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Biomedical subjects

G Adam

Publications and source records attributed to G Adam.

At least 91 records · Page 5Linked to original sources
PubMed2002

[Formation of portal venous collaterals after ligation of the portal vein for induction of liver regeneration].

PURPOSE: Unilateral occlusion of the portal vein induces contralateral lobar hypertrophy - in contrast to complete portal vein occlusion which will result in a cavernous transformation. The impact of the formation of collaterals in partial portal vein occlusion is not sufficiently known. The lobar-hypertrophy- phenomenon is in clinical use for several years to induce iatrogenic liver growth to enable extended resections. After portal vein ligation in patients prior to extended hepatic resections, we noticed a perfusion of the formerly occluded side on CT. Using the well-established mini pig model, we were interested whether portal collaterals are formed as cause of the reperfusion. Ex-situ angiograms of the liver were used for the depiction of collaterals. MATERIALS AND METHODS: Using a median laparotomy as access for preparation of the hepatoduodenal ligament, a proximal left portal vein ligation was performed in eight mini pigs under general anesthesia. The total arrest of the portal blood flow (except in segments VI and VII) was documented by duplex ultrasound. After 4 weeks, all pigs were sacrificed and the weight of the ligated liver segments and non-ligated liver segments was measured and compared to a sham group (n = 5). After insertion of a guiding sheath, an ex-situ DSA of the portal vein was acquired. RESULTS: Compared with the sham group, the liver weight increased by 60 % (23 - 99 %, std. dev. 30 %) in segments VI and VII. Atrophy of the ligated segments was signified by a weight loss of 10 % (standard deviation 15 %). The ex-situ angiograms revealed a uniform pattern of collaterals with subsequent complete total recanalization of the formerly occluded portal vein distal from the ligation. The collaterals reduced the portal venous flow rate. CONCLUSION: After portal vein ligation, uniform collateralization results in recanalization of the occluded portal vein. The extent of the collaterals exceeds the known cavernous transformation. The increase in liver volume is not restrained by the formation of collaterals.

Aged↗
PubMed2002

[The role of MRI for the evaluation of atrial septal defects before and after percutaneous occlusion with the amplatzer septal occluder(R)].

PURPOSE: Evaluation of morphologic and functional MRI of atrial septal defects (ASD) before and after percutaneous occlusion with the Amplatzer Septal Occluder (AOC). Comparison of MRI with transesophageal echocardiography (TEE), balloon measurement (IVBM) and cardiac catheterization with shunt quantification (CCSQ). MATERIALS AND METHODS: Twenty patients with ASD were examined before and three months after AOC implantation. ECG-triggered, breath-hold T1-weighted Turbo Spin Echo Segmented FLASH 2D and dynamic turbo-FLASH-GRE sequences after application of 0.2 mmol gadolinium DTPA per kg body weight were obtained in a 1.5 T MRI system. Defect size, and distance to coronal sinus (CS) and right upper pulmonary vein (RUPV) were determined for pre-interventional planning, and the AOC size was measured quantitatively for post-interventional follow-up. The shunts were evaluated qualitatively (occurrence of jets), semiquantitatively (jet length, turbulence square product) and quantitatively (flow measurement in the thoracic aorta and in the left and right pulmonary arteries). RESULTS: The average size of the ASD measured by MRI was 17.6 mm (11 - 24.8 mm) in the axial view, 15.9 mm (10.8 - 28.9 mm) in the sagittal view and 16.4 mm (12.1 - 24.8 mm) in the short axis view. In comparison, the average defect size was 15 mm (8 - 24 mm) by TEE and 20 mm (13 - 27 mm) by IVBM. The average distance to the RUPV was 17 mm (9.6 - 21.9 mm) and to the CS 11.2 mm (5 - 17 mm). The AOC was visualized with only minimal artifacts. Qualitative analysis of the MRI findings revealed an occurrence of jets in 17/20 patients. Semiquantitative analysis documented a high correlation for jet length and square product of the turbulence to defect size r = 0.81 resp. r = 0.82. Mean QP/QS-ratio measured by MR-volumetry was 1.6 +/- 0.29 and by MR-flow 1.6 +/- 0.26. The corresponding measurements were 1.7 +/- 0.3 for TEE and 1.5 +/- 0.5 for CCSQ. In comparison to TEE, the correlation coefficient was r = 0.96 for MR-volumetry and r = 0.85 for MR-flow measurement. CONCLUSION: MRI is found to be a valuable diagnostic method for pre-interventional planning and post-interventional follow-up of atrial septal defects occluded by the Amplatzer septal occluder.

