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Biomedical subjects

M Langer

Publications and source records attributed to M Langer.

At least 73 records · Page 4Linked to original sources
PubMed2001

Gadolinium-enhanced elliptically reordered three-dimensional MR angiography in the assessment of hand vascularization before radial artery harvest for coronary artery bypass grafting: first experience.

RATIONALE AND OBJECTIVES: To assess the suitability of contrast-enhanced magnetic resonance angiography (MRA) in the preoperative evaluation of hand vasculature in potential candidates for radial artery bypass grafting. METHODS: In 21 patients, gadobenate dimeglumine-enhanced, three-dimensional gradient-echo sequences of both hands were performed, as well as a Doppler ultrasound study with radial artery compression. Doppler findings were correlated with MRA, focusing on the assessment of anastomoses between the vascular bed of the ulnar and radial arteries. RESULTS: One individual had to be excluded because of accidentally disclosed metal foreign bodies. Sufficient depiction of the hand vasculature was achieved in the remainder. Seventeen patients had evidence of adequate collateral flow between the ulnar and radial artery supply on Doppler ultrasound. Three patients exhibited inadequate collateral flow, with angiographic signs of vessel occlusion or missing collaterals between the palmar arches. Two patients presented with stenosis or occlusion of the radial artery. Magnetic resonance angiograms displayed great variations in hand vasculature and collateral formation, with no mismatch compared with Doppler ultrasound results. CONCLUSIONS: Contrast-enhanced MRA displays vascularization of the hand in detail and supplies ultrasound flow measurements for radial artery harvest, with high-resolution angiographic data about possible vessel variations and the presence of anastomoses between the radial or ulnar artery supply.

Adult↗
PubMed2001

Improved leaf sequencing reduces segments or monitor units needed to deliver IMRT using multileaf collimators.

Leaf sequencing algorithms may use an unnecessary number of monitor units or segments to generate intensity maps for delivery of intensity modulated radiotherapy (IMRT) using multiple static fields. An integer algorithm was devised to generate a sequence with the fewest possible segments when the minimum number of monitor units are used. Special hardware related restrictions on leaf motion can be incorporated. The algorithm was tested using a benchmark map from the literature and clinical examples. Results were compared to sequences given by the routine of Bortfeld that minimizes monitor units by treating each row independently, and the areal or reducing routines that use fewer segments at the price of more monitor units. The Bortfeld algorithm used on average 58% more segments than provided by the integer algorithm with bidirectional motion and 32% more segments than did an integer algorithm admitting only unidirectional sequences. The areal algorithm used 48% more monitor units and the reducing algorithm used 23% more monitor units than did the bidirectional integer algorithm, while the areal and reducing algorithms used 23% more segments than did the integer algorithm. Improved leaf sequencing algorithms can allow more efficient delivery of static field IMRT. The integer algorithm demonstrates the efficiencies possible with an improved routine and opens a new avenue for development.

Algorithms↗
PubMed2001

Peptides as carrier for tumor diagnosis and treatment.

The specific binding of peptides to their receptors can be used to meet the key requirement in tumor targeting: selective addressing of neoplasm. Because of their small size, peptides exhibit faster blood clearance and higher target-to-background ratios compared to macromolecular compounds. In radiopharmacy, these advantages have been attended, and radiolabelled receptor-binding peptides have emerged as a new class of radiopharmaceuticals. Over the last years, nuclear medicine has evaluated various peptides for tumor scintigraphy. The challenge is to label bioactive peptides without affecting their receptor binding properties. Size, plasma protein binding, lipophilicity and sensitivity to proteolysis are to be considered, as well as biodistribution, metabolism and excretion characteristics. The variety of experiences gained in the development of peptide analogues and radiolabelling methods, and latest results from in vitro, in vivo and clinical studies will be presented. The tumor receptor-targeting approach with peptides can be extended to cancer chemotherapy. One of the major problems in classic chemotherapy is the non-specific toxicity of most anticancer agents against normal cells. Coupling cytotoxic drugs to macromolecular carriers has been shown to be a promising approach for efficient drug targeting. In the past few years, peptides were introduced as carriers. Different conjugates, composed of a peptide carrier and a cytotoxic moiety, have been investigated so far. Anticancer drugs were coupled to analogues of luteinizing hormone-releasing hormone, bombesin, somatostatin and neuropeptide Y. Suitable candidates maintained their binding affinity and could preserve the cytotoxic activity in vitro and in vivo, resulting in a peptide-mediated selective chemotherapy.

