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Biomedical subjects

A Antonopoulos

Publications and source records attributed to A Antonopoulos.

At least 19 recordsLinked to original sources
PubMed2004

Characterisation of iota-carrageenans oligosaccharides with high-performance liquid chromatography coupled with evaporative light scattering detection.

Enzymatically digested oligo-iota-carrageenans were separated with liquid chromatography, coupled to evaporative light scattering detection. As expected, compared to oligo-kappa-carrageenans, the additional sulphate group in the neocarrabiose unit of iota-carrageenans significantly modified the separation mechanisms on ion-exchange chromatography, porous graphitic carbon and ion-pair chromatography. The oligomers were then isolated and characterised off-line with electrospray ionisation mass spectrometry in positive-ion mode. The tetrasaccharide, hexasaccharide and octasaccharide that were identified were associated with protonated heptylamine molecules whose number depended on the number of sulphate groups.

Anion Exchange Resins↗
PubMed2004

Comparative analysis of enzymatically digested kappa-carrageenans, using liquid chromatography on ion-exchange and porous graphitic carbon columns coupled to an evaporative light scattering detector.

Enzymatically digested kappa (A-G4S)-carrageenans, apart from their biological activities in plants, could be used as 'model' molecules to elucidate potential problems in nuclear magnetic resonance spectroscopy of carrageenans. Thus, oligosaccharides obtained from kappa-carrageenan by enzymatic digestion using kappa-carrageenase have been separated on silica and polymeric based ion-exchange and porous graphitic carbon (PGC) columns, coupled to an evaporative light scattering detector. Oligomers were separated on ion-exchange columns using a gradient of ammonium acetate as a developing ion, while analysis on PGC column presented an additional adjacent peak next to each main one, using a gradient of ammonium acetate in water/acetonitrile as a mobile phase. The phenomenon can be attributed to different retention mechanisms that govern the PGC surface. Furthermore, it has been demonstrated that acetonitrile can regulate the selectivity between the peaks raising hopes for preparative chromatography.

Carrageenan↗
PubMed2003

Study of the attachment of Na+ on glucose and on some of its methylated derivatives.

The mechanism of attachment of Na(+) on glucose, methyl-alpha-D-glucose, methyl-beta-D-glucose, 3-O-methylglucose, tetra-O-methylglucose, and also on galactose and methyl-beta-D-galactose, was studied. For this we measured the ion yields for the complex [sugar-Na(+)] formed by ionisation by matrix-assisted laser desorption/ionisation (MALDI) and ionspray. These data were compared with the relative volatilities and hydrophobicities of the sugars, measured by evaporative light scattering and reversed-phase liquid chromatography, respectively. Some formation enthalpies for the complexes [sugar-Na(+)], starting from the sugar and the cation, were obtained by ab initio calculations. No simple correlations could be observed between the ion yields and the parameters studied, so that the cationisation mechanism of the sugars remains unclear.

Glucose↗
PubMed2002

Experience with predeposition of autologous blood in elective orthopaedic and plastic surgery: the role of oral iron medication.

The risk of transmission of transfusion-associated infections, mainly AIDS, led to the increased use of autologous transfusion by four methods: predeposition of autologous blood, haemodilution, intraoperative and postoperative blood salvage. We started a program of autologous predeposition at blood transfusion centre of Saint Andrews General Hospital of Patras in co-operation with orthopaedic and plastic surgery in 1992. To date, 617 autologous units have been collected from 257 patients undergoing various operations. Our protocol was as follows: the minimum Hb value before each donation was 12 g/dl, body weight over 50 kg, age 18-70 years and 8-10 day intervals between donations. The exclusion criteria were anaemia, evidence of blood loss, renal disease, chronic and acute inflammatory or malignant disorders, pregnancy and lactation. We chose 40 patients with haemoglobin values of 13-15 g/dl and ferritin levels > 50 ng/ml, who gave three autologous units. They were separated in two groups of twenty patients. Those in group 1 received 300 mg of elemental iron in three daily oral doses, while the others in group 2 received no iron medication. We studied haematologic variables, reticulocytes and ferritin levels in both groups before each autologous donation. We also studied the possible complications and their incidence in patients over 60 years old. According to our results, haematologic variables such as Hb, mean corpuscular Hb (MCH), mean corpuscular volume (MCV) and reticulocytes were not influenced by oral iron therapy. We observed a slight increase in MCV in both study groups which means the production of larger red blood cells. We also noticed a higher decrease of ferritin in patients with no iron therapy, but without a fall of ferritin levels under the normal values. We conclude that oral iron therapy in non-iron deficient patients undergoing a moderate program of three autologous units is not necessary. In addition, autologous blood donation is also feasible in patients over 60 years old without severe complications.

