Proteomic profiling of beta-cells using a classical approach - two-dimensional gel electrophoresis.

Proteomics has rapidly become a major field of research in biology and medicine. Its main aim is to obtain a global overview of the expression pattern of proteins and their relationship in any given condition of a biological system. This knowledge is of particular interest to elucidate the pathogenesis of complex disorders, such as diabetes. Separation of proteins by two-dimensional gel electrophoresis (2-DE) followed by mass spectrometry (MS) for their identification is perhaps the most widely used proteomic approach. In this review we have focused our attention on studies that have taken advantage of these methodologies to investigate the proteome of pancreatic islets, beta-cells and insulinoma cells in different conditions. As beta-cells of the pancreatic islets produce and secrete insulin, the main hormone for control of glucose homeostasis, these analyses may help to elucidate the mechanisms regulating insulin secretion and the development of various forms of diabetes, as well as to identify drug targets for therapeutic approaches.

Novel ultrahigh resolution data acquisition and image reconstruction for multi-detector row CT.

We present and evaluate a special ultrahigh resolution mode providing considerably enhanced spatial resolution both in the scan plane and in the z-axis direction for a routine medical multi-detector row computed tomography (CT) system. Data acquisition is performed by using a flying focal spot both in the scan plane and in the z-axis direction in combination with tantalum grids that are inserted in front of the multi-row detector to reduce the aperture of the detector elements both in-plane and in the z-axis direction. The dose utilization of the system for standard applications is not affected, since the grids are moved into place only when needed and are removed for standard scanning. By means of this technique, image slices with a nominal section width of 0.4 mm (measured full width at half maximum=0.45 mm) can be reconstructed in spiral mode on a CT system with a detector configuration of 32 x 0.6 mm. The measured 2% value of the in-plane modulation transfer function (MTF) is 20.4 lp/cm, the measured 2% value of the longitudinal (z axis) MTF is 21.5 lp/cm. In a resolution phantom with metal line pair test patterns, spatial resolution of 20 lp/cm can be demonstrated both in the scan plane and along the z axis. This corresponds to an object size of 0.25 mm that can be resolved. The new mode is intended for ultrahigh resolution bone imaging, in particular for wrists, joints, and inner ear studies, where a higher level of image noise due to the reduced aperture is an acceptable trade-off for the clinical benefit brought about by the improved spatial resolution.

Radiation dose reduction to breast and thyroid during MDCT: effectiveness of an in-plane bismuth shield.

PURPOSE: To evaluate dose reduction and image deterioration using in-plane bismuth breast-shielding and thyroid-shielding for MDCT. MATERIAL AND METHODS: Skin and organ doses of thyroid and breast were measured with thermoluminescent dosimeters in a female Alderson-Rando Phantom with and without a 4-ply in-plane bismuth shield. Routine neck (120 kVp, 150 mAs(eff); 16 x 1.5 mm) and chest (120 kVp, 100 mAs(eff); 16 x 1.5 mm) scan protocols were simulated on a 16-row MDCT scanner in three different settings: without shielding, with the shield directly on the surface, and with a 1-cm-thick cotton spacer between surface and shield. Image noise was quantified and compared using the t test. RESULTS: On average, shielding resulted in a 47% organ-dose reduction for the thyroid and 32% for the breast. Placement of the spacer between shield and surface had no significant impact on the measured doses, but significantly decreased the image noise (P < 0.05). CONCLUSION: In-plane bismuth breast and thyroid shielding significantly decreases radiation dose in MDCT without deteriorating image quality.

Estimation of radiation exposure in low-dose multislice computed tomography of the heart and comparison with a calculation program.

