longer diet periods. The media of atherosclerotic arteries showed focal atrophy and focal thinning after pressure fixation, but the total medial mass was not decreased even after the long diet periods. Hemodynamic studies indicated mild functional impairment in the atherosclerotic vessels; resting resistance increased and vasodilator responses decreased, but adrenergic responses were preserved. Thus, the marked changes that occur in the arterial wall in experimental primate atherosclerosis include adaptations to lesion formation that permit a long prestenotic phase of atherosclerosis in which vascular dysfunction is minimal.

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Blood flow through vasa vasorum of coronary arteries in atherosclerotic monkeys.

Morphologic studies and postmortem arteriograms provide qualitative evidence that atherosclerosis induces neovascularization in coronary arteries. In this study we obtained the first measurements of blood flow through vasa vasorum in atherosclerotic coronary arteries. We measured blood flow with microspheres to intima media and to adventitia in normal and atherosclerotic cynomolgus monkeys. Blood flow to adventitia was not altered by atherosclerosis. The blood flow to intima media, however, was increased more than fivefold by atherosclerosis: flow was 3 +/- 1 in normal animals and 16 +/- 5 in atherosclerotic monkeys (p less than 0.05). Blood flow was threefold greater in atherosclerotic than in normal coronary arteries during adenosine-induced vasodilatation, which suggests that proliferation of new vessels, not dilatation of existing vessels, accounts for the increase in flow through vasa in intima media. Histologic studies indicated that vasa vasorum to intima media in atherosclerotic coronary arteries originate from adventitial vasa. We conclude that: 1) there is a large increase in blood flow through vasa vasorum to intima media, but not to adventitia, in atherosclerotic coronary arteries; and 2) increased flow is produced primarily by proliferation of new vessels that originate from adventitial vasa.

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Cerebral vasoconstrictor responses to serotonin after dietary treatment of atherosclerosis: implications for transient ischemic attacks.

Serotonin, which is released when platelets aggregate at carotid lesions, may contribute to cerebral ischemia. Our goal was to test the hypothesis that dietary treatment of atherosclerosis reverses the augmented cerebral vasoconstrictor response to serotonin. We studied normal cynomolgus monkeys, atherosclerotic monkeys, and atherosclerotic monkeys that were fed a normal (regression) diet for 18 months. Morphometric studies indicated that the regression diet reduced intimal area in the carotid arteries by about 50-75%. Cerebral blood flow was measured with microspheres, and microvascular pressure was measured with a micropipette in pial arteries that were approximately 300 micron in diameter. Values for cerebral blood flow and arteriolar pressure were used to calculate resistance of large cerebral arteries (greater than 300 micron diameter). Infusion of serotonin produced a modest increase in the resistance of large cerebral arteries in normal monkeys. Vasoconstrictor responses to serotonin were increased more than fivefold in atherosclerotic monkeys. The major finding of the study is that dietary treatment of atherosclerosis abolishes augmented cerebral responses to serotonin.

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PubMedDate not supplied

Perhexiline maleate in the treatment of angina pectoris in patients awaiting coronary artery bypass surgery.

Twenty-five patients with angina pectoris due to coronary artery disease who had not responded to other medical therapy and on the waiting list for coronary bypass surgery were treated over a period of 4 weeks with perhexiline maleate (100 mg to 400 mg/day) in addition to their other therapy. There was an 80% reduction in the average number of both anginal attacks and nitroglycerin requirement when the pre-treatment week and the 4th week of perhexiline maleate therapy were compared (p less than 0.0001). Six of the patients had no anginal attacks at all and did not require sublingual nitro glycerin tablets during the 4th week of perhexiline maleate therapy.

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