Adult↗
PubMed2002

[Evaluation of TSE- and T1-3D-GRE-sequences for focal cartilage lesions in vitro in comparison to ultrahigh resolution multi-slice CT].

PURPOSE: Evaluation of TSE- and T 1 -3D-GRE-sequences for focal cartilage lesions in vitro in comparison to ultrahigh resolution multi-slice CT. MATERIALS AND METHODS: Forty artificial cartilage lesions in ten bovine patellae were immersed in a solution of iodinated contrast medium and assessed with ultrahigh resolution multi-slice CT. Fat-suppressed TSE images with intermediate- and T 2 -weighting at a slice thickness of 2, 3 and 4 mm as well as fat-suppressed T 1 -weighted 3D-FLASH images with an effective slice thickness of 1, 2 and 3 mm were acquired at 1.5 T. After adding Gd-DTPA to the saline solution containing the patellae, the T 1 -weighted 3D-FLASH imaging was repeated. RESULTS: All cartilage lesions were visualised and graded with ultrahigh resolution multi-slice CT. The TSE images had a higher sensitivity and a higher inter- and intraobserver kappa compared to the FLASH-sequences (TSE: 70 - 95 %; 0.82 - 0.83; 0.85 - 0.9; FLASH: 57.5 - 85 %; 0.53 - 0.72; 0.73 - 0.82, respectively). An increase in slice thickness decreased the sensitivity, whereby deep lesions were even reliably depicted on TSE images at a slice thickness of 3 and 4 mm. Adding Gd-DTPA to the saline solution increased the sensitivity by 10 % with no detectable advantage over the T 2 -weighted TSE images. CONCLUSION: TSE sequences and application of Gd-DTPA seemed to be superior to T 1 -weighted 3D-FLASH sequences without Gd-DTPA in the detection of focal cartilage lesions. The ultrahigh resolution multi-slice CT can serve as in vitro reference standard for focal cartilage lesions.

Animals↗
PubMed2002

[MRI in postoperative assessment of univentricular heart disease: correlation with echocardiography and angiography].

PURPOSE: To determine the value of MRI in the postoperative evaluation of a singular ventricle compared to echocardiography and cardiac catheterization. MATERIALS AND METHODS: Thirty-one patients (range: 6 months to 30 years) with a functional single ventricle following palliative corrective operations. Five patients had a Blalock-Taussig-Shunt, 8 patients a Glenn-Anastomosis and 18 a cavopulmonary shunt (6 with classic Fontan-Circulation, 12 with modified cavopulmonary anastomosis). The results in terms of postoperative morphologic changes were compared to percutaneous echocardiography (31/31) and cardiac catheterization (6/31). RESULTS: Echocardiography, which was performed on all patients, could not visualize the entire length of the tunnel, the Glenn-Anastomosis or the central pulmonary arteries in 70 % of the patients due to an inadequate acoustic window. MRI was able to show the entire tunnel in 11/12 patients and the central pulmonary arteries in 30/31 patients. The exact anatomy was seen in all 6 patients undergoing cardiac catheterization. CONCLUSION: MRI is useful in the postoperative evaluation of a functionally single ventricle. It is superior to echocardiography. Cardiac catheterization should be reserved for patients with inconclusive MRI findings.

Adolescent↗
PubMed2001

MR-guided percutaneous cryotherapy of the liver: in vivo evaluation with histologic correlation in an animal model.

