Lysophosphatidic acid modulates intestinal epithelial cell function in vitro.
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Animals↗
Biomedical subjects
A Becker
Publications and source records attributed to A Becker.
The effect of pentylenetetrazol kindling on synaptic mechanisms of interacting glutamatergic and opioid system in the hippocampus of rats.
Endogenous opioids modulate processes of central excitability such as long-term potentiation and electrical kindling. Little is known about the neurochemical alterations in the interaction of the glutamatergic and opioid system in the development of pentylenetetrazol (PTZ) kindling in rats. Therefore, in the present study we investigated glutamate, DAMGO and naltrindole receptor binding, receptor protein expression by Western blot and ex vivo glutamate transmitter release in PTZ kindled rats. The specific 3H-DAMGO and -naltrindole binding to hippocampal membranes displayed no significant changes in kindled rats compared to controls. In contrast, the 3H-l-glutamate binding was significantly enhanced after completion of PTZ kindling. The expression of receptor protein for glutamate as well as the naloxone- and naltrindole-induced 3H-d-aspartate release from hippocampal slices did not alter in any case as a consequence of PTZ kindling. The PTZ induced enhancement of the glutamate binding sites in the hippocampus was downregulated to control level by natrindole treatment of rats prior to each PTZ application. Furthermore, naltrindole pretreatment of rats significantly inhibited the development of seizure susceptibility. In contrast, naloxone was not able to alter the seizure activity induced by PTZ as well as the transmitter receptor binding. The results are discussed in the light of a modulating role of delta-opioid receptors in PTZ kindling.
Animals↗
Serotonergic hyperinnervation of the frontal cortex in an animal model of depression, the bulbectomized rat.
We studied the influence of olfactory bulbectomy in rats on three different parameters of serotonin (5-HT) presynapses, 5-HT transporter density, tryptophan hydroxylase apoenzyme concentration, and the levels of 5-HT and 5-hydroxyindole acetic acid (5-HIAA) in various brain regions. Compared with sham-operated controls, the Bmax values of [3H]paroxetine binding, the apoenzyme concentration of tryptophan hydroxylase and the level of 5-HIAA, and, therefore, the 5-HIAA/5-HT ratio were significantly and selectively increased in the frontal cortex of bulbectomized rats, measured 12 weeks after surgery. The most likely explanation of the concomitant increase in levels of all three markers of 5-HT presynapses in the frontal cortex is an increased density of 5-HT innervation in this remote projection field of the raphe nuclei. It is suggested that the bulbectomy-associated axotomy of 5-HT fibers projecting to the bulb stimulates collateral sprouting and synaptogenesis, especially in the frontal cortex. The resulting 5-HT hyperinnervation must be expected to alter global neuronal activity in this region and to impair the balance of information flow between this and other brain regions, resulting in a multitude of secondary behavioral and neurochemical changes. The frontocortical abnormalities observed by brain imaging studies in the brains of depressed patients may also be explained by a selective 5-HT hyperinnervation of this brain region.
Animals↗
Effects of anticonvulsive drugs on pentylenetetrazol kindling and long-term potentiation in freely moving rats.
Drugs with anticonvulsive properties and different mechanisms of action were compared for their influence on long-term potentiation and pentylenetetrazol kindling in freely moving animals. Rats were chronically implanted with a stimulation electrode in the angular bundle and a recording electrode in the dentate gyrus. Field potentials in the dentate gyrus were elicited and long-term potentiation was induced by stimulation of the perforant pathway. The clinically used drugs or the potentially anticonvulsive drugs, diphenylhydantoin (50 mg/kg), diazepam (0.5 mg/kg), pentobarbital (10 mg/kg), dizocilpine (MK 801, 0.2 mg/kg) and CGP 43487 (2-amino-4-methyl-5-phosphono-3-pentenoic acid-carboxyethylester, 10 mg/kg), were injected before tetanization. In behavioural experiments pentylenetetrazol kindling was performed with pretreatment with the substances in dosages indicated above (except MK 801, 0.3 mg/kg). Field potentials recorded in the interval between drug administration and tetanization were influenced only by diphenylhydantoin which enhanced the population spike amplitude to 128% of control values. However, the substances showed different effects on long-term potentiation. MK 801, CGP 43487 and pentobarbital depressed potentiation; diazepam was without effect. Diphenylhydantoin had a minor influence on induction but significantly impaired maintenance of long-term potentiation. Furthermore, MK 801, CGP 43487, diazepam and pentobarbital differentially depressed kindling whereas phenytoin only slightly influenced it. The consequences as to hypothetical common cellular mechanisms for kindling development and long-term potentiation are discussed.
