High-resolution, high-transmission soft x-ray spectrometer for the study of biological samples

We present a variable line-space grating spectrometer for soft x-rays that covers the photon energy range between 130 and 650 eV. The optical design is based on the Hettrick-Underwood principle and tailored to synchrotron-based studies of radiation-sensitive biological samples. The spectrometer is able to record the entire spectral range in one shot, i.e., without any mechanical motion, at a resolving power of 1200 or better. Despite its slitless design, such a resolving power can be achieved for a source spot as large as (30 x 3000) microm2, which is important for keeping beam damage effects in radiation-sensitive samples low. The high spectrometer efficiency allows recording of comprehensive two-dimensional resonant inelastic soft x-ray scattering (RIXS) maps with good statistics within several minutes. This is exemplarily demonstrated for a RIXS map of highly oriented pyrolytic graphite, which was taken within 10 min.

Time-resolved X-ray microscopy of nanoparticle aggregates under oscillatory shear

Of all the current detection techniques with nanometre resolution, only X-ray microscopy allows imaging of nanoparticles in suspension. Can it also be used to investigate structural dynamics? When studying the response to mechanical stimuli, the challenge lies in its application with a precision comparable with the spatial resolution. In the first shear experiments performed in an X-ray microscope, this has been accomplished by inserting a piezo actuator driven shear cell into the focal plane of a scanning transmission X-ray microscope. Thus shear-induced re-organization of magnetite nanoparticle aggregates could be demonstrated in suspension. As X-ray microscopy proves suitable for studying structural change, new prospects open up in physics at small length scales.

Isotope and temperature effects in liquid water probed by x-ray absorption and resonant x-ray emission spectroscopy

High-resolution x-ray absorption and emission spectra of liquid water exhibit a strong isotope effect. Further, the emission spectra show a splitting of the 1b1 emission line, a weak temperature effect, and a pronounced excitation-energy dependence. They can be described as a superposition of two independent contributions. By comparing with gas phase, ice, and NaOH/NaOD, we propose that the two components are governed by the initial state hydrogen bonding configuration and ultrafast dissociation on the time scale of the O 1s core hole decay.

Isotope and temperature effects in liquid water probed by x-ray absorption and resonant x-ray emission spectroscopy

High-resolution x-ray absorption and emission spectra of liquid water exhibit a strong isotope effect. Further, the emission spectra show a splitting of the 1b1 emission line, a weak temperature effect, and a pronounced excitation-energy dependence. They can be described as a superposition of two independent contributions. By comparing with gas phase, ice, and NaOH/NaOD, we propose that the two components are governed by the initial state hydrogen bonding configuration and ultrafast dissociation on the time scale of the O 1s core hole decay.

Fast track--different implications in pancreatic surgery

Concepts in "fast-track" surgery, which provide optimal perioperative care, have been proven to significantly reduce complication rates and decrease hospital stay. This study explores whether fast-track concepts can also be safely applied and improve the outcomes of major pancreatic resections. Perioperative data from 255 consecutive patients, who underwent pancreatic resection by means of fast-track surgery in a high-volume medical center, were analyzed using univariate and multivariate models. Of the 255 patients, 180 received a pancreatic head resection and 51 received distal, 15 received total, and 9 received segmental pancreatectomies. The patients were discharged on median day 10 with a 30-day readmission rate of 3.5%. The in-hospital mortality was 2%, whereas medical and surgical morbidities were 17 and 25%, respectively. Fast-track parameters, such as first stools, normal food, complete mobilization, and return to normal ward, correlated significantly with early discharge (p < 0.05). Patients' age, operation time, and early extubation proved to be independent factors of early discharge, shown through multivariate analysis (odds ratio: 4.0, 2.0, and 2.8, respectively; p < 0.05). Low readmission, mortality, and morbidity rates demonstrate that fast-track surgery is in fact feasible and safe and promotes earlier discharge without compromising patient outcomes.

Mode of action of methotrexate-albumin in a human T-cell leukemia line and activity against an MTX-resistant clone

Limitations of low mol. wt anticancer drugs are short tumor exposure times and toxicity to normal tissue. Methotrexate (MTX) covalently linked to human serum albumin (HSA) as a macromolecular carrier caused tumor regressions concomitant with a favorable toxicity profile in a clinical phase I trial (Hartung et aL, Clin. Cancer Res., 1999, 5, 753). We examined the uptake, intracellular degradation, metabolism and thymidylate synthase (TS) inhibition of MTX-HSA in the T-cell leukemia line CCRF-CEM and the MTX transport resistant clone CCRF-CEM/MTX. The number of MTX molecules per albumin molecule was determined by electrospray mass spectrometry. A loading ratio (LR) of approximately 1.4 mol MTX/albumin revealed intact complexes with one and two MTX molecules/albumin. In the complex with an LR of 5.7, albumin with up to 16 MTX molecules was seen. MTX-HSA was taken up by CCRF-CEM cells via endocytosis and cleaved by lysosomal enzymes. Liberated MTX was a poor substrate of folylpolyglutamate synthetase and was exported into the medium. TS was inhibited and cell survival was impaired by MTX-HSA in a time- and concentration-dependent manner. CCRF-CEM/MTX cells exhibited a growth inhibition of 30-40% after MTX-HSA treatment, but no TS inhibition. The alternative uptake route via endocytosis enables MTX-HSA to overcome transport resistance to MTX.