The purpose of this study was to evaluate the achievable organ dose savings in low-dose multislice computed tomography (MSCT) of the heart using different tube voltages (80 kVp, 100 kVp, 120 kVp) and compare it with calculated values. A female Alderson-Rando phantom was equipped with thermoluminescent dosimeters (TLDs) in five different positions to assess the mean doses within representative organs (thyroid gland, thymus, oesophagus, pancreas, liver). Radiation exposure was performed on a 16-row MSCT scanner with six different routine scan protocols: a 120-kV and a 100-kV CT angiography (CTA) protocol with the same collimation, two 120-kV Ca-scoring (CS) protocols with different collimations and two 80-kV CS protocols with the same collimation as the 120-kV CS protocols. Each scan protocol was repeated five times. The measured dose values for the organs were compared with the values calculated by a commercially available computer program. Directly irradiated organs, such as the esophagus, received doses of 34.7 mSv (CTA 16x0.75 120 kVp), 21.9 mSv (CTA 16x0.75 100 kVp) and 4.96 mSv (CS score 12x1.5 80 kVp), the thyroid as an organ receiving only scattered radiation collected organ doses of 2.98 mSv (CTA 16x0.75 120 kVp), 1.97 mSv (CTA 16x0.75 100 kVp) and 0.58 mSv (CS score 12x1.5 80 kVp). The measured relative organ dose reductions from standard to low-kV protocols ranged from 30.9% to 55.9% and were statistically significant (P<0.05). The comparison with the calculated organ doses showed that the calculation program can predict the relative dose reduction of cardiac low photon-energy protocols precisely.

[On the way to isotopic spatial resolution: technical principles and applications of 16-slice CT]. / Auf dem Weg zur isotropen räumlichen Auflösung: Technische Grundlagen und Anwendungen der 16-Schicht-CT.

The broad introduction of multi-slice CT by all major vendors in 1998 was a milestone with regard to extended volume coverage, improved axial resolution and better utilization of the tube output. New clinical applications such as CT-examinations of the heart and the coronary arteries became possible. Despite all promising advances, some limitations remain for 4-slice CT systems. They come close to isotropic resolution, but do not fully reach it in routine clinical applications. Cardiac CT-examinations require careful patient selection. The new generation of multi-slice CT-systems offer simultaneous acquisition of up to 16 sub-millimeter slices and improved temporal resolution for cardiac examinations by means of reduced gantry rotation time (0.4 s). In this overview article we present the basic technical principles and potential applications of 16-slice technology for the example of a 16-slice CT-system (SOMATOM Sensation 16, Siemens AG, Forchheim). We discuss detector design and dose efficiency as well as spiral scan- and reconstruction techniques. At comparable slice thickness, 16-slice CT-systems have a better dose efficiency than 4-slice CT-systems. The cone-beam geometry of the measurement rays requires new reconstruction approaches, an example is the adaptive multiple plane reconstruction, AMPR. First clinical experience indicates that sub-millimeter slice width in combination with reduced gantry rotation-time improves the clinical stability of cardiac examinations and expands the spectrum of patients accessible to cardiac CT. 16-slice CT-systems have the potential to cover even large scan ranges with sub-millimeter slices at considerably reduced examination times, thus approaching the goal of routine isotropic imaging.

[5 years of "concerted action dose reduction in CT" -- what has been achieved and what remains to be done?]. / 5 Jahre Konzertierte Aktion Dosisreduktion CT--was wurde erreicht, was ist noch zu tun?

In May 1998, the German "Concerted Action Dose Reduction in CT" was founded by all parties involved in CT. Its intention was to achieve a significant reduction of the radiation exposure caused by CT, a matter that has increasingly been considered a major challenge since the early nineties. As a result of a number of joint efforts, the essential preconditions have been established by now. The fifth anniversary of the Concerted Action gave rise for both retrospection and outlook on the tasks that have already been accomplished and those that still need to be done. For this purpose, a one-day symposium took place in Berlin on November 4, 2003. The contents of a total of 18 contributions will be outlined here in brief.

Stereolithographic models simulating trabecular bone and their characterization by thin-slice- and micro-CT.

