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A Maes

Publications and source records attributed to A Maes.

At least 73 records · Page 4Linked to original sources
PubMed1998

Nuclear cardiology, Part II: Scintigraphic evaluation of cardiac function.

OBJECTIVE: Different methods are currently available to assess cardiac function, especially left ventricular ejection fraction, using either planar or tomographic imaging, first-pass or equilibrium techniques, and blood-pool or myocardial perfusion agents. This is the second article of a four-part series on nuclear cardiology. In this article the authors review the most widely used radiopharmaceuticals and methodologies.

Coronary Circulation↗
PubMed1998

Nuclear cardiology, Part III: Scintigraphic evaluation of cardiac perfusion.

OBJECTIVE: After reading Part III of this series of nuclear cardiology articles, the technologist should be able to: (a) compare and contrast radiopharmaceuticals used for myocardial perfusion imaging; (b) describe imaging protocols used for detecting coronary artery disease; and (c) describe imaging patterns seen following reconstruction of myocardial images.

Coronary Circulation↗
PubMed1997

Cytogenetic effects of 935.2-MHz (GSM) microwaves alone and in combination with mitomycin C.

This paper focuses on the genetic effects of microwaves from mobile communication frequencies (935.2 MHz) alone and in combination with a chemical DNA-damaging agent (mitomycin C). Three cytogenetic endpoints were investigated after in vitro exposure of human whole blood cells. These endpoints were the 'classical' chromosome aberration test, the sister chromatid exchange test and the alkaline comet assay. No direct cytogenetic effect was found. The combined exposure of the cells to the radiofrequency fields followed by their cultivation in the presence of mitomycin C revealed a very weak effect when compared to cells exposed to mitomycin C alone.

Chromosome Aberrations↗
PubMed1997

PET scan predicts recovery of left ventricular function after coronary artery bypass operation.

BACKGROUND: Viable but hypocontractile myocardium can show functional improvement after revascularization (hibernation). It is sometimes difficult, however, to predict viability and recovery in patients with severe left ventricular function. This study sought to identify possible predictive factors of recovery of cardiac function after revascularization in patients with three-vessel disease. METHODS: Positron emission tomography (fluoro-18-deoxyglucose uptake for metabolism; nitrogen 13-labeled ammonia for flow) and equilibrium-gated nuclear angiography (for the global ejection fraction) were performed in 59 patients with three-vessel disease before and after undergoing coronary artery bypass grafting. The positron emission tomographic data were expressed as match normal (flow and metabolism normal), mismatch (low flow, high metabolism), match viable (moderate decrease in flow and metabolism), and match necrosis (low flow and metabolism). RESULTS: Stepwise logistic regression analysis showed that only mismatch regions played a significant role in predicting postoperative improvement in function (p = 0.019). There were 1.7 +/- 1.5 mismatch regions in 31 patients who showed an improvement in their ejection fraction (0.47 +/- 0.14 versus 0.58 +/- 0.11; mean +/- standard deviation) versus 0.8 +/- 1.0 mismatch regions (p = 0.017) in patients who did not show recovery. There was more pronounced functional improvement with increasing numbers of mismatch regions, and patients with at least one mismatch region had a high likelihood of recovery (p < 0.001). In patients with a very low preoperative ejection fraction and two or more mismatch regions, there was early significant recovery (0.27 +/- 0.08 versus 0.46 +/- 0.06; p = 0.009). CONCLUSIONS: At least one mismatch region must be present for there to be a postoperative functional benefit. When a low left ventricular ejection fraction is associated with mismatch, early recovery is substantial.

Adult↗
PubMed1997

Importance of flow/metabolism studies in predicting late recovery of function following reperfusion in patients with acute myocardial infarction.