Animals↗
Electrical current generation and proton pumping catalyzed by the ba3-type cytochrome c oxidase from Thermus thermophilus.
Several amino acid residues that have been shown to be essential for proton transfer in most cytochrome c oxidases are not conserved in the ba3-type cytochrome c oxidase from the thermophilic eubacterium Thermus thermophilus. So far, it has been unclear whether the Th. thermophilus ba3-type cytochrome c oxidase can nevertheless function as an electrogenic proton pump. In this study, we have combined charge translocation measurements on a lipid bilayer with two independent methods of proton pumping measurements to show that enzymatic turnover of the Th. thermophilus cytochrome c oxidase is indeed coupled to the generation of an electrocurrent and proton pumping across the membrane. In addition to a 'vectorial' consumption of 1.0 H+/e- for water formation, proton pumping with a stoichiometry of 0.4-0.5 H+/e- was observed. The implications of these findings for the mechanism of redox-coupled proton transfer in this unusual cytochrome c oxidase are discussed.
Amino Acid Sequence↗
Protective effects of cortistatin (CST-14) against kainate-induced neurotoxicity in rat brain.
Cortistatin (CST-14) is a recently discovered endogenous peptide which shares similarity to somatostatin and binds to somatostatin receptors. In this study, we show that CST-14 exhibits anticonvulsive and neuroprotective effects in rats. Injection of rats with kainic acid (KA; 10 mg/kg; i.p.) generated a strong seizure activity which was attenuated by the i.c.v. application of 1 and 10 nmol CST-14 when given 10 min before KA. Moreover, 3 days after KA injection, a marked loss of neurons in cortex and hippocampus of rats was observed which was inhibited by pretreatment with CST-14. An immunohistochemical analysis using specific antibodies revealed that KA reduced immunoactive sst2A and sst3 somatostatin receptors in the hippocampus-an effect which was largely prevented by pretreatment with CST-14. Superfusion of hippocampal slices with CST-14 also reduced the stimulated release of 3H-d-aspartate. We conclude that CST-14 exerts neuroprotective effects by binding to somatostatin receptors which in turn leads to a reduced release of excitotoxic neurotransmitters.
Animals↗
Oxygenation of squamous cell carcinoma of the head and neck: comparison of primary tumors, neck node metastases, and normal tissue.
BACKGROUND: Most previous oxygenation measurements of head and neck tumors have mainly been performed in neck nodes. We investigated, therefore, the relationship between the pO2 status of primary tumors, cervical neck node metastases and normal tissues. PATIENTS AND METHODS: 30 patients with histologically proven advanced stage III-IV squamous cell carcinoma of head and neck underwent pretreatment polarographic pO2 measurements with a pO2 histograph (Eppendorf, Hamburg, Germany). We obtained data on oxygenation of 23 primary tumors, of 22 neck node metastases, and of 30 contralateral sternocleidomastoid muscles. In 15 cases, we were able to perform measurements in all three regions in the same individual. results: A highly significant correlation existed between the median pO2 of primary tumors and their neck node metastases (p=0.0001), as well as between the proportion of pO2 values < or =2.5 mmHg and +/-5.0 mmHg (p=0.0001, p=0.001) in both anatomic sites. The average pretreatment median PO2 was 14.7 mmHg (range 0.2-58.5 mmHg) in primary tumors, 13.7 mmHg (range 1.9-50.3 mmHg) in neck node metastases, and 43.8 mmHg (range 20.8-67.7 mmHg) in sternocleidomastoid muscles. In all cases, the oxygenation of malignant tissue was below that of the corresponding muscle. There was also a weak, but significant, correlation between hemoglobin level and the median pO2 of the primary tumors, as well as between hemoglobin concentration and the proportion of values below 5 mmHg at the primary site (p=0.017, p=0.003). CONCLUSIONS: Primary tumors and their regional lymph node metastases in advanced squamous cell carcinoma of the head and neck show comparable patterns of oxygenation in terms of the median pO2 and the proportion of hypoxic measurements. This report suggests that, in patients with such carcinomas, the oxygenation data obtained at one site are related to tumor oxygenation at other sites, so that measurements in any anatomic site would be sufficient to estimate a tumor's oxygenation status. The weak correlation between pO2 and hemoglobin level requires further investigation.