Animals↗
PubMed2001

The knee joint in early juvenile idiopathic arthritis. An ROC study for evaluating the diagnostic accuracy of contrast-enhanced MR imaging.

PURPOSE: Diagnosis of juvenile idiopathic arthritis (JIA) remains difficult due to unspecific clinical and laboratory findings, especially in early stages of the disease. The purpose of our study was to determine the sensitivity and specificity of MR imaging in diagnosing JIA of the knee joints. MATERIAL AND METHODS: Forty children (3-17 years old) clinically diagnosed with JIA (follow-up > 1 year) of a knee joint and a control group of 40 children with painful knee joints (MR diagnosis: bone bruise of the knee (n = 7), normal knee joint (n = 12), osteomyelitis (n = 6), septic arthritis (n = 2), bone tumor (n = 7) and miscellaneous bone lesions (n = 6)) were examined using a 1.5 T MR unit. T1-weighted spin-echo (SE), T2-weighted fast SE, contrast-enhanced T1-weighted SE and 2D gradient echo sequences were performed. The receiver operating characteristic (ROC) curves evaluation was conducted by 5 independent radiologists. RESULTS: The positive criteria for diagnosing JIA were joint effusions (n = 40), contrast-enhancing synovitis (n = 39), cartilage lesions (n = 15), subchondral erosions and bony destruction (n = 1). Sensitivity and specificity were 93.5% and 92.5%, respectively. Both cases of septic arthritis were misdiagnosed as JIA by all radiologists. CONCLUSION: Contrast-enhanced MR imaging seems to be a highly sensitive tool in establishing the diagnosis of JIA.

Adolescent↗
PubMed2000

The first selective agonist for the neuropeptide YY5 receptor increases food intake in rats.

The first Y(5) receptor-selective analog of neuropeptide Y (NPY), [Ala(31),Aib(32)]NPY, has been developed and biologically characterized. Using competition binding assays on cell lines that express different Y receptors, we determined the affinity of this analog to be 6 nm at the human Y(5) receptor, >500 nm at the Y(1) and Y(2) receptors, and >1000 nm at the Y(4) receptor. Activity studies performed in vitro using a cAMP enzyme immunoassay, and in vivo using food intake studies in rats, showed that the peptide acted as an agonist. Further peptides obtained by the combination of the Ala(31)-Aib(32) motif with chimeric peptides containing segments of NPY and pancreatic polypeptide displayed the same selectivity and even higher affinity (up to 0.2 nm) for the Y(5) receptor. In vivo administration of the new Y(5) receptor-selective agonists significantly stimulated feeding in rats. The NMR solution structures of NPY and [Ala(31),Aib(32)]NPY showed a different conformation in the C-terminal region, where the alpha-helix of NPY was substituted by a more flexible, 3(10)-helical turn structure.

Amino Acid Motifs↗
PubMed2000

Cytotoxic activity of recombinant bFGF-rViscumin fusion proteins.

A fusion protein (bFGF-rMLA), containing the mitogen basic fibroblast growth factor (bFGF) and the cytotoxic component of rViscumin (recombinant mistletoe lectin), the enzymatic A-chain (rMLA), was expressed in Escherichia coli, purified, and functionally characterized. bFGF-rMLA is cytotoxic for mouse B16 melanoma cells expressing the FGF receptor with an IC(50) value of approximately 1 nM. rMLA shows no significant effect on the viability of the B16 cells up to a concentration of 141 nM. Additionally, bFGF-rMLA was associated with the rViscumin B-chain (rMLB) in an in vitro folding procedure. The IC(50) value of bFGF-rMLA/rMLB to B16 cells in the presence of lactose-to block rMLB lectin activity-was 134 pM. Thus, it was possible to enhance the efficacy of a rViscumin A-chain mitotoxin through addition of rMLB. We conclude that rViscumin fusion proteins may be generally applicable for the receptor-specific inactivation of target cells and point out their potential in drug development.