AIMS: Positron emission tomographic imaging is known to be a reliable indicator of viable myocardium in chronic heart disease. Its value in acute myocardial infarction has not been studied extensively. METHODS AND RESULTS: Sixty-two patients receiving thrombolytic therapy were studied. Myocardial tissue flow and metabolism were measured at 5 days and 3 months. Recovery of left ventricular function was investigated with echocardiography or radionuclide ventriculography. In eight patients, normal flow was found in the infarct area at 5 days with no significant changes in flow, metabolism or function over the next 3 months. In 54 patients, impaired regional myocardial blood flow in the infarct zone was observed at 5 days. In 39 patients, there was a matching positron emission tomographic pattern, while in 15 the pattern was mismatched. None of the patients with a TIMI flow grade < 3 revealed recovery of left ventricular function. In seven out of 11 patients with TIMI 3 flow and a mismatching pattern, additional angioplasty was performed with functional improvement in six. CONCLUSIONS: Recovery of ventricular function is exclusively found in patients with a TIMI flow grade 3. Patients with a positron emission tomographic mismatching pattern reveal functional recovery only after subsequent angioplasty.

Aged↗
PubMed1997

Prognostic significance of nm23 protein expression in malignant melanoma. An immunohistochemical study.

The NM23 genes, encoding for the red blood cell nucleoside diphosphate kinases A and B, have been found to serve as metastasis-suppressor genes in experimental animal models of tumour progression, and in some, but not all cancers in man. To investigate the role of NM23 in the progression of human malignant melanoma, we studied the expression and distribution of the nm23 protein with a sensitive immunohistochemical technique and a well-characterized monoclonal antibody in 41 benign pigment cell lesions and 71 uniformly treated malignant melanomas with a long follow up-up. In benign naevi, the junctional nests frequently expressed nm23 protein, whereas the immunoreactivity tended to decrease when the lesions matured. All malignant melanomas expressed nm23 protein in their vertical and/or radial growth phases, and the immunoreactivity tended to increase towards the deeper parts of the lesion. No relation was found between nm23 expression and patient outcome. In addition, nm23 was found in activated lymphoid cells, and this feature was significantly associated with a brisk lymphocytic stroma response in malignant melanomas. Our data are at variance with previous mRNA studies on malignant melanoma, and indicate that routine immunohistochemical analysis for nm23 protein on paraffin-embedded tumour tissue cannot reliably be used as a prognostic marker for patients suffering from malignant melanoma. In contrast, our findings suggest that the nm23 protein in pigment cell lesions is related to the proliferative or activated state of pigment cells, rather than to their metastatic potential.

Adult↗
PubMed1997

The cell cycle positions influence DNA migration as measured with the alkaline comet assay in stimulated human lymphocytes.

Virtually any eukaryotic cell can be processed for analysis of DNA damage using the comet assay. The most commonly examined human cells are lymphocyte populations. However, many parameters can affect the response of lymphocytes to the assay in terms of the ability to detect damage. The response of cultivated lymphocytes in the comet assay indicated cycle-dependent differences. The cell cycle position has been shown to affect the results obtained using both the alkaline and neutral assays. This is primarily a reflection of the complications of including S-phase DNA. In the alkaline assay, replicating structures are interpreted as strand breaks when denatured, increasing the level of detectable damage. We performed the alkaline comet assay to detect differences in the extent of DNA in stimulated human lymphocytes collected at different sample times after mitogen stimulation. Our results clearly indicate that proliferating lymphocytes have a greater migration of DNA (measured with the comet assay as DNA damage) than quiescent lymphocytes. The lymphocytes collected at 36, 42, and 48 h after mitogen stimulation showed a significantly increased extent of DNA migration in comparison to the lymphocytes collected at 0 and 24 h after stimulation. It, probably, can be explained by the higher frequency of the S phase cells in lymphocyte populations collected at 36, 42, and 48 h. Sites of active DNA replication during the S phase behave like single-strand breaks when denatured in alkali, and their presence may result in a significant increase of the tail moments in S phase cells.

Adult↗
PubMed1997

[Hibernating myocardium and the 'no reflow' phenomenon: a study of absolute regional myocardial perfusion and glucose metabolism using positron emission tomography in chronic and acute heart disorders].