Adult↗
Hypertrehalosaemic neuropeptides decrease levels of the glycolytic signal fructose 2,6-bisphosphate in cockroach fat body
In cockroach fat body, trehalogenesis and glycolysis compete for glucose phosphates as common substrates. During trehalogenesis, glycolysis is inhibited, although the mechanism responsible for this is not known. Incubation of the isolated fat body from the Argentine cockroach Blaptica dubia with an extract of the corpora cardiaca containing as little as 0.005 gland equivalents ml-1 of incubation medium increased the release of trehalose (anthrone-positive material) from the tissue by more than 100 %. The content of the glycolytic activator fructose 2,6-bisphosphate was decreased by up to 50 %. A decapeptide was isolated from the corpora cardiaca of B. dubia and shown to be identical to the naturally occurring Blaberus discoidalis hypertrehalosaemic peptide (Bld HrTH), which was also found in the corpora cardiaca. Synthetic Bld HrTH at 2 nmol l-1 and above increased trehalose production and decreased the content of fructose 2,6-bisphosphate to the same extent as did corpus cardiacum extract. The octapeptides Periplaneta americana cardioacceleratory hormones I and II (Pea CAH-I and Pea CAH-II) also had a significant effect on both parameters. Fructose 2,6-bisphosphate is a potent activator of phosphofructokinase from cockroach fat body if the enzyme is assayed at near-physiological concentrations of substrates and effectors. It is suggested that, because of the decrease in fructose 2,6-bisphosphate levels in the fat body, the activity of the key glycolytic enzyme phosphofructokinase is diminished. This can explain the inhibition of glycolytic flux by hypertrehalosaemic peptides which alters the balance of glucose metabolism in favour of trehalose formation.
Journal Article↗
Isolation and crystallization of functionally competent Escherichia coli peptide deformylase forms containing either iron or nickel in the active site.
Three metallo forms of peptide deformylase (PDF, EC 3.5.1.31) of Escherichia coli were prepared and crystallized (space group C2, diffraction limit 1.9 A) for initiating the X-ray structure determination of the metal center in correlation with the catalytic functionality of this enzyme. The native Fe2+ containing enzyme species was directly isolated from overproducing bacteria by using catalase as a buffer additive, which stabilizes the catalytic activity against oxidative destruction. The Ni2+ containing form, which is oxygen-insensitive, was obtained by metal exchange with free Ni2+ and found to be catalytically equally effective (kcat/KM = 10(5) M-1 s-1 for N-formyl-Met-Ala). The Zn2+ form, prepared from the apoenzyme or by displacement of bound Ni2+ by free Zn2+, proved virtually inactive.
Amidohydrolases↗
Structure of peptide deformylase and identification of the substrate binding site.