Comparative analysis of methotrexate polyglutamates in lymphoblast preparations from bone marrow and blood, and the contribution of residual red blood cells

PURPOSE

Blasts isolated from bone marrow aspirates or blood samples of patients with acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML) were compared for uptake of methotrexate (MTX) and formation of MTX polyglutamates (MTX-Glu(n)). Red blood cells (RBC) from the same patient samples were also analyzed.

METHODS

Blasts were isolated by standard density centrifugation. RBC were prepared from the pellet of the same centrifugation. MTX-Glu(n) were analyzed by means of HPLC and radiochemical quantification.

RESULTS

In lymphoblasts isolated from blood, the distribution patterns of MTX-Glu(n) were the same as in bone marrow lymphoblasts, but the total amount of MTX-Glu(n) accumulated in blood lymphoblasts was reduced by 41% 51% when compared to the same number of bone marrow lymphoblasts of the same patient. RBC accumulated MTX but no formation of MTX-Glu(n) occurred.

CONCLUSIONS

The determination of MTX and MTX-Glu(n) in lymphoblasts isolated from blood samples of patients with common ALL provides qualitative information on the capacity of the blasts to form MTX-Glu(n) since distribution patterns of MTX and MTX-Glu(n) parallel that of bone marrow lymphoblasts. The amounts of MTX-Glu(n) accumulated, however, were much lower in blood lymphoblasts. Blood lymphoblasts are therefore not useful for a quantitative analysis of MTX-Glu(n). The contribution of RBC to MTX and MTX-Glu(n) in vitro is only marginal and residual RBC in lymphoblast preparations from bone marrow can therefore be ignored.

Evaluation of the ADVIA Centaur TSH-3 assay

An analytical evaluation of the thyroid stimulating hormone (TSH-3) assay on the Bayer ADVIA Centaur immunoassay system was performed. General analytical requirements (linearity, resistance to typical interferences, absence of a carry-over effect) were fulfilled and reproducibility was satisfactory. Inter-assay coefficient of variation (CV) of a human serum pool with a concentration of 0.014 mU/l was 22.3%; at concentrations between 0.26 and 83 mU/l CV was below 6%. Method comparison study demonstrated close agreement of TSH results compared to those obtained with the Roche Elecsys 2010 TSH assay (ADVIA Centaur = 1.08 x Elecsys - 0.18 mU/l; r=0.987; n=324). Handling and practicability of the ADVIA Centaur system proved to be convenient with a very high sample throughput. We conclude that the ADVIA Centaur TSH-3 assay meets requirements for clinical use.

Emergency carotid endarterectomy

OBJECTIVE

Evaluation of the therapeutical efficacy of emergency carotid endarterectomy (CEA) in neurologically unstable patients.

PATIENTS AND METHODS

Three groups of a consecutive series of 71 emergency CEAs performed from 1980 to July 1998 were classified: (1) acute onset of severe stroke (n = 16), (2) progressive stroke/stroke in evolution (n = 34), and (3) crescendo transient ischemic attacks (n = 21). Cerebral coma, cerebral haemorrhage, and major ischemic stroke established in cranial computed tomography scans were contraindications for surgery. The neurological outcome was assessed by the modified Rankin scale. Long-term survival and long-term stroke recurrences were analyzed.

RESULTS

The recovery/minor stroke rates (Rankin 0-3) in acute stroke, progressive stroke, and crescendo transient ischemic attacks were 56.3, 76.4 and 80.9%, respectively; the combined major stroke/mortality rates (Rankin 4-6) were 43.7, 23.6 and 19.1%, respectively. Intraoperative angiography in 39 patients detected early carotid reocclusions in 2 and intracranial embolism in 7 patients. Local application of thrombolytic agents (n = 5) may contribute to a better neurological outcome in emergency CEA. Life table probabilities of major strokefree survival were 74.5, 71.6, and 53.7% after 1, 2, and 5 years, respectively (including perioperative strokes). Life table probabilities to suffer no stroke recurrence during follow-up were 96.7, 96.7 and 85.3%, respectively (perioperative strokes excluded).

CONCLUSIONS

Emergency CEA may be worthwhile in selected patients. Completion angiography is mandatory. Emergency CEA should be included in therapeutic strategies for ischemic stroke.