Positron emission tomography (PET) is a powerful tool for in vivo measurements of physiologic processes such as regional myocardial blood flow and metabolism. Myocardial blood flow is often studied using radioactive labeled ammonia (13NH3) while myocardial metabolism can be investigated using 18F-fluorodeoxyglucose (FDG). Moreover, the use of appropriate kinetic models allows quantification of these processes. In this study, myocardial viability in both chronic and acute heart disease was investigated by the use of positron emission tomography. In this context, viable refers to dysfunctioning areas of the myocardium in which functional recovery is observed after revascularization. In patients suffering chronic coronary artery disease, PET findings of flow and metabolism were correlated with myocardial ultrastructure. In dysfunctional myocardial segments, normal 13NH3 uptake or decreased 13NH3 uptake with relatively increased FDG uptake (PET mismatch) indicates the possibility for functional recovery after bypass surgery. Since absence of scar tissue in these segments is likely to be required for functional recovery, it was not surprising that little fibrosis was found in myocardial biopsies taken in PET mismatch areas. The biopsies also revealed the presence of viable myocardial cells showing a variable loss of contractile material. The contractile material was replaced by glycogen. One could wonder about the time course needed for functional recovery after restoration of blood flow in the presence of a considerable amount of cells lacking a normal contractile apparatus. It would therefore be interesting to study functional recovery at different time points in patients with variable amounts of these myolytic cells. Probably, recovery of contractility would be slower in myocardial areas with a larger amount of abnormal cells. Another question that arises is the meaning of the increased FDG signal in dysfunctional, though viable myocardium. At first sight, glycogen storage in myolytic cells seems an excellent candidate to explain the increased intake of FDG in PET mismatch areas. However, in this study, in areas considered nonviable by PET, similar amounts of myolytic cells were found. Histologically altered cells might represent a structural and protective adaptation to long term hypoperfusion or to repetitive episodes of ischemia. Another possibility for the increased FDG uptake is an enhancement of glucose utilization in the mismatch areas not only in the myolytic cells, but also in the morphologically normal cell fractions. In patients with a PET mismatch pattern, significant recovery of flow and function was observed after surgery with a significant decrease in glucose utilization. Although it would have been interesting to histologically study the fate of myolytic cells in these recovered areas, this was not possible for obvious ethical reasons. In areas considered non viable by PET expressing a concordant decrease of 13NH3 and FDG uptake (PET match), no recovery of function, flow or metabolism was noted at follow-up. Another study was conducted in our department in infarct patients in which regional myocardial blood was measured within 24 hours after successful thrombolysis. The aim was to investigate the presence of impaired tissue perfusion in the acute stage and to evaluate its effect on recovery of flow, metabolism and function. In about 30% of patients with a TIMI 3 patent vessel, seriously impaired tissue flow was observed in the acute stage. Whether this impairment was due to irreversible damage to capillaries or myocytes, to reperfusion injury or to the presence of multiple distal thrombi remains unknown. Most patients showing severely impaired regional myocardial blood flow in the acute stage revealed absence of viable myocardium on follow-up PET NH3/FDG scans.

Acute Disease↗
PubMed1996

Only hibernating myocardium invariably shows early recovery after coronary revascularization.