Peptide deformylase is an essential metalloenzyme required for the removal of the formyl group at the N terminus of nascent polypeptide chains in eubacteria. The Escherichia coli enzyme uses Fe2+ and nearly retains its activity on substitution of the metal ion by Ni2+. We have solved the structure of the Ni2+ enzyme at 1.9-A resolution by x-ray crystallography. Each of the three monomers in the asymmetric unit contains one Ni2+ ion and, in close proximity, one molecule of polyethylene glycol. Polyethylene glycol is shown to be a competitive inhibitor with a KI value of 6 mM with respect to formylmethionine under conditions similar to those used for crystallization. We have also solved the structure of the inhibitor-free enzyme at 2.5-A resolution. The two structures are identical within the estimated errors of the models. The hydrogen bond network stabilizing the active site involves nearly all conserved amino acid residues and well defined water molecules, one of which ligates to the tetrahedrally coordinated Ni2+ ion.
Amidohydrolases↗
Montelukast for chronic asthma in 6- to 14-year-old children: a randomized, double-blind trial. Pediatric Montelukast Study Group.
CONTEXT: Leukotrienes are important mediators of asthma by causing bronchoconstriction, mucous secretion, and increased vascular permeability. Studies using compounds that block leukotrienes have demonstrated improvement in asthma control in adults and adolescents, but children younger than 12 years, for whom asthma is the most common chronic disease, have not been studied. OBJECTIVE: To determine the clinical effect of montelukast, a leukotriene receptor antagonist, in 6- to 14-year-old children with asthma. DESIGN: Eight-week, multicenter, randomized, double-blind study. SETTING: Forty-seven outpatient centers at private practices and academic medical centers in the United States and Canada. PATIENTS: A total of 336 children with forced expiratory volume in 1 second (FEV1) between 50% to 85% of the predicted value, at least 15% reversibility after inhaled beta-agonist administration, a minimal predefined level of daytime asthma symptoms, and daily beta-agonist use. Concomitant inhaled corticosteroids at a constant daily dose were used by 39% of patients receiving montelukast and 33% receiving placebo. INTERVENTION: After a 2-week placebo run-in period, patients received either montelukast (5-mg chewable tablet) or matching-image placebo once daily at bed-time for 8 weeks. MAIN OUTCOME MEASURE: Morning FEV1 percent change from baseline. RESULTS: Mean morning FEV1 increased from 1.85 L to 2.01 L in the montelukast group and from 1.85 L to 1.93 L in the placebo group. This represents an 8.23% (95% confidence interval [CI], 6.33% to 10.13%) increase from baseline in the montelukast group and a 3.58% (95% CI, 1.29% to 5.87%) increase from baseline in the placebo group (P<.001 for montelukast vs placebo). CONCLUSION: Montelukast improves morning FEV1 in 6- to 14-year-old children with chronic asthma.
Acetates↗
The role of microbial surface polysaccharides in the Rhizobium-legume interaction.
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Carbohydrate Conformation↗
A 2-week pretreatment with 13-cis-retinoic acid + interferon-alpha-2a prior to definitive radiation improves tumor tissue oxygenation in cervical cancers.