Adolescent↗
PubMed1998

Early postexercise thallium-201 reinjection after sublingual nitroglycerin augmentation: effects on detection of myocardial ischemia and/or viability.

BACKGROUND: Thallium-201 (201Tl) reinjection after conventional redistribution imaging is a standard procedure, resulting in enhanced 201Tl redistribution which is compatible with viable myocardium. Although this method significantly improves identification of viable myocardium, it increases the investigation time by approximately 1 h. Thus, this technique is suboptimal from the standpoint of patient convenience, since its routine performance may be impractical in a high-volume nuclear medicine laboratory. HYPOTHESIS: This study was undertaken to evaluate the efficacy of an early 201Tl reinjection and imaging protocol in combination with sublingual nitroglycerin, to detect myocardial ischemia and/or viability, and to reduce the need for conventional (4 h) redistribution imaging. MATERIALS AND METHODS: In this study, 62 consecutive coronary patients, referred for the detection of possible myocardial ischemia and/or viability, were involved (mean age 55 years, range 41-70). Of those, 50 had previous angina attacks, with 42 having a history of previous myocardial infarction; 10 patients had coronary artery bypass grafting; and the remaining 2 had atypical chest pain. Immediately after the completion of the initial postexer-cise imaging, 0.3 mg sublingual nitroglycerin followed by the reinjection of 1 m Ci of 201Tl were administered, and two further sets of images were acquired 1 h and 4 h later. RESULTS: In each set of images, a total of 496 segments were analyzed. On postexercise imaging, 305 (61%) segments demonstrated defects of which 198 (65%) showed enhanced thallium uptake, 97 (32%) did not change, and 10 (3%) showed reverse redistribution on 1 h reinjection imaging (IRI). Of the 97 persistent defects, only 17 (6%) showed fill-in of 201Tl on 4 h redistribution imaging (CRI), while 12 (4%) segments showed reverse redistribution. On the other hand, after analyzing the 62 patients of the 1 h IRI, 17 (27%) remained unchanged while in only 1 patient (6%) of 17 the diagnosis changed from myocardial necrosis to ischemia after analysis of the 4 h CRI. CONCLUSION: These results indicate that early postexercise reinjection of 201Tl in combination with sublingual nitroglycerin followed by 1 h image acquisition may prove useful for a comprehensive and convenient assessment of myocardial ischemia and/or viability.

Adult↗
PubMed1998

Thallium-201 for detection of myocardial viability: comparison of early postexercise reinjection and imaging with 4 and 18-24 hours redistribution imaging.

To evaluate the efficacy of an early 201Tl reinjection and imaging protocol for reducing the need for conventional 4-hour or optimal 24-hour redistribution imaging (RI) and detecting of myocardial viability, we compared the results of early postexercise Tl reinjection and imaging with those of 4- and 24-hour RI in 74 consecutive patients aged 55 +/- 9 years (mean +/- SD) who were assessed for myocardial ischemia. One millicurie of Tl was injected promptly after completion of the initial postexercise imaging (PEX) and three additional sets of images were acquired 1, 4 and 18-24 h later. A total of 2,368 segments were evaluated. On PEX, 390 (17%) segments showed defects, of which 287 (74%) showed enhanced Tl uptake at 1-hour RI; 89 (23%) did not change and 14 (4%) showed reverse redistribution. Of the 103 persistent defects, only 27 (7%) showed further fill-in of Tl; 62 (16%) segments showed reverse redistribution at 4-hour RI while at 18- to 24-hour RI 17 (4%) and 47 (12%) segments showed further fill-in of Tl and reverse redistribution, respectively. Finally, after analysis of 4- and 18- to 24-hour RI, the diagnosis changed from myocardial necrosis to ischemia in only 2 (3%) patients. In conclusion, these results suggest that by eliminating the need for an additional delayed set of images for detection of myocardial viability, this protocol reduces the total investigation procedure, is more convenient for the patient, increases patient turnover and expedites the decision-making process.