Animals↗
PubMed2000

[Peptic ulcer in the elderly--endoscopy in suspected ulcer. Therapy always includes proton pump inhibitor].

In the elderly patient, peptic ulcer disease is associated with increased morbidity and mortality. Abdominal pain is often absent, and the first sign is blood in the stools. The major risk factors are infection with Helicobacter pylori and the use of non-steroidal antiinflammatory drugs (NSAIDs). Endoscopic and medical treatment of peptic ulcer is independent of the age. The use of proton pump inhibitors is the treatment of choice. In the event of an infection with H. pylori, eradication treatment is usually carried out. Currently, however, H. pylori eradication is not recommended in patients with NSAID-associated ulcers; if possible, the NSAIDs should be discontinued. The development of a new generation of NSAIDs holds out the promise of a marked reduction in gastrointestinal side effects.

Aged↗
PubMed2000

Assessment of arterial blood flow characteristics in normal and atherosclerotic vessels with the fast Fourier flow method.

The purpose of this study was to scrutinize the ability of magnetic resonance imaging (MRI)-performed measurements to compare arterial flow patterns in patients with peripheral arterial occlusive disease (PAOD), healthy volunteers (HV) and endurance athletes (EA). MRI blood flow data were partially repeated with Doppler ultrasound (DUS) with a view to a methodical comparison. Additionally, pulse wave velocity was assessed with the MUFF technique. For this purpose, MRI-performed flow measurements were performed in the common femoral artery in 21 patients with PAOD, in 34 HV and in 12 EA. The analysis included maximum flow velocities (MFV), velocity/time profile (VTP), pulse wave velocity (Vpulse), and vessel diameter (VD). In addition, MFV and VD were observed by DUS in most individuals. The results revealed a significant change regarding arterial blood flow characteristics in patients compared with HV and EA, with respect to the span between the peak positive and negative blood flow velocity in the femoral artery. The pulse wave velocity in patients was markedly elevated compared with healthy individuals. Furthermore, a complete, characteristic change in the VTP could be observed in patients. The methodical comparison between DUS and MRI showed a good correlation. Multi-slice Fourier flow data have indicated markedly increased pulse wave velocity in PAOD patients. Changes in the arterial blood flow can be clearly observed with MRI. In the future, this might offer a noninvasive possibility not only for the evaluation of the stage of the disease, but also for the detection of early, pre-clinical stages of atherosclerosis.

Adult↗
PubMed2000

[A new technique of subdermal flap dissection for reconstruction of the ala of the nose].

There are different techniques for reconstruction of the ala of the nose. Nasolabial flaps are commonly used. With these techniques nasolabial and perialar skin is subdermally dissected and turned over into the defect to create both the inner and outer lining of the ala. If there is also loss of the perialar and nasolabial skin, such techniques become impossible. With a modification it is still possible to reconstruct both the ala of the nose and the perialar/nasolabial skin in one operation. A V/Y sliding flap from the cheek with a side extension from the lower nasolabial fold used as a turn-over flap is dissected. With this technique it is also possible to reconstruct isolated loss of the ala of the nose.

Aged↗
PubMed2000

[Flexor and extensor tendon injuries of the hand].

Injuries of the flexor tendon are usually open injuries. In most cases primary treatment is therefore seldom performed by orthopaedic surgeons. This is different for injuries of the extensor tendon. Three quarters of injuries of the extensor tendon are closed injuries. Therefore we do go into primary and secondary reconstruction of the flexor tendon, but focus on primary and secondary reconstruction of the extensor tendon in the most common zones (1, Th I, 3, Th III).