BACKGROUND: The aims of this study were to identify hibernating myocardium (hypocontractile, hypoperfused viable myocardium that regains contractility after revascularization) in the clinical setting and to predict functional outcome in patients with coronary artery disease after coronary revascularization. METHODS AND RESULTS: Preoperative data related to the anterior free wall of the left ventricle were collected in 50 coronary bypass surgery candidates (positron emission tomography [PET], [13N]NH3 for flow, and [18F]FDG for metabolism [MET]; equilibrium-gated nuclear angiography [EGNA] for regional ejection fraction [REF]; and histological data from myocardial biopsies for percentage fibrosis and viable myocytes). Three months after surgery, the patients had follow-up PET and EGNA investigations. A principal-components analysis identified four patient clusters. Cluster 1 (n = 9) had normal viable myocardium. Cluster 2 (n = 18) had viable hypocontractile myocardium (REF, 39 +/- 12%) showing a PET mismatch pattern. Cluster 3 (n = 16) had viable hypocontractile myocardium associated with morphological myocyte injury showing a matched moderate decrease in flow (66 +/- 11%) and MET (70 +/- 11%). Cluster 4 (n = 7) had hypocontractile myocardium with mainly scar tissue (fibrosis, 74 +/- 12%). After surgery, only cluster 2, with hibernating myocardium, showed significant improvement in REF (from 39 +/- 12% to 50 +/- 13%, P < .05). Cluster 3, with sites of morphological myocyte injury, showed no recovery. The stepwise logistic regression showed a combination of low preoperative REF and high MET to be the best predictor of functional recovery (P < .008). CONCLUSIONS: Multivariate analysis identifies hibernating myocardium showing early postrevascularization recovery, as opposed to viable but myolytic myocardium with no early recovery. Postrevascularization recovery can be predicted (combination of low REF and high MET) by noninvasive techniques.

Adult↗
PubMed1996

954 MHz microwaves enhance the mutagenic properties of mitomycin C.

This paper focuses on the combined effects of microwaves from mobile communication frequencies and a chemical DNA damaging agent mitomycin C (MMC). The investigation was performed in vitro by exposing whole blood samples to a 954 MHz emitting antenna from a GSM (Global System for Mobile Communication) base station, followed by lymphocyte cultivation in the presence of MMC. A highly reproducible synergistic effect was observed as based on the frequencies of sister chromatid exchanges in metaphase figures.

Cell Cycle↗
PubMed1996

Prognostic significance of bone marrow trephine and peripheral blood smears in 55 patients with mantle cell lymphoma.

Bone marrow trephine and peripheral blood smears taken at diagnosis of 55 cases of well-documented mantle cell lymphomas were reviewed in order to analyse the leukaemic involvement in this non-Hodgkin's lymphoma: its incidence, morphological characteristics and prognostic significance. A median survival of 36 months was found. The median age was 61 and the male to female ratio was 4:1. Morphologically 7 cases presented with a mantle zone pattern, all the others had a diffuse pattern. Involvement of the bone marrow was found in 58% and a trend for prolonged survival in patients with a negative trephine was seen. An absolute lymphocytosis above 10,000 mu l was found at diagnosis in 5 cases (10%) and had a statistically significant impact on survival. An additional 5 cases developed frank leukaemia during the course of the disease and died within 1 to 6 months of this evolution, suggesting that marked lymphocytosis is more a terminal event associated with an extremely poor prognosis than a presenting symptom. Finally we identified an additional parameter with statistically prognostic significance, namely, the presence of atypical cells in the peripheral blood even in the absence of an increased lymphocytosis.

Adult↗
PubMed1996

CD40 is a prognostic marker in primary cutaneous malignant melanoma.

