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Biomedical subjects

A Reimann

Publications and source records attributed to A Reimann.

At least 19 recordsLinked to original sources
PubMed2006

Sixty-four-MSCT in the characterization of porcine acute and subacute myocardial infarction: determination of transmurality in comparison to magnetic resonance imaging and histopathology.

OBJECTIVE: The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. MATERIALS AND METHODS: Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland-Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. RESULTS: Close spatial agreement was observed for MRI-MO and MSCT-MO (bias=0.55; CI=-1.49 to 2.60 at 5 min MSCT), TTC and MSCT-LE (bias=-1.28; CI=-3.76 to 1.19) or MRI-LE and MSCT-LE (bias=-0.79; CI=-4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa=0.93) and high agreement for transmural extent of TTC, MRI-LE and MSCT-LE (weighted kappa=0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa=0.33; 0.44). CONCLUSIONS: MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

Analysis of Variance↗
PubMed2006

Late myocardial enhancement assessed by 64-MSCT in reperfused porcine myocardial infarction: diagnostic accuracy of low-dose CT protocols in comparison with magnetic resonance imaging.

The purpose was to assess the practicability of low-dose CT imaging of late enhancement in acute infarction. Following temporary occlusion of the second diagonal branch, seven pigs were studied by multislice computed tomography (MSCT) and magnetic resonance imaging (MRI). Thus, 64-slice CT was performed at 3, 5, 10 and 15 min following the injection of contrast medium according to a bolus/low-flow protocol. Standard parameters of 120 kV and 800 mAs were compared with 80 kV and 400 mAs in various combinations. Infarct volumes were assessed as percentage of the ventricle for both MSCT and MR images. CT density values for viable and infarcted myocardium were obtained and image quality assessed. Mean infarct volume as measured by MRI was 12.33+/-7.06%. MSCT achieved best correlation of volumes at 5 and 10 min. Whilst lowering of tube current resulted in poor correlation, tube voltage did not affect accuracy of infarct measurement (r (2)=0.92 or 0.93 at 5 min, 800 mAs and 80 or 120 kV). In terms of image quality, greater image noise with 80 kV was compensated by significantly better contrast enhancement between viable and non-viable myocardium at lower voltage. Myocardial viability can accurately be assessed by MSCT at 80 kV, which ensures higher contrast for late enhancement and yields good correlation with MRI.

Analysis of Variance↗
PubMed2006

Non-invasive coronary angiography with 16-slice spiral computed tomography: image quality in patients with high heart rates.

The purpose of this study was to assess segment image quality at high heart rates using 16-slice computed tomography and differential reconstruction for major coronary vessels. According to the following protocol, 16-slice CT coronary angiography in 46 patients with a mean heart rate of 86.3+/-11.8 was reconstructed. At three transverse planes, preview series were obtained and motion artifacts evaluated in 5% increments from 0-95% within the cardiac cycle. Relying on image quality in the previews, reconstructions were performed at three z-positions for each patient. Segment image quality was assessed in terms of artifacts and visibility. The effects of heart rate and trigger delay on image quality were analyzed. Optimal image quality was achieved at 25 to 35% of the cardiac cycle for the left circumflex (CX) and right coronary artery (RCA) or 30 to 40% for the left main (LM) and left anterior descending artery (LAD). Sixteen-slice CT and differential reconstruction produced good image quality with a low percentage of motion-degraded proximal and middle segments (8.8%). Grades were 1.5 for the LM, 1.9 for the LAD, 2.0 for the CX and 2.3 for the RCA. At high heart rates, good image quality of the coronary arteries is achieved by 16-slice CT and a sophisticated reconstruction strategy at peak to late systole.

Algorithms↗
PubMed2006

Image quality and diagnostic accuracy of 16-slice multidetector computed tomography for the detection of coronary artery disease in obese patients.