BACKGROUND: We have evaluated the tumor tissue pO2 in cervical cancers in patients treated with 13-cis-retinoic acid and interferon-alpha-2a prior to and during radiotherapy. PATIENTS AND METHODS: From June 1995 through April 1997, 22 patients with squamous cell carcinoma FIGO IIB/III of the cervix who were scheduled for definitive radiotherapy with curative intent received additional treatment with 13-cis-retinoic acid (cRA, isotretinoin) plus interferon-alpha-2a (IFN-alpha-2a) as part of a phase-II protocol. cRA/IFN-alpha-2a started 14 days prior to radiotherapy (1 mg per kilogramme body weight cRA orally daily plus 6 x 10(6) IU IFN-alpha-2a subcutaneously daily). After this induction period, standard radiotherapy was administered (external irradiation with 50.4 Gy in 28 fractions of 1.8 Gy plus HDR-brachytherapy). During radiotherapy, cRA/IFN-alpha-2a treatment was continued with 50% of the daily doses. Tumor tissue pO2-measurements were performed prior to and after the cRA/IFN-induction period as well as at 20 Gy and at the end of radiotherapy with an Eppendorf-pO2-histograph. RESULTS: In 11 out of the 22 patients, pO2-measurements were performed prior to the cRA/IFN-induction therapy. The median pO2 of these untreated tumors was 17.7 +/- 16.3 mm Hg. The relative frequency of hypoxic readings with pO2-values below 5 mm Hg ranged from 0% to 60.6% (mean 24.3 +/- 21.0%). After the 2-week induction period with cRA/IFN, the median pO2 had increased from 17.7 +/- 16.3 mm Hg to 27.6 +/- 19.1 mm Hg (not significant). In all 5 patients with hypoxic tumors prior to cRA/IFN (median pO2 of 10 mm Hg or less), the median pO2 was above 20 mm Hg after the 2-week cRA/IFN-induction. In this subgroup of hypoxic tumors, the median pO2 increased from 6.3 +/- 2.7 mm Hg to 27.0 +/- 5.6 mm Hg (p = 0.004, t-test for paired samples). The frequency of hypoxic readings (pO2-values < 5 mm Hg) decreased from 44.7 +/- 17.1% to 2.0 +/- 2.5% (p = 0.012, t-test for paired samples). There was, however, no obvious volume reduction after 14 weeks of cRA/IFN on clinical examination. A complete clinical remission of the local tumor was observed in 19/22 patients after radiotherapy and additional cRA/IFN-alpha-2a-treatment. In primarily hypoxic tumors (with a median pO2 below 10 mm Hg prior to treatment), 4/5 achieved complete remission. CONCLUSIONS: Pretreatment with cRA/IFN improves oxygenation of primarily hypoxic cervical cancers. The mechanisms of action remain unclear and further investigation of the combination regimen is recommended.
Aged↗
[Oxygenation status of squamous cell carcinoma of the head and neck: comparison of primary tumors, their neck node metastases and normal tissue].
AIM: Investigation of the relationship between the pO2-status of primary tumors, their cervical neck node metastases and normal tissues in squamous cell carcinomas of the head and neck. PATIENTS AND METHODS: Pretreatment oxygenation of primary tumors, their neck node metastases and of the contralateral sternocleidomastoid muscle was assessed in 16 patients with histologically proven advanced squamous cell carcinomas of head and neck. Oxygenation was measured with a polarographic microelectrode system (Eppendorf-pO-Histograph). Using CT/MRT additionally the volume of the tumors was estimated. RESULTS: A highly significant correlation existed between the median pO2 of primary tumors and their neck node metastases and between the relative proportion of hypoxic values (< 5 mm Hg) of both anatomic sites (both p = 0.0001) (Figure 1). Primary tumors were not different from their neck node metastases, neither regarding the pO2 median values nor in view of the relative frequency of hypoxic values (Table 1). No correlation was found between the volume of primary tumors and the one of their neck node metastases. For volume of tumors and the oxygenation status no relationship was found as well. Significantly different was the median pO2 in the muscles from the one of the malignant tissues (p = 0.0004). CONCLUSION: The results suggest that for to estimate the oxygenation status of squanious cell carcinomas of the head and neck pO2 measurements of primary tumors and neck node metastases are equally sufficient.
Carcinoma, Squamous Cell↗
Chromosomal in-vitro radiosensitivity of lymphocytes in radiotherapy patients and AT-homozygotes.