The purpose of this study was to evaluate the feasibility of MR-guided percutaneous cryotherapy of the porcine liver and to correlate the resulting tissue necrosis with MR imaging and histology. Using an MR-compatible, argon-based cryotherapy system (CryoHit; Galil Medical Ltd., Israel) with 2- and 3-mm diameter tapered cryotherapy probes, MR-guided percutaneous cryotherapy was performed in seven pigs (mean body weight, 40 kg) under general anesthesia in a short-bore magnet (1.5 T ACS NT; Philips, The Netherlands) using an ultrafast T2-weighted single-shot LoLo TSE sequence and a T1-weighted gradient-echo sequence. The frozen liver tissue was depicted accurately on fast T2- and T1-weighted sequences, providing precise delineation of the ablated tissue volume. On follow-up postcontrast MR controls, the cryolesions appeared avascular. They decreased in size compared with the initially frozen volume down to 70% at a 2-week follow-up. Histologically, a coagulation necrosis with a close correlation to the MR follow-up examinations was objectified. No cryotherapy-related complications occurred. J. Magn. Reson. Imaging 2001;13:50-56.

Animals↗
PubMed2001

Comparison of aerosolized gadoteridol and gadopentetate dimeglumine for magnetic resonance ventilation imaging of the lung.

The purpose of this study was to compare aerosolized gadoteridol and gadopentetate dimeglumine in regard to homogeneity of aerosol distribution and relative pulmonary signal intensity (SI) changes after a 10-min mechanical ventilation period. Twenty experimental procedures were performed in 10 intubated domestic pigs that were mechanically aerosolized with the nebulized contrast medium. Images were obtained by using a respiratory-gated T(1)-weighted TSE sequence. Pulmonary SI increase for the right and left lung was 26% +/- 25% and 25% +/- 12%, respectively, for gadopentetate dimeglumine, and 45% +/- 12% and 43% +/- 10%, respectively, for gadoteridol. Aerosol distribution was rated homogeneous in all cases by two readers. It is concluded that both contrast agents in aerosolized form are capable of depicting pulmonary ventilation in healthy animals with lung capacities comparable to those of humans. SI differences between gadoteridol and gadopentetate dimeglumine are explained by their considerable difference in viscosity.

Aerosols↗
PubMed2001

Pharmacological properties of native metabotropic glutamate receptors in freshly dissociated Golgi cells of the rat cerebellum.

We have examined the pharmacological properties of native metabotropic glutamate (mGlu) receptors in freshly isolated rat cerebellar Golgi cells using the whole-cell configuration of the patch-clamp technique. Group II mGlu receptor agonists inhibited voltage-gated Ca(2+) channels (VGCC) currents in a reversible and concentration-dependent manner with a rank order of potency being LY354740> DCG-IV > L-CCG-I > glutamate >>1S,3R-ACPD > NAAG. The maximum degree of inhibition obtained was similar for all drugs tested, saturating at about 33-41%, except for NAAG that had a non saturating effect of 50% at 1mM. Two novel group II mGlu receptor antagonists, LY341495 and Ro 65-3479, reversed VGCC current inhibition by LY354740 with pK(B) values of 7.0 and 6.3, respectively. In a subpopulation of Golgi cells, the antagonistic effect of LY341495 was only partial, suggesting a remaining effect of group I mGlu receptors. This was confirmed by experiments with S-DHPG, a selective group I mGlu receptor agonist. These experiments suggest that Golgi cells of the cerebellum express group II mGlu receptors that couple to the inhibition of VGCCs. Therefore, inhibition of VGCCs in cerebellar Golgi cells is a useful model system to evaluate novel group II mGlu receptor ligands.

Animals↗
PubMed2001

Influence of the selective ORL1 receptor agonist, Ro64-6198, on rodent neurological function.