BACKGROUND: Cardiac multislice spiral computed tomography (MSCT) scanners permit visualization of the coronary arteries with an overall good sensitivity (sens) and specificity (spec). However, in obese patients (pts), who are at higher risk to develop coronary artery disease (CAD), image quality of MSCT is supposed to be limited. At present, there are no data whether the accuracy of MSCT depends on the body mass index (BMI). Thus, we compared the catheter-controlled MSCT results from normal weight and obese pts in a cohort of 117 pts with regard to sens, spec, positive predictive value (PPV), negative predictive value (NPV) and image quality. METHODS AND MATERIAL: In all, 21 normal weight pts (group I: BMI<25, 64.6+/-11.1 years, number of risk factors 2.1+/-1.1), 60 pts with mild overweight (group II: BMI 25-30, 64.6+/-8.9 years, number of risk factors 3.4+/-1.0) and 36 obese pts (group III: BMI >30, 63.0+/-8.5 years, number of risk factors 3.4+/-0.9) were examined by MSCT (Sensation 16 Speed 4 D((R)), Siemens, Germany, gantry rotation time 375 ms) and invasive coronary angiography. MSCT results were compared blinded to the results of the coronary angiography with regard to the presence or absence of a significant stenosis (>50%) in a modified AHA 13 segment (sgt) model. Image quality was assessed on a qualitative scale between 1 (very good) and 5 (insufficient image quality) for each sgt. RESULTS: Sens, spec, PPV and NPV were statistically not different in all three groups (I: 0.88/0.97/0.91/0.96, II: 0.83/0.97/0.88/0.95, III: 0.87/0.99/0.96/0.96). 3 pts (group I 1, group II 2) had to be excluded from analysis due to technical problems. Group I had significantly less risk factors (P < 0.001) and image quality was significantly better than in group II and III (P < 0.05). Group II and III did not differ with regard to risk factors or image quality. CONCLUSIONS: Overweight and obesity have an impact on MSCT image quality but did not hamper the diagnostic accuracy. Thus, MSCT is a noninvasive method to detect or rule out CAD also in pts with higher BMI. These retrospective data have to be confirmed in larger prospective trials.

Aged↗
PubMed2004

Age associated changes of AGE-receptor expression: RAGE upregulation is associated with human heart dysfunction.

The binding of advanced glycation endproducts (AGEs) to their receptors is known to cause changes in cell function during normal ageing and is implicated in the pathogenesis of cardiovascular disease. In this study, expression of the AGE-receptor 3 (AGE-R3) and the receptor for AGEs (RAGE) was compared on the mRNA and protein level in the ageing human heart. Western blot and RT-PCR analysis of the AGE receptors from the cardiac auricles in senescent and adult patients was performed and compared with young controls. Whereas the expressions of AGE-R3 as well as RAGE protein were significantly upregulated in the senescent population, only the upregulation of RAGE is associated with reduced heart function. Therefore, our results support a pathophysiological function for RAGE in the ageing human heart.

Adult↗
PubMed2001

Detoxification of lignocellulose hydrolysates with ion-exchange resins.

Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD-8). A dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the anion exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment with XAD-8.

Cellulose↗
PubMed2000

Influence of lignocellulose-derived aromatic compounds on oxygen-limited growth and ethanolic fermentation by Saccharomyces cerevisiae.

Phenolic compounds released and generated during hydrolysis inhibit fermentation of lignocellulose hydrolysates to ethanol by Saccharomyces cerevisiae. A wide variety of aromatic compounds form from lignin, which is partially degraded during acid hydrolysis of the lignocellulosic raw material. Aromatic compounds may also form as a result of sugar degradation and are present in wood as extractives. The influence of hydroxy-methoxy-benzaldehydes, diphenols/quinones, and phenylpropane derivatives on S. cerevisiae cell growth and ethanol formation was assayed using a defined medium and oxygen-limited conditions. The inhibition effected by the hydroxy-methoxy-benzaldehydes was highly dependent on the positions of the substituents. A major difference in inhibition by the oxidized and reduced form of a diphenol/quinone was observed, the oxidized form being the more inhibitory. The phenylpropane derivatives were examined with respect to difference in toxicity depending on the oxidation-reduction state of the gamma-carbon, the presence and position of unsaturated bonds in the aliphatic side chain, and the number and identity of hydroxyl and methoxyl substituents. Transformations of aromatic compounds occurring during the fermentation included aldehyde reduction, quinone reduction, and double bond saturation. Aromatic alcohols were detected as products of reductions of the corresponding aldehydes, namely hydroxy-methoxy-benzaldehydes and coniferyl aldehyde. High molecular mass compounds and the corresponding diphenol were detected as products of quinone reduction. Together with coniferyl alcohol, dihydroconiferyl alcohol was identified as a major transformation product of coniferyl aldehyde.