BACKGROUND: We investigated the in-vitro radiosensitivity of peripheral blood lymphocytes with a special FISH/CISS-technique. PATIENTS AND METHODS: From October 1993 through April 1996, a total number of 52 cancer patients was enrolled in the study. The tumor sites in these patients were: breast (n = 41), lung (n = 4), head and neck (n = 3) as well as prostate, bladder, rectal cancer and Hodgkin's disease (each n = 1). Twenty-six of them were examined prior to planned radiotherapy (prospective group) and 26 after radiotherapy (retrospective group). Three additional individuals (without cancer or radiotherapy) with proven ataxia telangiectasia (Louis-Bar syndrome, AT-homozygotes) were also investigated and their blood samples served as positive control for radiosensitivity. The clinical radiation response of normal tissue in radiotherapy patients was scored according to the WHO grading system for acute and according to the RTOG grading system for late effects. For to estimate the intrinsic radiosensitivity, blood samples were taken and irradiated in vitro with 0 (control) or 0.7 or 2 Gy with a 6 MV-linear accelerator, standard 48-hour lymphocyte cultures were prepared, chromosomes #1, #2 and #4 were simultaneously labeled with a FISH/CISS-technique and 200 to 1,000 metaphase spreads were scored for chromosomal aberrations. The radiation sensitivity of lymphocytes was expressed as the number of radiation-induced chromosomal breaks per mitosis after 0.7 Gy or 2 Gy corrected for the 0-Gy control value. RESULTS: The frequency of chromosomal breaks/mitosis in the unirradiated control lymphocytes was 0.020 +/- 0.015 in prospective patients who had not yet received radiotherapy. It was significantly higher in retrospective patients (0.264 +/- 0.164 breaks/mitosis) as a result of the previous radiation exposure. The 3 AT-homozygotes showed also an increased number of spontaneous chromosomal breaks (0.084 +/- 0.016 breaks/mitosis), probably resulting from the chromosomal instability in this disease. This figure, however, was significantly lower than in retrospective patients. The number of radiation-induced breaks after in-vitro irradiation was comparable in lymphocytes of patients who showed no normal tissue reaction (n = 11) as compared to those with mild to moderate radiation reaction (n = 32, acute reactions Grade 1 to 2, late reactions Grade 0 to 2). In 9 patients with unexpected severe plus late Grade 3 to 4 reactions, however, a significantly higher number of radiation-induced chromosomal breaks was measured; the highest number was observed in a patient with a radiation myelitis. The 3 AT-homozygotes showed, as expected, an extreme radiosensitivity of their lymphocytes. The number of breaks/mitosis after 0.7 Gy in vitro irradiation of lymphocytes was 0.103 +/- 0.059 in patients with no normal tissue radiation reaction (n = 11), 0.122 +/- 0.146 in the group with mild to moderate radiation reactions Grade 1 to 2 (n = 32), 0.359 + 0.226 in patients with unexpected Grade 3 to 4 normal tissue reactions (n = 9) and 0.550 +/- 0.243 in the 3 AT-homozygotes (p < 0.01, t-test). The difference in lymphocyte radiosensitivity between these 4 groups was also detected after in-vitro irradiation with 2 Gy (0.484 +/- 0.132 vs. 0.535 +/- 0.228 vs. 0.926 +/- 0.349 vs. 1.423 +/- 0.072). CONCLUSIONS: We found a significantly higher number of chromosomal breaks in lymphocytes of patients with severe or extreme radiation reaction of normal tissues as compared to patients with no or only mild to moderate radiation reactions. The radiosensitivity of lymphocytes in these radiosensitive patients was in the range between normal radiosensitivity and the radiosensitivity of AT-homozygotes. Detection of patients with severely enhanced intrinsic radiosensitivity might be possible with this method.
Adult↗
[Significance of calcium detection with electron-beam tomography in coronary disease].