Decision Making↗
PubMed1996

Captopril adjuvant therapy to beta-blockers and nitrates improves post-myocardial infarction left ventricular performance.

A growing body of data support the beneficial effects of angiotensin-converting enzyme inhibitors in the prevention of cardiac enlargement and improvement of left ventricular function in patients with acute myocardial infarction. However, very little information exists about the direct effect of increased afterload on cardiac performance in these patients and the possible favourable effects of angiotensin-converting enzyme inhibitors as adjunctive treatment to thrombolysis, beta-blockers and nitrates. We have, therefore, studied the effects of captopril as adjuvant therapy to thrombolysis, beta-blockers and nitrates (standard therapy) on left ventricular performance in 77 consecutive patients with uncomplicated Q-wave acute myocardial infarction, by the measurement of the pre-ejection period/left ventricular ejection time ratio before and after (0.25-0.50 mg) phenylephrine administration on the 4th and 30th post-infarction days. Patients were randomized on day 4 either to continue standard therapy alone (group 1, 35 patients) or to receive oral captopril therapy (12.5 mg t.i.d.) in addition to standard therapy (group 2, 42 patients) in a double-blind parallel study. Among the patients of group 1 there was a significant deterioration of left ventricular function after phenylephrine administration. This was shown by an increase of pre-ejection period/left ventricular ejection time ratio only in the subset of patients with ejection fraction < 40%, as measured by contrast ventriculography, on both the 4th and 30th post-infarction days changing from 0.435 +/- 0.070 to 0.528 +/- 0.101, P < 0.01 and from 0.404 +/- 0.098 to 0.515 +/- 0.092, P < 0.02, respectively. In contrast there were no significant changes in patients with ejection fraction > or = 40%. Among patients of group 2, phenylephrine administration induced a significant increase, only on the 4th day, in pre-ejection period/left ventricular ejection time ratio only in the subset of patients with ejection fraction < 40% changing from 0.410 +/- 0.107 to 0.535 +/- 0.102, P < 0.01. In the remaining patients with ejection fraction > or = 40% there were no significant changes on either the 4th or 30th post-infarction days. Furthermore, a significant improvement was observed after phenylephrine administration in the pre-ejection period/left ventricular ejection time ratio between the 4th and 30th post-infarction days, which changed from 0.535 +/- 0.102 on day 4 to 0.368 +/- 0.052 on day 30 (P < 0.004). Also, a four-way ANOVA detected a significant reduction of heart rate in patients with ejection fraction < 40% from day 4 to day 30. The results indicate that: (1) the response of pre-ejection period/left ventricular ejection time ratio after increasing afterload may be a useful non-invasive method for the detection of left ventricular dysfunction in myocardial infarction patients; and (2) captopril adjuvant therapy as compared to thrombolysis, beta-blockers and nitrates alone, after phenylephrine administration, improves the left ventricular performance response in asymptomatic Q-wave post-infarction patients and beneficially affects heart rate. This effect is most pronounced in patients with ejection fraction < 40% whereas those with ejection fraction > or = 40% do not obtain clear benefit.

Adrenergic beta-Antagonists↗
PubMed1995

Cytological effects of 50 Hz electromagnetic fields on human lymphocytes in vitro.

Incubation of human peripheral blood cultures in the presence of an electromagnetic field (EMF) of 50 Hz and 5 mT leads to stimulation of the cell cycle of dividing lymphocytes but has no influence on the frequencies of sister-chromatid exchanges. Comparative studies with two different exposure systems and with different culture temperatures indicate that the effect on the cell cycle results from the EMF and is not a thermal effect. These data support the assumption that with respect to their suspected carcinogenic effects EMFs have no initiating but probably promoting effects.

Carcinogens↗
PubMed1995

Sex differences in the anatomy of coronary artery disease.