CD40 is a receptor at the surface of B lymphocytes with important functions in the immune response. CD40 has also been found on a variety of carcinoma and melanoma cell lines where it has been suggested to serve as a possible receptor for mitogenic signals. We studied the expression and distribution of CD40 in paraffin sections of 71 uniformly treated malignant melanomas (MMs) with a long clinical follow-up using well known monoclonal antibodies. For comparison, 71 benign nevi were also studied. Common acquired nevi occasionally expressed CD40 in nests or single cells at the dermo-epidermal junction; no immunoreactivity was observed in the dermal part of acquired nevi, and all Spitz' nevi were entirely negative. One-third of large congenital nevi expressed CD40 in small clusters of heavily pigmented, epithelioid cells, corresponding to so-called proliferative nodules. In 41 of 71 MMs, CD40 was expressed in single or clustered neoplastic melanocytes; 9 cases showed CD40 expression only in the radial growth phase, and in 32 cases, the vertical growth phase showed CD40 expression. The same staining pattern was obtained with other anti-CD40 monoclonal antibodies, directed to different epitopes of the CD40 molecule. In 29 of 32 MMs showing CD40 in the vertical growth phase, expression of the CD40 ligand (CD40L) was studied; in 13 of these 29, CD40L was found in the same tumor areas that expressed CD40. Analysis of 28 metastases from 24 MM patients showed in the majority of cases a similar, scattered or nodular staining pattern as observed in the primary tumor. Patients expressing CD40 in the vertical growth phase of their MM did not differ significantly from CD40-negative patients with respect to any of the known prognostic parameters but showed a significantly shorter tumor-free survival. Patients with CD40+ CD40L+ MM tended to have a shorter tumor-free survival than those lacking CD40L. We conclude that CD40 represents a novel prognostic parameter in primary cutaneous MM. The co-localization of CD40 and CD40L suggests an autocrine growth loop in the vertical growth phase of MM.

Biomarkers, Tumor↗
PubMed1996

Three-dimensional correction for spillover and recovery of myocardial PET images.

UNLABELLED: PET permits the quantification of myocardial blood flow, but is hampered by the limited spatial resolution of PET images. METHODS: We evaluated two methods for the correction of resolution effects in PET perfusion 13NH3-ammonia images. In one model, the spillover and recovery coefficients are estimated in the kinetic modeling analysis. The new, second model uses an explicit delineation of the left ventricular wall and a convolution model for the system point spread function to compute the regional values of the spillover and recovery coefficients. RESULTS: The new method is validated with phantom measurements. The two methods are evaluated on animal experiments using 13NH3-ammonia. Both two- and three- compartment models were used to compute absolute flow values. Excellent linear correlations with microsphere data were obtained. The slope of the regression line was lower for corrections based on kinetic modeling as compared to convolution-based correction. In animal experiments, recovery coefficients of 59% for the myocardial wall and 86% for the blood pool were obtained. Spillover from the blood pool into the myocardial was was 14%. CONCLUSION: The new correction method strongly suppresses spillover and recovery effects due to limited resolution.

Algorithms↗
PubMed1995

Impaired myocardial tissue perfusion early after successful thrombolysis. Impact on myocardial flow, metabolism, and function at late follow-up.

BACKGROUND: Impaired tissue reperfusion after successful recanalization of an epicardial coronary artery has been documented both in animals and in patients with acute myocardial infarction. Whether this phenomenon can be demonstrated with positron emission tomography (PET) and whether it has an effect on late recovery of flow, metabolism, and function are unknown. METHODS AND RESULTS: Thirty patients with an acute myocardial infarction and TIMI flow grade 3 of the infarcted vessel at 90 minutes after thrombolytic therapy were studied. Within 24 hours after thrombolysis, at 5 days and at 3 months, myocardial blood flow was measured with 13NH3. 18FDG uptake was measured at 5 days. Radionuclide left ventricular angiograms were acquired at 5 days and at 3 months. In 11 patients (37%), regional myocardial flow was severely impaired (< 50% of normally perfused myocardium) despite successful thrombolysis. No recovery of left ventricular function occurred in any of these patients at 3 months. In 12 patients (40%), intermediate flows (50% to 75% of normal) were found, with functional improvement after angioplasty only in regions with a PET mismatch. Seven patients (23%) had high flow values early after successful thrombolysis (> 75% of normal) and showed preserved regional contractile function at 3 months. CONCLUSIONS: This study is the first demonstration with PET of impaired myocardial tissue perfusion in patients with an acute myocardial infarction after successful thrombolysis. Functional recovery of the reperfused myocardium is observed only when adequate tissue flow is restored. PET may be helpful in selecting patients in whom additional revascularization can improve recovery of left ventricular function.

Aged↗
PubMed1995

Regional myocardial blood flow, glucose utilization and contractile function before and after revascularization and ultrastructural findings in patients with chronic coronary artery disease.