Identification of synthetic agonists and antagonists at orphan receptors represents an important step for understanding their physiological function and therapeutic potential. Accordingly, we have recently described a non-peptide agonist at the opioid receptor like (ORL1) receptor (1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one (Ro64-6198; Jenck et al., PNAS 94 (2000) 4938; Wichmann et al., Eur. J. Med. Chem. 35 (2000) 839). We have investigated the effects of this compound in various tests of rodent neurological function, utilising ORL1 knockout mice to examine the pharmacological specificity of Ro64-6198. In male C57BL/6J mice, effects on balance and motor co-ordination were detected following low doses (0.3-1mg/kg IP) of Ro64-6198. At higher doses (1-3mg/kg IP), effects on swim behaviour and hypothermia was observed. At 10mg/kg, each effect became more profound and a severe neurological disturbance appeared, including loss of righting reflex. These effects of Ro64-6198 (10mg/kg IP) were absent in ORL1 receptor knockout mice. In male, hooded Lister rats, Ro64-6198 (6-10mg/kg IP), produced some disturbance of neurological function, including hypoactivity, rotarod performance, grip strength and mild hypothermia. An impairment of food responding under a variable interval (VI) 20s schedule of reinforcement was noted at 3mg/kg. These results confirm Ro64-6198 to be a highly selective pharmacological tool to investigate ORL1 receptor function in vivo and, furthermore, that activation of this receptor is accompanied by a variety of effects on neurological function.

Animals↗
PubMed2001

Guaiane dimers from Xylopia vielana.

From the leaves of Xylopia vielana (Annonaceae) the three dimeric guaianes vielanin A-C were isolated and structurally elucidated by mass and NMR spectroscopy as 1-3. The structure of 1 contains a bridged ring system formed probably via a Diels-Alder reaction of two different guaiane monomers. Compounds 2 and 3 represent symmetric cyclobutanes formally generated from two equal guaiane moieties by [2 + 2] cycloaddition.

Catechin↗
PubMed2001

Furanocoumarins from Dorstenia gigas.

A series of linear and angular prenylated furanocoumarins and a benzofuran derivative were isolated from leaves and twigs of Dorstenia gigas (Moraceae), a plant occurring endemically on Socotra Island (Yemen). The structures were elucidated by spectroscopic methods (NMR, MS, UV) and chemical derivatization.

Benzofurans↗
PubMed2001

[Differentiation of serous and purulent fluids in vitro and in vivo by means of diffusion-weighted MRI].

AIM: The aim of this study was to test the feasibility for differentiation of serous fluid collections and abscess fluid with diffusion-weighted imaging and to compare three different diffusion sequences. MATERIAL AND METHODS: Thirteen puncture samples (6 serous, 7 purulent) and 19 patients with either serous fluid collections (n = 12) or abscesses (n = 7) were examined with diffusion-weighted spin-echo (SE), stimulated-echo (STE), and fatsuppressed SE (SE-SPIR) sequences. For in vitro studies 4 different b-factors (0, 87, 355, 798 s/mm2 in SE and SE-SPIR and 0, 51, 204, 460 s/mm2 in STE) were chosen and the apparent diffusion coefficient (ADC) was calculated. For in vivo measurements identical sequences with two b-factors (0.598 s/mm2 in SE and SE-SPIR and 0.360 s/mm2 in STE) were applied and the normalized signal attenuation was calculated. A navigator-echo technique and peripheral pulse triggering was used for motion artifact reduction. RESULTS: The in vitro study yielded an ADC of serous fluid, which was close to that of free water, whereas for purulent fluid a significantly lower ADC was calculated. During in vivo examinations, serous fluids showed a strong signal attenuation (down to 22-32% of basic value) compared to a minor signal attenuation in purulent fluids (down to 86-94% of basic value) (p < 0.05). CONCLUSIONS: In summary, with all three investigated diffusion schemes serous and purulent fluids can be clearly differentiated.

Abscess↗
PubMed2001

[MRI first-pass myocardial perfusion in patients undergoing percutaneous myocardial laser revascularization].