Mechanisms of resistance to methotrexate in childhood acute lymphoblastic leukemia: circumvention of thymidylate synthase inhibition

PURPOSE

In about 25% of patients suffering from acute lymphoblastic leukemia (ALL) treatment failures occur that are most likely due to development of resistance to methotrexate (MTX). Blasts from patients with ALL were evaluated for MTX uptake, formation of long-chain MTX polyglutamates (MTX-Glu5+6), cytotoxicity and thymidylate synthase inhibition by MTX and compared to blasts from patients with acute myelogenous leukemia (AML).

METHODS

Radioactively labeled MTX-Glu(n) were analyzed by means of HPLC. Thymidylate synthase activity was measured by a tritium-release assay. Cytotoxicity was determined by trypan blue exclusion.

RESULTS

In most ALL blasts (n = 9) large amounts of MTX-Glu5+6 (1.06-7.03 pmol/10(7) cells) and high cytotoxicity (43.5% 92.7%) were found, while in others small amounts of MTX-Glu5+6 (0.0-0.39 pmol/10(7) cells) caused only weak cytotoxicity (6.0% 27.9%) (n = 5, 2 relapsed patients). Resistance to MTX in blasts from AML patients (n = 5) was also caused by reduced synthesis of MTX-Glu5s+6 (0.0-0.42 pmol/10(7) cells). In contrast, some ALL blasts (n = 7, 4 relapsed patients) were able to survive MTX treatment despite large amounts of MTX-Glu5+6 (1.5-5.05 pmol/10(7) cells) and extensive thymidylate synthase inhibition.

CONCLUSIONS

Since the majority of ALL patients were examined at first diagnosis, an inherent mechanism of resistance seems most likely. We propose a mechanism based on the switch of thymidylate synthesis to the salvage pathway.

[Computer-based training exemplified by the carotid artery]

The purpose of computer-based training (CBT) is interactive use of multimedia components, such as text, graphics, animation, sound, digital slide shows, and videos. This CD-ROM illuminates different aspects of carotid surgery: cerebrovascular insufficiency, sonographic and neuroradiological diagnostics, indications and results of carotid surgery in the literature, perioperative complications and new developments such as interventional procedures. Digital imaging (60 minutes of video sequences and 250 graphics) especially focus on operative standard procedures (conventional and eversion technique) and alternative methods. CBT is an evolving supplement to improve education programs in vascular surgery.

The effect of stepwise cerebral hypoperfusion on energy metabolism and amyloid precursor protein (APP) in cerebral cortex and hippocampus in the adult rat

To study the relationship between cerebral blood flow, energy metabolism, and the formation of amyloid precursor protein (APP), an in vivo animal model was established in which stepwise long-term cerebral hypoperfusion states were induced. Adult rats underwent a stepwise chronic cerebral hypoperfusion by crosswise occlusion of the carotid and vertebral arteries with different periods and severity of hypoperfusion until the final steady-state experiment. Investigations of metabolic compounds were done in hippocampus and parietotemporal cerebral cortex. The analysis of energy-rich phosphates and adenosine was examined by HPLC analysis. Substrate concentrations of pyruvate and lactate were measured spectrophotometrically. The APP holoprotein was investigated by immunblot technique. Long-term cerebral hypoperfusion induced a decrease of energy-rich phosphates in the brain areas studied, whereas the concentration of adenosine and the ATP turnover were increased. Pyruvate decreased, and lactate was increased, pointing to a shift in the cytoplasmatic redox state. More severe changes were found in parietotemporal cerebral cortex in comparison to the hippocampus. After 2-vessel occlusion, the concentration of APP decreased, whereas the APP concentration was significantly increased in rat brain after 4-vessel occlusion. It has been demonstrated for the first time in vivo that the reduction in cerebral energy metabolism alters the formation of APP due to cerebral hypoperfusion.

Time course of methotrexate polyglutamate formation and degradation in the pre-B-leukaemia cell line Nalm6 and in lymphoblasts from children with leukaemia

With the aim of investigation, the mechanisms of resistance to methotrexate (MTX) in children refractory to leukaemia-treatment, we established a method of analysing MTX metabolism in Nalm6 cells (human pre-B). The optimal extracellular concentration for MTX uptake and MTX polyglutamate (MTXPG2-6) formation at a density of 5 x 10(6) cells/ml was 1 microM 3H-MTX. After 15 h incubation at this concentration, a plateau of 5 pmol/10(6) cells of total MTX accumulated in the form of equal amounts of polyglutamates 3, 4 and 5 and low amounts of MTX and polyglutamates 2 and 6. MTX preloaded cells rapidly lost MTX and MTXPG2 in MTX-free medium, while MTXPG5 was still formed and then degraded very slowly. After 8 h in medium without MTX, 40% of total MTXPG was lost, after 24 h, 70%. The method is feasible for patient blasts. The number of blasts isolated from bone marrow after diagnosis is enough to perform small kinetic studies. The uptake of MTX into patient blasts is about 1/10 of that in Nalm6 cells.