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Biomedical subjects

L Lehr

Publications and source records attributed to L Lehr.

At least 19 recordsLinked to original sources
PubMed2005

Femtosecond dynamics after ionization: 2-phenylethyl-N,N-dimethylamine as a model system for nonresonant downhill charge transfer in peptides.

The cation of 2-phenylethyl-N,N-dimethylamine (PENNA) offers two local sites for the charge: the amine group and 0.7 eV higher in energy the phenyl chromophore. In this paper, we investigate the dynamics of the charge transfer (CT) from the phenyl to the amine site. We present a femtosecond resonant two-color photoionization spectrum which shows that the femtosecond pump laser pulse is resonant in the phenyl chromophore. As shown previously with resonant wavelengths the aromatic phenyl chromophore can be then selectively ionized. Because the state "charge in the phenyl chromophore" is the first excited state in the PENNA cation, it can relax to the lower-energetic state "charge in the amine site". To follow this CT dynamics, femtosecond probe photoabsorption of green light (vis) is used. The vis light is absorbed by the charged phenyl chromophore, but not by the neutral phenyl and the neutral or cationic amine group. Thus, the absorption of vis photons of the probe laser pulse is switched off by the CT process. For detection of the resonant absorption of two or more vis photons in the cation the intensity of a fragmentation channel is monitored which opens only at high internal energy. The CT dynamics in PENNA cations has a time constant of 80 +/- 28 fs and is therefore not a purely electronic process. Because of its structural similarity to phenylalanine, PENNA is a model system for a downhill charge transfer in peptide cations.

Dimethylamines↗
PubMed1999

Electron solvation in finite systems: femtosecond dynamics of iodide. (Water)n anion clusters

Electron solvation dynamics in photoexcited anion clusters of I-(D2O)n=4-6 and I-(H2O)4-6 were probed by using femtosecond photoelectron spectroscopy (FPES). An ultrafast pump pulse excited the anion to the cluster analog of the charge-transfer-to-solvent state seen for I- in aqueous solution. Evolution of this state was monitored by time-resolved photoelectron spectroscopy using an ultrafast probe pulse. The excited n = 4 clusters showed simple population decay, but in the n = 5 and 6 clusters the solvent molecules rearranged to stabilize and localize the excess electron, showing characteristics associated with electron solvation dynamics in bulk water. Comparison of the FPES of I-(D2O)n with I-(H2O)n indicates more rapid solvation in the H2O clusters.

Journal Article↗
PubMed1999

Cortical visual processing is temporally dispersed by luminance in human subjects.

Increasing the intensity of a stimulus such as luminance results in faster processing of the signal and therefore decreases simple motor reaction time (RT). We studied the latencies of visual evoked potentials (VEPs, N80, P100, N130) and RTs in eight subjects to flashing spots of light while varying the luminance of the spots from 1 to 1000 cd/m2. The data show that processing time as a function of intensity is modified not only at the retina but also at later processing sites. This indicates a temporal dispersion of the visual signal over the whole processing stream from visual input all the way to motor output.

Adult↗
PubMed1999

Nitric oxide end products in patients hospitalized for diarrhoea.

OBJECTIVE: Increased nitric oxide (NO) has been demonstrated in inflammatory bowel diseases (IBD). Plasma and urinary nitrite and nitrate are usually considered to reflect global NO generation. Recently it has been suggested that plasma nitrate may be a discriminant indicator between infectious enterocolitis (IC) and IBD. To investigate this hypothesis we compared plasma and 24 h urinary nitrite and nitrate in 13 healthy controls, 44 patients with IBD [Crohn's disease (CD) n = 30; ulcerative colitis (UC) n = 14], 16 patients presenting with IC and seven chronic radiation enterocolitis (RE) patients. RESULTS: Despite a trend towards higher plasma nitrate in IC (54.6+/-11.4 micromol/l) than in the other groups (CD: 38.4+/-4.8, UC: 34.8+/-8.4, RE: 34.7+/-7.5, controls: 31.1+/-5.2), this difference was not statistically significant. Urinary nitrate was higher in IBD, IC and RE than in controls, with no difference between these groups. Nitrite concentrations were not different. Nitrate levels were positively correlated with blood and 24 h urinary neopterin (e.g. plasma nitrate and blood neopterin: r = 0.54, P<0.0001), and in some cases, to C-reactive protein. CONCLUSIONS: High nitrate (in our case only urinary nitrate) appears to be secondary to the magnitude of the inflammation rather than the aetiology of the diarrhoea. It should therefore more likely be considered as a marker of the severity of the inflammatory response rather than used as a discriminant indicator between IC and IBD patients.

Case-Control Studies↗
PubMed1998

[Soluble tumor necrosis factor receptors in patients with systemic lupus erythematosus].

OBJECTIVE: To study the variations of type II soluble receptors for tumor necrosis factor (sR-TNF) in patients with systemic lupus erythematosus and investigate their use in the clinical setting. PATIENTS AND METHODS: Twenty-six patients with systemic lupus were followed for a mean 3 years. sR-TNF and other immunological parameters (C reactive protein, anti-DNA antibodies, C3 and C4 complement fractions, soluble receptors for interleukin 2) were measured in sera at different points of the disease course. The systemic lupus activity measure (SLAM) was determined at each point, and confronted with the biology results. The study was cross sectional for the group and longitudinal for the patients. RESULTS: sR-TNF was the immunological parameter which correlated best with SLAM. It also correlated with sedimentation rate, C reactive protein, thrombopenia, anemia, creatinine level, anti-DNA antibodies and sR-IL2. The longitudinal study pointed out however that this finding is not consistent for each patient. CONCLUSION: A rise in sR-TNF related to systemic lupus activity but is of limited practical interest for individual patient follow-up.