In patients with chronic coronary artery disease, follow-up measurements of myocardial blood flow, metabolism and function were correlated with histology. In 41 patients with chronic coronary artery disease and a severely stenosed left anterior descending coronary artery, a positron emission tomographic (PET) flow/metabolism study and nuclear angiography were performed immediately before and 3 months after bypass surgery. Biopsies were taken from the left ventricular anterior wall at the time of surgery. Control biopsies were taken from donor hearts for cardiac transplantation and from hearts of patients with a defect of the atrial septum. A significant improvement of flow (P<0.01) and regional contractile function (P<0.01) was observed in the mismatch group. Glucose utilization was significantly lower (P<0.001) as compared to preoperative values. The group with preserved flow and the PET match group revealed no significant changes in flow, metabolism or function. Control biopsies revealed significantly less myolytic cells as compared to biopsies taken from both match and mismatch groups (P<0.01) and less fibrosis as compared to biopsies taken from the match group (P<0.01). Postoperatively, linear relationships were found between flow and both % fibrosis (r = 0.71, P<0.001) and regional anterior ejection fraction (r = 0.7, P<0.001). Only mismatch areas revealed significant recovery of both flow and function after revascularization with a disappearance of enhanced glucose uptake. The better linear correlation between flow and % fibrosis after surgery as compared to preoperatively was probably due to improvement of flow values in the mismatch group.

Coronary Artery Bypass↗
PubMed1995

Metabolism of nitrogen-13 labelled ammonia in different conditions in dogs, human volunteers and transplant patients.

To investigate the rate of metabolism of nitrogen-13 labelled ammonia (13NH3) in different conditions, we have determined the relative amount of unchanged 13NH3 in the blood of dogs, volunteers and transplant patients at different times following injection. In dogs, the determinations were made under basal conditions, during adenosine administration and after coronary occlusion. The results show that adenosine administration increases the metabolic rate whereas coronary occlusion does not affect 13NH3 metabolism. For both human volunteers and transplant patients the metabolic rate of 13NH3 was assessed under basal conditions and during adenosine administration. 13NH3 metabolism proceeds faster in transplant patients than in volunteers under both conditions. Adenosine administration causes a faster 13NH3 turnover in volunteers but not in transplant patients. Application of individual metabolite correction resulted in a 16% decrease in the calculated blood flow compared to uncorrected values. A smaller difference (5%) was observed between correction with mean metabolite values and individually acquired metabolite values.

Adenosine↗
PubMed1995

Cytogenetic biomonitoring of a population of children allegedly exposed to environmental pollutants. Phase 2: Results of a three-year longitudinal study.

Our previous cytogenetic biomonitoring of a group of inhabitants in a village (Mellery, Belgium) where exposure to a mixture of toxic environmental pollutants, (probably originating from a neighbouring chemical waste disposal site) was suspected, showed that difference in the SCE and HFC bioassays was more pronounced for children. The results of follow-up study in 1992 confirmed this surprising conclusion by an even higher incidence. As very few studies have been performed on the levels of children's biomarkers, this group of exposed populations needed to be explored further. Do children residing in the vicinity of hazardous waste sites indeed represent a population at higher risk? In the present study, we compare the performance of various bioassays (SCE, HFC, SSB and MN) in extended exposed and reference children's groups. Simultaneously, in the exposed group, we followed variation in the lymphocyte SCE frequencies as a function of time. Reversibility of the latter biomarker was ascertained subsequent to a preliminary technical remediation of the disposal site. We compared these data with those obtained from a synchronous cross-sectional study on a group of children living near a similar chemical disposal site. The two exposed populations did not differ from the reference population regarding to the SCE and HFC mean levels. Comparisons of the mean levels of the two other biomarkers, SSB and MN, showed no difference between the Mellery exposed children and the reference group from Wavre whereas significant differences appeared when the Hensies group is compared either to the Mellery or to the Wavre reference group.

Adolescent↗