PURPOSE: Coronary calcium is a powerful indicator of arteriosclerosis and can be detected very precisely with electron beam tomography. The method can be applied in patients with known coronary artery disease or in asymptomatic patients at risk of arteriosclerotic disease. METHODS: The standard protocol of EBT consists of 30 to 40 slices of 3-mm thickness with a scan time of 100 ms, no overlap. No contrast medium is needed. The total scan can be performed within one breathhold. The calcium score is calculated as described by Agatston. Radiation exposure amounts to 0.8 mSv per total screen. We used spiral CT with and without ECG trigger as an alternative. RESULTS: At the University of Munich we performed an EBT scan of the heart in 1100 patients within the last year. In 567 patients coronary angiography was performed also (+/- 3 days). Confirming previous reports in the literature, we found a correlation of the calcium score with the age and gender of the patients. Severe coronary artery disease (stenoses > or = 75%) was associated with significantly more calcium than less severe CAD. The calcium score did not discriminate between one-, two- and three-vessel disease. The site of calcification does not correlate with the localization of stenoses. Thirty-three percent of the patients with significant coronary artery disease showed a normal age-adjusted calcium score; a total of 8.1% of patients with severe stenoses did not reveal any coronary calcification (score = 0). With asymptomatic patients there are only a few studies available. Soft plaques cannot be detected with EBT, but in most patients soft plaques occur together with hard plaques. Our results show that spiral CT of the newest generation may also be used for calcium screening. There was an excellent correlation of the calcium scores of EBT and spiral CT at all levels of calcification. DISCUSSION: Coronary calcium is a sensitive marker of coronary artery disease. In the clinical setting EBT is indicated in patients with known coronary artery disease (to evaluate prognosis), in patients who are unable to perform a stress test, and in patients with atypical chest pain. However, lack of calcification may be associated with severe stenoses in a minority of patients. The clinical value in asymptomatic patients needs to be defined: randomized studies are necessary. We see a possible indication in patients with known risk factors, in whom primary preventive strategies could be performed more selectively and cost-effectively.
Adolescent↗
[Methods of quantification of coronary artery calcifications with electron-beam and conventional computed tomography].
PURPOSE: To compare electron beam CT (EBCT) und prospectively ECG gated conventional CT for the detection and quantification of coronary artery calcifications. METHODS: 42 patients (mean age 62.8 +/- 8.8 years) were scanned, both with EBCT and ECG gated sequential CT. For quantification, the traditional "total calcium score" (TCS) according to the Agatson method as well as the "volumetric calcium score" (VCS) as determined with a stand-alone workstation (NetraMD) was calculated for both modalities. RESULTS: There was close correlation between EBCT and conventional CT, both for TCS (r = 0.984) as well as for VCS (r = 0.986) score values. The median difference was 17% for TCS and 13% for VCS. The difference between the two modalities was not statistically significant (p = 0.44). CONCLUSION: EBCT and prospectively ECG triggered conventional CT are equivalent for the quantification of coronary artery calcifications. The extent of calcifications can be established with both modalities using either TCS or VCS score values.
Age Factors↗
[Significance of electron-beam tomography in the evaluation of the patency of aortocoronary bypasses].
PURPOSE: Electron beam tomography (EBT) permits acquisition of images with high spatial and temporal resolution. The value of EBT and other imaging modalities for the depiction of patent coronary artery bypass grafts (ACVB, IMA) are compared to coronary angiography and an overview of current results is given. MATERIAL AND METHODS: Graft patency can be evaluated with indirect methods stress, such as echocardiography, radionuclide ventriculography, myocardial scintigraphy, positron-emission tomography (PET) and direct imaging modalities, such as Doppler/2D echocardiography, EBT, spiral computed tomography (SCT) and magnetic resonance angiography (MRA). RESULTS: With indirect methods graft patency can be evaluated with sensitivity of 64-100% and specificity of 73-100%. EBT and SCT are equivalent in sensitivity (= 94%) in the assessment of open venous grafts and specificity is up to 100%, but EBT is superior in the diagnosis of patent IMA grafts (sensitivity 100% vs 89%). Visualization of high-grade venous bypass stenosis seems possible with EBT. MRA with gradient echo technique is highly accurate in the assessment of patent venous grafts (sensitivity 77-93%) but has limited value in the evaluation of IMAs (sensitivity = 53%). Promising are ultrafast 3D-MRA methods which permit high accuracy (sensitivity = 94-96%) in assessing venous and arterial grafts. DISCUSSION: Indirect imaging methods cannot differentiate between an occluded bypass, progression of coronary artery disease and myocardial infarction. EBT and SCT are equivalent in the diagnosis of open and occluded venous grafts, but EBT is superior in the assessment of patent IMA grafts. Visualization of high-grade venous bypass stenosis seems possible with EBT. MRA techniques, especially ultrafast 3D-MR methods, are highly accurate in the assessment of patent venous and arterial grafts but are still limited to scientific research.
Coronary Artery Bypass↗