Finger Injuries↗
PubMed2000

Real-time interactive virtual endoscopy of the tracheo-bronchial system: influence of CT imaging protocols and observer ability.

OBJECTIVE: To evaluate the influence of different spiral CT examination protocols suitable for clinical use on image quality and to assess the observer dependence in interactive real-time virtual bronchoscopy. METHODS AND PATIENTS: Real-time perspective volume rendering of the airways in twenty normal patients based on four different spiral CT examination protocols was evaluated by four observers in regard to the order of depictable bronchi. RESULTS: Best results were obtained using an examination protocol with a small beam collimation and a maximum pitch. Depending on the observer's ability to control the fly path and the orientation of the bronchi with respect to the slice plane up to sixth order bronchi could be depicted. Inter-observer variability was up to two branching orders. CONCLUSION: The performance of virtual bronchoscopy strongly depends on the applied CT examination protocol and the observers experience with perspective volume rendering. Both of which have to be taken into account when virtual bronchoscopy is compared with fiberoptic bronchoscopy.

Adult↗
PubMed2000

Treatment of opioid-dependent pregnant women with buprenorphine.

AIMS: To assess the maternal and fetal acceptability of buprenorphine and neonatal abstinence syndrome (NAS) in children born to buprenorphine-maintained mothers. DESIGN AND SETTING: Open-label, flexible dosing, inpatient induction with outpatient maintenance, conducted at the University of Vienna within the existing pregnancy and drug addiction program. PARTICIPANTS: Fifteen opioid-dependent pregnant women. INTERVENTION: Sublingual buprenorphine tablets (1-10 mg/day). MEASUREMENTS: Mothers: withdrawal symptoms (Wang Scale), nicotine dependence (Fagerström Scale: FTQ) and urinalysis. Neonates: birth outcome and NAS (Finnegan Scale). FINDINGS: All subjects were opioid-, nicotine- and cannabis-dependent. Buprenorphine was well tolerated during induction (Wang Score < or = 4) and illicit opioid use was negligible (91% opioid-negative). All maternal, fetal and neonatal safety laboratory measures were within normal limits or not of clinical significance. Mean birth outcome measures including gestational age at delivery (39.6 +/- 1.5 weeks), Apgar scores (1 min = 8.9; 5 min = 9.9; and 10 min = 10), birth weight (3049 +/- 346 g), length (49.8 +/- 1.9 cm) and head circumference (34.1 +/- 1.8 cm) were within normal limits. The NAS was absent, mild (without treatment) and moderate (with treatment) in eight, four and three neonates, respectively. The mean duration of NAS was 1.1 days. CONCLUSIONS: Buprenorphine appears to be well accepted by mother and fetus, and associated with a low incidence of NAS. Further investigation of buprenorphine as a maintenance agent for opioid-dependent pregnant women is needed.

Buprenorphine↗
PubMed2000

Monitoring of the internalization of neuropeptide Y on neuroblastoma cell line SK-N-MC.

Neuropeptide Y (NPY) is an important neuromodulator in the central and peripheral nervous system. The peptide acts through different NPY receptor subtypes (Y1-Y5, y6) that belong to the family of G protein-coupled receptors. In general, cellular responses to prolonged exposure to agonists of G protein-coupled receptors are attenuated, often through internalization of the receptors and their bound ligands. In this study, a fluorescent labeled NPY derivative was synthesized and characterized to investigate the internalization of NPY in the human neuroblastoma cell line SK-N-MC. Internalization was proven by binding experiments and subsequent acidic washing as well as by direct visualization by means of confocal laser scanning microscopy. Approximately 20-30% of the fluorescent labeled NPY and a tritium-marked NPY were resistant to acid removal of cell surface-bound ligands indicating internalization. Extracellular fluorescent labeled NPY was found to be distributed heterogeneously in a clustered pattern, which suggests that the ligand-receptor complex is collected in pits and caveolae followed by endocytosis.