In a prospective study, the extent and severity of coronary artery disease (CAD) as well as the location of coronary stenoses were studied comparatively, in relation to age and sex, in 192 consecutive women vs 543 selected men, who all underwent coronary angiography during the same time period, and who were found to have significant CAD. Overall, the age of women (59 +/- 8 years) was higher than that of men (55 +/- 8 years), p < 0.001. Also, the prevalence of smoking was higher in men (81% vs 31%, p = 0.0000) and that of diabetes mellitus in women (29% vs 12%, p = 4 x 10(-6)). In addition, women over 50 years old had a higher incidence of hypertension (51% vs 32%, p = 6 x 10(-5)). Although in both sexes the prevalence of multivessel CAD increased with age, the prevalence of one-vessel CAD was significantly more and that of three-vessel CAD significantly less common in women than in men, both overall (35% vs 16%, p = 4 x 10(-8) and 36% vs 54%, p = 2 x 10(-5), respectively) and in all age subgroups. However, the location of coronary stenoses did not show important differences between men and women with the left anterior descending being the most frequently involved artery. Furthermore, the calculated Gensini index, which reflects cumulatively the extent, severity and location of coronary stenoses, was significantly higher in men (59.2 +/- 34.6 vs 52.2 +/- 36.2, p = 0.03), implying more severe and extensive CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Systolic time intervals after phenylephrine administration for early stratification of patients after acute myocardial infarction.

This study was designed to assess the usefulness of the changes in left ventricular (LV) systolic time intervals after phenylephrine administration for detecting high-risk patients soon after acute myocardial infarction by correlation with the angiographic and ventriculographic findings. The procedure was performed in 76 consecutive patients (group I) on the fourth postinfarction day and in 12 normal subjects (group II) free of coronary artery disease. In 20 patients with LV ejection fraction < or = 40% (subgroup IA) the preejection period (PEP)/LV ejection time (ET) ratio increased from 0.410 +/- 0.107 to 0.535 +/- 0.102 (p = 0.01) after phenylephrine, whereas in the remaining 56 patients (subgroup IB) with LV ejection fraction > 40% and in the 12 normal subjects the PEP/LVET increased nonsignificantly. Of patients with LV ejection fraction > 40% a subset of 20 patients was distinguished with proximal stenosis in both left anterior descending and either a dominant right or left circumflex coronary artery (subset IB-a). In these the PEP/LVET increased from 0.347 +/- 0.056 to 0.445 +/- 0.019 (p = 0.0001) after phenylephrine, whereas in the remaining 36 patients (subset IB-b) without proximal lesions in 2 main arteries the PEP/LVET increased nonsignificantly. In conclusion, the PEP/LVET response to phenylephrine administration early after acute myocardial infarction is a precise, safe, noninvasive bedside method for early stratification of these patients.

Adult↗
PubMed1993

Early ventricular fibrillation in patients with acute myocardial infarction: correlation with coronary angiographic findings.

To define coronary angiographic characteristics of patients experiencing early primary ventricular fibrillation (VF) in the acute phase of myocardial infarction we studied 266 consecutive patients without clinical evidence of heart failure. Twenty-six patients (group 1) experienced early (< 12 h from the onset of symptoms of myocardial infarction) primary VF whereas 240 patients (group 2) with the same clinical characteristics served as an appropriately matched cohort. All patients were catheterized before or soon after hospital discharge (1 to 8 weeks after the acute event). There was no significant difference in left ventricular ejection fraction between the two groups of patients (39.6 +/- 6% vs 36.9 +/- 8%, P = ns). Patients with early VF had a significantly greater number of diseased vessels than those without VF (3.38 +/- 1.05 vs 2.03 +/- 1.25, P < 0.001) and a higher coronary arteriographic Gensini score (29.31 +/- 4.80 vs 20.16 +/- 4.14, P < 0.001). The left anterior descending coronary artery was identified as the infarct-related vessel in 53.6% of group 1 vs 44.5% of group 2 patients (P < 0.05). The mean maximal serum creatine kinase values were not significantly different (1897 +/- 1062 vs 1426 +/- 839 IU.l-1, P = ns) between the two groups. These data indicate that patients with early primary VF in the setting of acute myocardial infarction may have more extensive coronary artery disease than similar patients without VF. A worse prognosis could be anticipated for these patients on the basis of worse coronary anatomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Plasma atrial natriuretic factor in uncomplicated acute myocardial infarction.

Plasma atrial natriuretic factor (ANF) levels were measured in 29 patients who had normal atrial hemodynamics on days 4 and 8 after an uncomplicated acute myocardial infarction (AMI). All patients had increased ANF levels on day 4. On day 8 of the ANF levels had declined significantly to normal values in 14 patients with enzymatically smaller AMI and higher ejection fractions (> or = 40%), while they remained elevated in 16 patients with larger AMI and lower ejection fractions (< 40%). The study data are compatible with increased secretion of ANF by the more extensively damaged left ventricles in AMI.