Aerobiosis↗
PubMed1999

Use of an intraaortic balloon pump in patients with impaired left ventricular function.

Prophylactic use of an intraaortic balloon pump (IABP) prior to open-heart surgery in patients with impaired left ventricular function is still under debate. Patients with left ventricular ejection fraction (LVEF) < 40% were therefore compared according to time of IABP placement, viz. preoperative (n = 56), intraoperative (n = 40) or postoperative (n = 17), and also with patients who did not receive mechanical support despite LVEF < 40% (n = 78). The main indication for preoperative IABP insertion was severely impaired left ventricular function (80%), while patients with intraoperative or postoperative IABP placement mainly presented with low cardiac-output syndrome (70%/53%). Preoperative IABP was associated with a low mortality rate (8.9%), whereas patients with intraoperative or postoperative IABP placement had a high mortality risk and an increased catecholamine requirement. Of the patients scheduled for surgery without prophylactic IABP, 19% required intra- or postoperative insertion. Prophylactic placement of IABP thus reduced the mortality rate as well as the postoperative need for mechanical and catecholamine support. Need for intraoperative IABP insertion was associated with high mortality, whereas the outcome after postoperative IABP placement depended on the indication for the measure.

Aged↗
PubMed1997

Immunity to cartilage link protein in patients with juvenile rheumatoid arthritis.

OBJECTIVE: To determine whether children with juvenile rheumatoid arthritis (JRA) express cellular immunity to cartilage link protein. METHODS: Link protein was purified from human fetal epiphyseal and bovine adult nasal cartilage. It was used in proliferation assays with the peripheral blood lymphocytes isolated from 54 children with JRA and 22 nonarthritic controls. RESULTS: Patients with JRA expressed a significantly higher prevalence of cellular proliferation to human link protein compared with the control group, independent of whether they had pauciarticular, polyarticular, or systemic disease. In the case of bovine link protein, significant differences were only noted for the polyarticular group. There was significant correlation between the immunity to bovine and to human link proteins. Furthermore, immune responses to both molecules correlated with measures of joint disease activity. CONCLUSION: These results suggest that immunity to link protein may play a role in the pathogenesis of JRA.

Adolescent↗
PubMed1996

Effects of bacterial lipopolysaccharides (LPS) and tumour necrosis factor-alpha (TNF alpha) on rat tracheal epithelial cells in culture: morphology, proliferation and induction of nitric oxide (NO) synthase.