Amino Acid Sequence↗
PubMed2000

A combined V-Y advancement-turnover flap for simultaneous perialar and alar reconstruction.

A modification to a standard nasolabial flap is described for the simultaneous reconstruction of confluent perialar and full thickness alar defects. The main body of the flap is advanced to cover the external surface of the perialar and alar defects. A side extension to the flap, based only on a dermal blood supply, is turned over, to line the reconstructed alar rim.

Aged↗
PubMed2000

The use of an in situ curing hydroxyapatite cement as an alternative to bone graft following removal of enchondroma of the hand.

Following curettage of enchondromata of the phalanges we filled the resultant bone cavity with hydroxyapatite cement in eight patients to avoid cancellous bone grafting. This material differs significantly from the ceramic hydroxyapatite commonly used in clinical practice. It is produced by the combination of two calcium phosphates which, in the presence of water, form a paste that cures to a solid implant with a microporous structure. Like ceramic hydroxyapatite, this cement is highly biocompatible and does not provoke a foreign body giant cell reaction, a sustained inflammatory response or a toxic reaction. We performed a prospective study with X-rays and clinical assessment up to 1 year after the operation. There were no complications, and all patients regained full function of the hand.

Adult↗
PubMed2000

Bile and acid reflux in long and short segment Barrett's esophagus, and in reflux disease.

Gastroesophageal acid reflux (GER) is the primary risk factor for gastroesophageal reflux disease (GERD). In long segment Barrett's esophagus (LSBE) duodenogastroesophageal reflux (DGER) parallels acid reflux. The role of GER and DGER in short segment Barrett's esophagus (SSBE) remains to be determined. The aim of the present prospective study was to investigate the esophageal bile and acid reflux in patients with LSBE, SSBE and patients with GERD. Three groups of patients were studied: Patients with LSBE (n = 12), SSBE (n = 20) and patients with GERD without intestinal metaplasia (n = 33). Subjects underwent esophageal manometry and simultaneous 24-h pH and bile monitoring (Bilitec 2000). The thresholds for GER and DGER were a deMeester score > 14.7 and an absorbance value > 0.2 for 10.9% of total period, respectively. GER did not differ between the groups (p > 0.05). However, DGER differed between patients with LSBE, SSBE and GERD (14.7 vs 2.1 vs 2.1, respectively; p < 0.05). H. pylori status did not influence GER and DGER significantly. In contrast to patients with LSBE the DGER does not seem to play an important role in patients with SSBE and patients with GERD. This result indicates a different etiopathology of both long and short segment Barrett's esophagus.

Adult↗
PubMed2000

Application of coloring theory to reduce intensity modulated radiotherapy dose calculations.

Coloring theory is applied to reduce the dose calculations under intensity modulated radiotherapy. Intensity modulated radiotherapy varies the intensity profile across the beam. The beam face is divided into a panel of small squares or "bixels." Each square may be opened or closed for different lengths of time by moving collimator leaves in and out of the beam. It has been shown that the distribution of dose from radiation directed through any open square depends on whether the adjacent squares are opened or closed. Taking the states of neighboring bixels into account greatly increases the required dose calculations. There are 2(8) possible ways to select open or closed states for the eight neighbors of a given bixel. Each combination represents one coloring of a 3 x 3 panel, and each coloring demands a separate dose calculation. The number of calculations is reduced by considering the symmetries of a square. The 256 possible colorings can be divided into 51 distinct patterns through application of Burnside's theorem. Each pattern consists of selections of closed bixels that are the same except for a symmetric transformation of coordinates. If the symmetry between x and y coordinates is broken by collimator leaves whose ends and sides have different effects on bordering bixels, the number of patterns increases to 84. The theoretic gain in the number of calculations through the application of Burnside's theorem is fivefold if bixel borders are symmetric, and threefold if the borders are asymmetric. The results are applied to examples of generated intensity maps. The symmetry rules divide the bixel arrangements into proportionately fewer patterns as the intensity maps become larger, allowing computational gains to be achieved.

Color↗