Adult↗
PubMed1993

Angina and coronary artery disease in patients with aortic valve disease.

The significance of angina pectoris in patients with aortic valve disease (AVD) and the need for coronary arteriography before valve replacement are controversial. The history of chest pain and coronary arteriographic findings were reviewed in 333 patients > or = forty years old, with AVD: 142 with aortic stenosis, 87 with mixed AVD and 104 with aortic regurgitation. The prevalence of coronary artery disease (CAD) was similar among different types of AVD. Angina pectoris was more frequent in patients with aortic stenosis (56%) and mixed AVD (53%) than in patients with aortic regurgitation (24%) (p < 0.0001). Similar results were found in patients with and without CAD. Twenty-six of 95 (27%) patients with CAD had no chest pain at all. The absence of any chest pain in CAD patients was more frequent in those > or = sixty years old than in those < sixty (p < 0.05). Thus, since a significant number of patients had CAD in the absence of any chest pain, the authors recommend coronary arteriography for all patients > or = forty years of age before aortic valve replacement.

Aged↗
PubMed1992

Correlation of reciprocal ST-segment depression after acute myocardial infarction with coronary angiographic findings.

We studied 266 consecutive patients with acute myocardial infarction to assess the significance of electrocardiographic "mirror images". Ninety-four (group A) had anterior wall and 132 (group B) had inferior wall infarction. Thirty-one group A patients had stenosis of the right coronary artery greater than 85% in diameter (subgroup A1), and 63 either had a normal right coronary artery or less than 85% stenosis (subgroup A2). Of group B patients 62 had greater than 85% stenosis of the left anterior descending (subgroup B1) and 70 had a left anterior descending or less than 85% stenosis (subgroup B2). ST-segment depression was significantly greater in depth and duration in subgroup A1 than A2 (p = 0.02) and in subgroup B1 than B2 (p = 0.02, p = 0.01, respectively). Left ventricular ejection fraction was lower in subgroup A1 than A2 (p less than 0.001) and in B1 than B2 (p less than 0.001). There was a strongly positive correlation between depth and duration of ST-segment depression and the Gensini index (r = 0.78, 0.84) for anterior and inferior infarction, respectively. In conclusion, increased depth and duration of ST-segment depression opposite the infarct are indicative of ischemia, and are related to the extent of coronary artery disease, the degree of stenosis of the vessels supplying the opposite wall and of left ventricular dysfunction.

Aged↗
PubMed1992

Early atrial arrhythmias in acute myocardial infarction. Role of the sinus node artery.

We studied atrial arrhythmias during the first 12 h of admission to the hospital in 266 consecutive patients with acute myocardial infarction who subsequently underwent coronary angiography. Ten patients developed atrial fibrillation, one atrial flutter, and one supraventricular tachycardia. Another five developed sinus dysrhythmias. All of the above patients had an acute inferior myocardial infarction, and in 10 of the 12 patients with supraventricular arrhythmias and in four of five with sinus dysrhythmias, the origin of the sinus node artery started just after an occluded right coronary or left circumflex artery or was involved in the occlusion. Thus, ischemia of the sinus node due to coronary occlusion proximal to the origin of the sinus node artery was a likely cause of these arrhythmias.

Adult↗
PubMed1990

Multimodal biochemical modulation of 5-fluorouracil activity in advanced colorectal cancer with allopurinol, folinic acid and dipyridamol.

It is now commonly accepted that the activity of 5-fluorouracil (5FU) may be potentiated by folinic acid (FA). Moreover dipyridamol (DIP) interacts with the pyrimidine salvage pathway of 5FU. In 28 patients with advanced colorectal cancer, in progression under FA-5FU, we continued treatment with FA-5FU plus DIP. FA 200 mg/m2/day. i.v. push was given before 5FU 766.52 mg/m2/day (mean dose), in 60 min infusion for 5 subsequent days. Cycle was repeated every 21 days. We noticed greater but not seriously increased toxicity by the addition of DIP. The addition of DIP did not change response rates; it seemed to increase response but not significantly.

Allopurinol↗