The analysis of bone structure in vivo is an important goal in osteoporosis, because the determination of bone mineral density alone is insufficient to predict whether an individual patient will eventually suffer an osteoporotic fracture or not. An additional structural analysis may significantly improve the statistical assessment of fracture risk. In this study we present a method to generate realistic although enlarged 3D phantoms of trabecular bone. These phantoms are useful in characterizing the potential of in vivo imaging procedures for the analysis of bone structure and to verify textural or structural analysis methods applied to these images. Our phantoms are based on a real trabecular bone specimen that was converted to a plastic model using the technique of stereolithography. The trabecular network is modeled by hydroxyapatite. Limitations of the stereolithographic process prevent the generation of exact 1:1 replicas of the real bone. A histomorphometric analysis of microCT scans of the phantoms showed that an excellent replication of the bone structure could be achieved in phantoms enlarged by a factor of 2.5 with "trabecular" hydroxyapatite concentrations up to 400 mg/cm3. In order to demonstrate the usefulness of our phantoms, we investigated one of them with various thin-slice CT protocols using clinical single- and multi-slice spiral CT scanners. The enlargement of the phantoms limits their use on high spatial resolution CT scanners (resolution >20 lp/cm). The limited hydroxyapatite concentration requires enhanced exposure rates for the phantoms scans to offset the larger impact of noise due to the lower contrast in the phantoms.

[Xenon computerized tomography of kidney transplants]. / Xenon-Computertomographie von Nierentransplantaten.

Xenon-CT is an established method for determining cerebral perfusion, while applications in other organs are rare. We evaluated the diagnostic potential of measuring the regional Renal Blood Flow (rRBF) in 10 patients with transplanted kidneys by xenon-CT. We found significant differences in the rRBF between the renal medulla and the cortex. There were no differences between normal renal transplants and transplants with chronic rejection.

A comparison of conventional and spiral CT: an experimental study on the detection of spherical lesions.

OBJECTIVE: It is accepted that spiral CT scanning may offer significant advantages in a number of clinical applications. There is still some concern with respect to image quality, however, since slice sensitivity profiles are slightly broadened due to the table motion. We carried out theoretical analysis, phantom measurements, and computer simulations to evaluate and to compare contrast and spatial resolution for conventional and for spiral scanning. Special emphasis was put on the task of detecting spherical lesions. MATERIALS AND METHODS: For standard test objects that measure only resolution in the scan plane, no significant difference between conventional and spiral scanning was observed. We therefore designed a phantom setup that allowed us to place spheres of arbitrary diameter and contrast in arbitrary positions to test three-dimensional (3D) resolution. RESULTS: For conventional CT, both lesion contrast and the degree of spatial separation of lesions observed depend on the relation of the start position of the scan series to the random location of a sphere or lesion. Spiral CT offers space-invariant resolution due to its continuous scanning. Small lesion contrast may be improved by up to a factor of 1.8 when compared with conventional CT since slices can be centered retrospectively. Measurements and simulations were in excellent agreement. CONCLUSION: We conclude that spiral CT can offer improved 3D contrast and spatial resolution. To exploit these advantages, images should be reconstructed in spiral CT at increments of less than half the distance traveled during one 360 degrees tube rotation. With four to five images per such interval, usually equal to the slice width, results very close to the theoretical optimum are achieved. Many of the presented considerations and results apply to other slice imaging modalities like MRI in analogous fashion.

[Material selective imaging and density measurement with the dual energy method. III. Determination of bone mineral of the spine with CT]. / Materialselektive Bildgebung und Dichtemessung mit der Zwei-Spektren-Methode. III. Knochenmineralbestimmung mit CT an der Wirbelsäule.

Quantitative computed tomography for measuring vertebral bone mineral content offers high sensitivity and reproducibility. However, several systematic errors of the method have to be considered, such as the influence of fat present in the spongiosa in varying concentrations as well as beam hardening effects and different calibration methods. The unknown fat content of the spongiosa of the vertebral bodies can be responsible for errors up to 30%. Beam hardening effects result in comparatively minor errors which can moreover be easily corrected via reference phantoms. The calibration method, on the other hand, results in potentially major systematic deviations due to the necessarily arbitrary determination of the reference points. These deviations must be taken into account especially in cross-comparisons of measured data. Dual energy methods enable a highly selective determination of the density of calcified tissue and soft tissue and decisively reduces the systematic errors mentioned above. The order of magnitude of the individual errors for different CT techniques was assessed by means of phantom studies and clinical studies.

[Material-selective imaging and density measurement using the dual-energy method. I. Principles and methodology]. / Materialselektive Bildgebung und Dichtemessung mit der Zwei-Spektren-Methode. I. Grundlagen und Methodik.