Rat tracheal epithelial cells were cultured and the effects of LPS and TNF alpha on cell morphology, rate of proliferation and NO synthase activity were studied. NO synthase activity was determined by measuring the accumulation of 3H-L-citrulline during incubation of confluent monolayer with 3H-L-arginine. In untreated cells no significant 3H-L-citrulline formation was detected, and bradykinin and the calcium ionophore A 23187 failed to stimulate 3H-L-citrulline formation excluding a constitutively expressed, calcium-dependent NO synthase activity. After culturing the cells for 18 h in the presence of LPS (10 micrograms/ml) and TNF alpha (500 U/ml) a marked formation of 3H-L-citrulline could be detected, which was largely inhibited by N(G)-monomethyl-L-arginine (L-NMMA) indicating the induction of NO synthase activity which could be prevented by dexamethasone. Exposure of confluent monolayer to LPS and TNF alpha for up to 4 days resulted in a reduction in cell density by 20% within 1 to 2 days and in additional marked changes in cell morphology. The normal honeycomb-like structure of the culture was lost and a considerable number of cells developed "dendritic' outgrowths. These morphological changes as well as the reduction in cell density was attenuated by dexamethasone, but not by the NO synthase inhibitor L-NMMA. The rate of cell proliferation was determined in non-confluent cultures 24 h after passage by determination of the incorporation of tritium into DNA during 24 h of incubation with 3H-thymidine. 3H-thymidine incorporation was reduced by about 40-45% when LPS or TNF alpha was present during exposure to 3H-thymidine, and by about 65%, when LPS and TNF alpha were present in combination. Neither L-NMMA nor dexamethasone significantly affected the 3H-thymidine incorporation nor the inhibitory effects of LPS and TNF alpha. In conclusion, airway epithelial cells are markedly affected by LPS and TNF alpha and the various responses (changes in the cell morphology, inhibition of cell proliferation and induction of NO synthase activity) appear to be caused by different (dexamethasone-sensitive and -insensitive), cellular mechanisms. An enhanced formation of endogenous NO may not be responsible for the observed morphological changes or the inhibition of cell proliferation.

Animals↗
PubMed1996

Regulation of 5-HT release from enterochromaffin cells.

Large amounts of 5-HT are present in the mammalian intestine where the amine is concentrated in the enterochromaffin cells (ECs) of the mucosa. ECs have the enzymes to synthesize 5-HT, are endowed with a specific, imipramine-sensitive 5-HT uptake mechanism and can store 5-HT in specific secretory vesicles. ECs can secrete 5-HT in a calcium-dependent manner. In particular, calcium influx through voltage-regulated channels and receptor-mediated liberation of intracellular calcium can evoke 5-HT release. 5-HT secretion from ECs occurs predominantly at the interstitial side and is controlled by a complex pattern of receptor-mediated mechanisms. Stimulatory receptors (beta-adrenoceptors, muscarine, nicotine and 5-HT3 receptors) and inhibitory receptors (alpha 2-adrenoceptors, histamine H3, GABAA- and GABAB-, A2 and P2y alpha purine and 5-HT4 receptors as well as receptors for vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase stimulating peptide (PACAP) and somatostatin) have been shown to be involved in the control of 5-HT release from the ECs.

Animals↗
PubMed1995

Modulation of noradrenaline release in rat isolated stomach by prostanoids, but not by histaminergic mechanisms.

Several gastric functions are modulated by the sympathetic nervous system, but local mechanisms involved in the control of noradrenaline release are largely unknown. Overflow of endogenous noradrenaline was studied from isolated rat stomach incubated in Ussing chambers allowing the separate determination of mucosal and serosal overflow. Spontaneous noradrenaline overflow was similar at the mucosal and serosal side, but electrical field stimulation caused a frequency-dependent increase in noradrenaline overflow selectively at the serosal side. Evoked noradrenaline overflow was blocked by tetrodotoxin, not affected by indometacin and markedly enhanced (by about 250%) by yohimbine. In the presence of indometacin and yohimbine, sulprostone (an agonist at EP1/EP3 receptors) and misoprostol (an agonist at EP2/EP3 receptors) reduced the noradrenaline overflow evoked by stimulation at 3 Hz maximally by about 80% (EC50: 6 nmol/l and 11 nmol/l, respectively). The EP1 receptor selective antagonist AH 6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid) did not antagonize the inhibition by sulprostone. Noradrenaline overflow evoked by stimulation at 1 Hz and 3 Hz was increased by scopolamine by about 50% and almost completely inhibited by oxotremorine. Neither, histamine nor the H3 receptor selective agonist (R)-alpha-methyl-histamine, nor the H1, H2 and H3 selective receptor antagonists mepyramine, cimetidine and thioperamide significantly affected noradrenaline overflow evoked by stimulation at 1 Hz or 3 Hz. In conclusion, impulse-induced noradrenaline release in the rat stomach is controlled by multiple presynaptic mechanisms involving alpha 2-adrenergic autoreceptors, EP3 prostanoid and muscarine heteroreceptors, whereas histaminergic mechanisms do not appear to be significant.