PURPOSE: Evaluation of MRI first-pass myocardial perfusion pre- and post-percutaneous myocardial laser revascularisation (PMR). PATIENTS AND METHODS: MRI was performed in 10 patients with coronary heart disease grade III-IV, 1-4 days prior to PMR, as well as 1-5 days and 6 months after PMR. Contrast enhanced (0.1 ml/kgBw; 4 ml/s) "first-pass" MRI imaging was obtained by breath-hold, ECG-triggered, multislice Turbo-FLASH GRE. For quantitative analysis the absolute and percentual signal-to-noise (S/N)-measurements were calculated. Positron emission tomography (PET) was regarded as the gold standard for myocardial perfusion. RESULTS: The mean values of absolute and % S/N increase revealed no statistical difference between pre- and immediately post-PMR imaging. 6 months following PMR both values were significantly elevated (14.1 vs. 24.4 and 127 vs. 176; p = 0.03 and p = 0.01). However, the non-treated myocardial segments revealed a similar S/N pattern. Intraindividual analysis showed a significant S/N increase post PMR in one patient, and in additional 4 patients 6 months later. PET revealed increased myocardial perfusion in only two patients. Following PMR 5/10 patients experienced a significant reduction of chest pain equivalent to two CCS grades. Two of these had significant S/N elevations but no evidence of increased perfusion by PET. CONCLUSION: S/N first-pass calculations following PMR do not correlate well with the true situation of myocardial perfusion. They seem to be more closely associated with other histological phenomena and possible explanations for the improved clinical symptomatology.

Aged↗
PubMed2001

Mechanical delivery of aerosolized gadolinium-DTPA for pulmonary ventilation assessment in MR imaging.

RATIONALE AND OBJECTIVES: To evaluate a new technique with mechanical administration of aerosolized gadolinium (Gd)-DTPA for MR visualization of lung ventilation. METHODS: Ten experimental procedures were performed in six domestic pigs. Gd-DTPA was aerosolized by a small-particle generator. The intubated animals were mechanically aerosolized with the nebulized contrast agent and studied on a 1.5-T MR imager. Respiratory gated T1-weighted turbo spin-echo images were obtained before, during, and after contrast administration. Pulmonary signal intensity (SI) changes were calculated for corresponding regions of both lungs. Homogeneity of aerosol distribution was graded independently by two radiologists. RESULTS: To achieve a comparable SI increase as attained in previous trials that used manual aerosol ventilation, a ventilation period of 20 minutes (formerly 30 minutes) was sufficient. Mean SI changes of 116% were observed after that duration. Contrast delivery was rated evenly distributed in all cases by the reviewers. CONCLUSIONS: The feasibility of applying Gd-DTPA as a contrast agent to demonstrate pulmonary ventilation in large animals has been described before. The results of this refined technique substantiate the potential of Gd-based ventilation MR imaging by improving aerosol distribution and shortening the nebulization duration in the healthy lung.

Aerosols↗
PubMed2001

Identification of essential residues involved in the glutamate binding pocket of the group II metabotropic glutamate receptor.

Metabotropic glutamate (mGlu) receptors are a family of G-protein-coupled receptors that play central roles as modulators of both glutamatergic and other major neurotransmitter systems in CNS. Using molecular modeling, site-directed mutagenesis, [(3)H]LY354740 binding, [(35)S]GTPgammaS binding, and activation of GIRK current, we have been able to identify residues crucial for the binding of LY354740 and glutamate to rat mGlu2 receptors. Several of the crucial residues located in the binding site (Arg-57, Tyr-144, Tyr-216, Asp-295) have not been identified previously. We propose that the gamma-carboxyl group of LY354740 forms H-bonds to Arg-57, whereas the alpha-carboxyl group forms an H-bond with the hydroxyl group of Ser-145. The alpha-amino group of LY354740 forms H-bonds to Asp-295 and to the side-chain hydroxyl group of Thr-168. In addition, Tyr-144 may establish a hydrophobic (C-H/pi)-interaction with the bicyclo-hexane ring of LY354740. Furthermore, the mutation of residues Ser-148 and Arg-183, which are too remote for a direct interaction, affected the ligand affinity dramatically. These results suggest that Ser-148 and Arg-183 may be important for the 3D structure and/or are involved in closure of the domain. Finally, Asp-146, which is also remote from the binding site, was shown to be involved in the differential binding affinity of [(3)H]LY354740 for mGlu2 versus mGlu3 receptors. All the mGlu receptors except mGlu2 are activated by Ca(2+) and have serine instead of aspartic acid at this position, which suggests a critical role of this aspartic acid residue in the binding properties of this unique receptor.