The principles of the Dual Energy method are discussed from two perspectives: a clear illustration of the method and an exact presentation of the principles involved. The principles apply to both radiography and computed tomography. The method was implemented on a CT scanner (SOMATOM DR, Siemens AG). Dual Energy images enable highly selective imaging based on the determination of density values for calcified and soft tissue. Images may also be reconstructed that are based on other parameters such as electron density and effective atomic number. The degree to which selective imaging is possible is discussed. Examples of Dual Energy clinical applications for radiography and computed tomography are presented. More detailed information will be available in future contributions.

Studies of paranasal sinus ventilation by xenon-enhanced dynamic CT.

A new method to determine ventilation of the paranasal sinuses is presented. After insufflation of pure stable xenon into the sinus system via the nasal cavity the gas wash-out is detected by means of quantitative dynamic computerized tomography. The measured time density curves allow to derive gas exchange parameters for all paranasal sinuses. We report mean gas exchange times for the maxillary, sphenoidal and frontal sinuses as well as the posterior ethmoidal cells obtained from 17 patient studies. Some clinical examples are discussed in detail. Compared to existing procedures, xenon-enhanced dynamic CT is the only non-invasive quantitative method to determine ventilation of all paranasal sinuses.

Monoclonal antibodies reactive with glioma cell lines derived from experimental brain tumors.

The production of hybridomas between X63-Ag8.653 myeloma cells and spleen cells from female BALB/c mice immunized with 79FR-G-41 glioma cells is reported. One hundred and six hybridoma clones were obtained secreting monoclonal antibodies (McAbs) against different target cells. Specificity tests (RIA, micro-ELISA) showed that McAbs produced by three hybridoma clones (13GC1, 14BC1, 14FC3) bound 79FR-G-41 glioma cells but did not react with fibroblasts, kidney and brain cells of newborn F344 rats. From the specificity analysis of two McAbs (13GC1, 14BC1) it is evident that these did not only react with 79FR-G-41 cells but also with other glioma cell lines (78FR-G-219, 78FR-G-284, 78FR-G-299 and 78FR-G-344) established from chemically induced rat brain gliomas. These results suggest, in accordance with the findings in human neuroectodermal tumors, the expression of common reactivity antigens in different brain tumors of glial origin. However, the McAbs obtained against experimental rat glioma cells did not recognize glioma cells derived from spontaneous brain tumors of dog or man. Immunofluorescence and immunoperoxidase tests indicate that there is a remarkable heterogeneity among cells of experimental glioma lines with respect to the expression of glioma associated determinants recognized by McAbs. The fact that only a variable number instead of the totality of tumor cells in any asynchronous and uncloned tumor cell population expresses, at a certain time, recognizable antigenic determinants has to be taken into account, particularly if they are considered to be employing McAbs as carrier molecules for diagnostic and therapeutic purposes.

[Infection hazards and complications following the use of IUDs]. / Infektionsrisiko und Komplikationen nach IUD-Applikation.

Own experiences on IUD-complications especially irregular bleedings and infections underline that modern plastic intrauterine devices are second-rate contraceptives. Compared to hormonal contraceptive drugs intrauterine devices have a higher pregnancy risk and increased rates of infections. Therefore the IUD is in our opinion not suited primary contraceptive method used without indication. Because of the relatively often occurring ascendant genital infections the application of intrauterine devices should not be carried out in nulliparae.

PIP: Incidence of complications in 552 IUD patients (12,290 cycles) is reported. The IUDs used were the Dana cor and Dana superlux. Complications were seen in 211 women: expulsion (58 patients), pregnancy with IUD in place (22), irregular bleeding or endometritis (116), adnexa involvement (32). IUDs were removed from 86 patients. Endometrial material obtained by dilation and curettage after IUD removal showed changes consistent with the development of endometritis. The intensity of the endometrial reaction (as well as contraceptive effectiveness) depends on the relation of the IUD's shape and dimensions to those of the uterine cavity. In the authors' view, IUDs are not the contraceptive of choice unless hormonal contraception is contraindicated.