C-Reactive Protein↗
PubMed1997

[Concept and realization of nationally applicable clinic guidelines in the intra- and internet--a quality assurance measure in the health care system?].

This project aimed at the realisation of a database for clinical guidelines in abdominal surgery and oncology, which can be used within a hospital network as well as from the internet. The "Klinikmanual Chirurgie" (currently in German only) can be accessed via http://nt1.chir.med.tu-muenchen.de/manual.h tm worldwide and free of charge. An English version is in preparation.

Computer Communication Networks↗
PubMed1995

[Ambulatory surgery--definition, socioeconomic and legal aspects].

One of the most important intentions of GSG 1992 is the favourization of traditional ambulatory surgery by legislative measures. However in general surgery a much higher potential for a significant reduction in cases of classical hospitalization and thus concomitant substantial financial savings lies in short-stay eg. one-day/one-night procedures. At present methods of laparoscopic cholecystectomy, thyroid surgery and herniorrhaphy-together about 50% of common hospital patients-are developed enough to be practiced safely under this strategy. In the future further suitable techniques could evolve from minor access surgical concepts.

Ambulatory Surgical Procedures↗
PubMed1992

[Ambulatory surgery at the surgical clinic and polyclinic of the Munich Technical University].

Day-care and especially short-stay surgery were found attractive logistics for surgery of the hand, inguinal hernia repair, laparoscopic cholecystectomy, invasive measures for tumor staging such as diagnostic laparoscopy and implantation of vascular ports for chemotherapy. This new way of surgical organization is a practical alternative to overcome increasing limitations of hospitalization capacities and to conserve everyday surgery which is necessary for the teaching of students and surgical beginners within otherwise highly specialized institutions.

Ambulatory Surgical Procedures↗
PubMed1991

[Technique of laparoscopic cholecystectomy].

A new technique for laparoscopic cholecystectomy is described which regards as far as possible the conventional approach to cholecystectomy. Positioning of the operating team is identical to normal cholecystectomy, and the surgeon is able to use both hands to operate since the camera is handled by the assistant. Dissection of the infundibulum is performed in the socalled "tease-and-tear" technique. The peritoneal layer is opened by coagulation. The cystic duct and artery are bluntly dissected by a commercially available dissector. Fat and connective tissue are gently torn off from both structures. After closure of cystic duct and artery by clips, the gallbladder is cut out by thermocoagulation. 178 operations were performed by 8 surgeons; mean duration of the operation was 60 min. A change to open cholecystectomy was necessary in 2.5%. Three complications occurred, requiring reoperation in one case of insufficiency of the cystic duct and another one with intestinal perforation. In the third case, bile leakage from an aberrant bile-duct occurred but dried up spontaneously after a few days. No death occurred nor were there any lesions of the common bile-duct. Conclusively, this new technique seems to be safe and simple to teach due to its approximity to the conventional technique and is recommended as a standard procedure.

Cholecystectomy↗
PubMed1990

[Mononuclear cell activation in Crohn's disease. Evaluation using serum assay of neopterin and interleukin-2 soluble receptors].

To determine the degree of mononuclear blood cell activation in Crohn's disease (CD), 65 patients were prospectively investigated (22 with mild, 26 with moderate and 17 with severe disease). Serum levels of soluble receptors for interleukin-2 (SR-IL-2) were measured by ELISA. In CD patients SR-IL-2 levels were significantly higher (m = 707 +/- 326 U/ml) than in three other groups: 70 controls (m = 258 +/- 87 U/ml, p less than 0.0001); 8 patients with acute infectious colitis (m = 405 +/- 216 U/ml, p less than 0.0001); 101 HIV seropositive subjects (m = 564 +/- 216 U/ml, p less than 0.002). There was a positive correlation between SR-IL-2 level and the Van Hees activity index (r = 0.595, p less than 0.0001). On the other hand, the numbers of activated T cells (CD 3+, HLA DR+), CD 4+, CD 8+ and NK cells did not differ according to the CD activity groups. Furthermore, CD patients treated with steroids (n = 39) did not differ from those without any medication. As a marker of monocyte activation, serum neopterin level was determined by RIA. All CD patients considered as a group, serum neopterin level was 2.89 +/- 1.44 ng/l (n less than 2.5 ng/l). Neopterin level increased with disease activity (1.97 +/- 0.92 vs 3.10 +/- 1.46 vs 3.74 +/- 1.36, p less than 0.01), and was positively correlated with SR-IL-2 (r = 0.609, p less than 0.0001). These results suggest a monocyte-macrophage activation in CD, which parallels disease activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

[Crohn disease and ulcerative colitis from the surgical viewpoint].

Crohn's Disease and Ulcerative Colitis, both chronic-recurrent inflammatory bowel diseases, are totally different with respect to surgical indication and therapy. While in Crohn's Disease it is intended to achieve a longer interval of resting disease at typical complications or failure of drug-therapy, in Ulcerative Colitis definitive cure is possible. Because of the significant lower mortality and complication-rate of elective surgery compared to emergency cases, surgical treatment should be considered very early as therapeutic strategy. The resection area in Crohn's Disease should be confined to a minimum, because even a wide resection is no guaranty for nonrecurrence. In Ulcerative Colitis proctocolectomy provides a reliable protection against colonic carcinoma.

Anal Canal↗