Amino Acids↗
PubMed2001

Pneumatosis intestinalis following cytotoxic or immunosuppressive treatment.

Pneumatosis intestinalis (PI) is an uncommon condition characterized by the presence of gas within the bowel wall. We describe 5 cases of PI that occurred after cytotoxic or immunosuppressive treatment for hematological disorders. All patients were neutropenic shortly before or at the time of diagnosis of PI, but did not show specific symptoms. The diagnosis was made by conventional X-ray and confirmed by abdominal computed tomography. Since there were no signs of secondary complications such as peritonitis, ischemia, or perforation, conservative treatment with broad-spectrum antibiotics and parenteral nutrition was initiated. All patients but 1 achieved complete resolution of PI after recovery from myelosuppression. Benign pneumoperitoneum due to PI should be considered in the differential diagnosis of free intra-abdominal air after chemotherapeutic or immunosuppressive therapy. It can be managed successfully by conservative treatment in the absence of secondary complications, if there is recovery of myelopoiesis.

Adult↗
PubMed2001

Allele-specific in situ hybridization (ASISH).

An unexpected outcome of the diploid genome is that evolutionary strategies have evolved to express only one of the alleles (1). The rapidly expanding list of genes that are expressed monoallelically fall into three main categories: random inactivation, allelic exclusion, and genomic imprinting. These categories are distinguished by whether the expressed and inactivated alleles are maintained from one cell division to the next (random inactivation occurs with each cell division, compared to stable propagation through subsequent cell divisions as seen for allelic exclusion and genomic imprinting) and whether allele inactivation or expression is determined by parent of origin of inheritance (this differentiates allelic exclusion from genomic imprinting). Genomically imprinted genes are currently more numerous than members of the other categories. This fact is likely to reflect that the persistent (in)activation of one allele in a parent of origin-specific manner has facilitated the detection of monoallelic expression patterns in RNA extracted from homogenized tissue. This crude approach does not take into account, however, different imprinted states within a tissue, or, indeed, random allelic (in)activation. It is not surprising, therefore, that well-known genes, such as Il2 (2), were only recently found to be monoallelically expressed in a random manner (1).

Alleles↗
PubMed2001

Diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration of the vertebral body.

OBJECTIVE: The aim of this study was to investigate diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration with and without accompanying fracture. SUBJECTS AND METHODS: In 10 volunteers, diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences were optimized on a clinical 1.5-T scanner. In 34 patients, MR imaging with and without diffusion-sensitizing gradients (b = 598 sec/mm(2) in spin-echo and fat-suppressed spin-echo, b = 360 sec/mm(2) in stimulated-echo) was performed. Thirty-five lesions were analyzed, with 18 caused by acute (< or =10 days old) osteoporotic or traumatic fractures and 17 caused by untreated malignant vertebral infiltration including nine fractures. Signal attenuation in diffusion-weighted images and contrast-to-noise ratio were calculated. The diffusion-weighted images were analyzed by two radiologists. RESULTS: Images from three of 34 patients were excluded because of motion artifact. In osteoporotic and traumatic fractures, a strong signal attenuation of bone marrow edema was seen. In contrast to this, malignant-tumor infiltration caused only minor signal attenuation (p < 0.05), independent of accompanying pathologic fracture. All sequences showed identical changes of signal intensities. In four patients, initial diagnosis was changed by the findings in the diffusion-weighted images. CONCLUSION: Diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences are equally suitable for imaging of the spine. Calculation of signal attenuation and observation of signal characteristics allowed differentiation of benign fracture edema and tumor infiltration and provided excellent distinction between benign and malignant vertebral fractures in our series.

Adult↗