Abortifacient Agents, Nonsteroidal↗
PubMed1994

Characterization of histamine H3 receptors inhibiting 5-HT release from porcine enterochromaffin cells: further evidence for H3 receptor heterogeneity.

The nature of the histamine receptor mediating inhibition of 5-HT release was investigated in strips of the porcine small intestine by investigating the effects of histamine ligands on the overflow of endogenous 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA). The overflow was measured by HPLC, combined with electrochemical detection and represents calcium-sensitive 5-HT release from enterochromaffin cells, as reported previously. The histamine H3 receptor selective agonists (R)-alpha-methyl-histamine and imetit inhibited the overflow of 5-HT maximally by 50-60%, with EC50 values of 48 and 3.2 nmol/l, respectively. Effects on 5-HT overflow were always accompanied by similar effects on the overflow of 5-HIAA. Thioperamide (100 nmol/l) shifted the concentration response curve of (R)-alpha-methyl-histamine to the right (pKB value 8.38). The inhibitory effect of 1 mumol/l (R)-alpha-methyl-histamine was antagonized in a concentration-dependent manner by thioperamide (IC50: 65 nmol/l) and dimaprit (IC50: 8.6 mumol/l); however, the effect of (R)-alpha-methyl-histamine was weakly antagonized by burimamide (by 38% at 100 mumol/l) and not significantly affected by other H3 receptor antagonists, such as impromidine, betahistine and phenyl-butanoyl-histamine (each up to 100 mumol/l). In conclusion, H3 receptors mediating inhibition of 5-HT release from porcine enterochromaffin cells have a particular pharmacological profile indicating that heterogeneity of H3 receptors may exist. The data suggest that histamine H3 receptors modulating 5-HT release in pig small intestine do not belong to either H3A or H3B receptors as defined in rat tissue.

Animals↗
PubMed1993

Tissue-specific regulation of bovine heart cytochrome-c oxidase activity by ADP via interaction with subunit VIa.

The activity of reconstituted cytochrome-c oxidase (EC 1.9.3.1) from bovine heart is stimulated by intraliposomal ADP but not by NaCl of the same ionic strength. A monoclonal antibody which reacts with subunits VIa-H (heart-type) and VIc, due to the evolutionary relationship between these subunits, also stimulates the activity of the enzyme from bovine heart but not from bovine liver. The antibody induces a conformational change in the heart enzyme but not in the liver enzyme, as shown by the visible difference spectrum. Preincubation of heart cytochrome-c oxidase with the antibody prevents stimulation of activity by intraliposomal ADP after reconstitution in liposomes. Reconstituted liver cytochrome c oxidase is not stimulated by intraliposomal ADP. The data suggest tissue-specific regulation of the activity of cytochrome-c oxidase by ADP via interaction with the matrix domain of subunit VIa-H.

Adenosine Diphosphate↗
PubMed1993

Ferricytochrome c induces monophasic kinetics of ferrocytochrome c oxidation in cytochrome c oxidase.

The kinetics of ferrocytochrome c oxidation by reconstituted cytochrome c oxidase (COX) from bovine heart was followed by a spectrophotometric method, using on-line data collection and subsequent calculation of reaction rates from a function fitted to the progress curve. When reaction rates were calculated at increasing reaction times, the multiphasic kinetics of ferrocytochrome c oxidation gradually changed into monophasic Michaelis-Menten kinetics. The same phenomenon was observed when ferrocytochrome c oxidation was followed in the presence of increasing amounts of ferricytochrome c. From these results we conclude that ferricytochrome c shifts the multiphasic kinetics of ferrocytochrome c oxidation by COX into monophasic kinetics, comparable to high ionic strength conditions. Furthermore, we show that ferricytochrome c inhibits the "high affinity phase" of ferrocytochrome c oxidation in an apparently competitive way, while inhibition of the "low affinity phase" is noncompetitive. These findings are consistent with a "regulatory site model" where both the catalytic and the regulatory site bind ferro- as well as ferricytochrome c.

Animals↗