Simulation of transmission electron microscope images of biological specimens.

We present a new approach to simulate electron cryo-microscope images of biological specimens. The framework for simulation consists of two parts; the first is a phantom generator that generates a model of a specimen suitable for simulation, the second is a transmission electron microscope simulator. The phantom generator calculates the scattering potential of an atomic structure in aqueous buffer and allows the user to define the distribution of molecules in the simulated image. The simulator includes a well defined electron-specimen interaction model based on the scalar Schrödinger equation, the contrast transfer function for optics, and a noise model that includes shot noise as well as detector noise including detector blurring. To enable optimal performance, the simulation framework also includes a calibration protocol for setting simulation parameters. To test the accuracy of the new framework for simulation, we compare simulated images to experimental images recorded of the Tobacco Mosaic Virus (TMV) in vitreous ice. The simulated and experimental images show good agreement with respect to contrast variations depending on dose and defocus. Furthermore, random fluctuations present in experimental and simulated images exhibit similar statistical properties. The simulator has been designed to provide a platform for development of new instrumentation and image processing procedures in single particle electron microscopy, two-dimensional crystallography and electron tomography with well documented protocols and an open source code into which new improvements and extensions are easily incorporated.

Molecular cryo-electron tomography of vitreous tissue sections: current challenges.

Electron tomography of vitreous tissue sections (tissue TOVIS) allows the study of the three-dimensional structure of molecular complexes in a near-native cellular context. Its usage is, however, limited by an unfortunate combination of noisy and incomplete data, by a technically demanding sample preparation procedure, and by a disposition for specimen degradation during data collection. Here we outline some major challenges as experienced from the application of TOVIS to human skin. We further consider a number of practical measures as well as theoretical approaches for its future development.

Stem cells and reproductive medicine.

For decades it has remained as a central dogma in dogma in reproductive biology that female mammals are born with a set non-renewable number of germ cells in the ovary. Recent revolutionary studies challenged this dogma by showing postnatal oogenesis in the adult ovary. In this review article the formation of primordial germ cells (PGC), the precursors of adult gametocytes beginning from their specification to their migration to prospective gonads will be reviewed with a special emphasis on stem cells studies that obtained gametocytes from germ and non germline stem cells.

Correlation between maternal thyroid function tests and endothelin in preeclampsia-eclampsia.

OBJECTIVE: To investigate the relationship between results of maternal thyroid function tests and endothelin levels in preeclamptic or eclamptic women. METHODS: Thyroid hormones, TSH, and endothelin were measured in plasma or serum from 37 proteinuric, preeclamptic or eclamptic women and 20 normotensive, nonlaboring, pregnant women. Subjects were subdivided into four groups according to hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome and birth weights of infants with respect to gestational age. RESULTS: A significant decrease in concentrations of total thyroxine (T4) (13.76+/-1.84 microg/dL versus 10.00+/-1.48 microg/dL, P < .05), total triiodothyronine (T3) (180.58+/-30.84 ng/dL versus 141.16+/-27.31 ng/dL, P < .01), free T4 (1.45+/-0.27 ng/dL versus 1.10+/-0.21 ng/dL, P < .01) and free T3 (3.32+/-0.56 pg/mL versus 2.41+/-0.60 pg/mL, P < .01) and a significant increase in TSH (1.55+/-0.89 microIU/mL versus 2.96 +/-1.07 microIU/mL, P < .05) and endothelin (2.31+/-0.61 pg/mL versus 6.11+/-1.41 pg/mL, P < .001) levels were observed in the preeclamptic-eclamptic group compared with the normotensive group. Also, women without HELLP syndrome and without small-for-gestational-age infants had elevated levels of thyroid hormones and decreased levels of TSH and endothelin compared with other subgroups, but stastical significance was reached only in total T4 (P < .05), TSH (P < .05), and endothelin (P < .001). Birth weights of infants born to preeclamptic or eclamptic women correlated positively with total T4 (P < .01) and total T3 (P < .01) and negatively with TSH (P < .01) levels. A more significant negative correlation was found in preeclamptic-eclamptics (P < .001) between birth weight and endothelin levels than in control subjects (P < .05). Endothelin levels in preeclamptic or eclamptic women correlated negatively with total T4 (P < .01), total T3 (P < .05), free T4 (P < .05), and free T3 (P < .05) and positively with TSH levels (P < .01) compared with control subjects. CONCLUSION: Moderate decreases in thyroid hormones with concomitant increases in TSH levels in maternal serum correlated with severity of preeclampsia or eclampsia and high levels of endothelin. Changes in results of thyroid function tests induced by preeclampsia or eclampsia might be consequences of the dysfunction in the hypothalamic-pituitary-thyroid axis, secondary to the disease itself.

Hyaluronic acid plus heparin for improved efficacy in prevention of adhesion formation in rat uterine horn model.

OBJECTIVE: To determine the effectiveness of hyaluronic acid (HA) and heparin [unfractioned heparin (UH) or low molecular weight heparin (LMWH)] combination in reducing adhesion formation in a rat uterine horn model. STUDY DESIGN: Prospective, randomized, comparative study in a rat model was done in Surgical Research Laboratory, Erciyes University. A standard lesion was created by unipolar electrocautery in 120 uterine horns of total 60 female Wistar-Albino rats. Animals were then randomly assigned into four groups, each consisting of 15 animals: (1) control, no adjuvant given; (2) HA, 1 ml of 0.4% solution given onto each horn preoperatively; (3) HA, 1 ml of 0.4% solution given preoperatively plus 1 ml of UH given postoperatively; (4) HA, 1 ml of 0.4% solution given before injury plus 1 ml of LMWH given after injury. A second-look laparotomy was performed two weeks after surgery. The number of horns with adhesion was determined and a scoring system applied. RESULT(S): The number of horns without adhesion formation was significantly higher in HA plus UH (P<0.05) and HA plus LMWH (P<0.01) groups compared to control group. The extent, severity and total scores of adhesion formation were also found to be significantly reduced in other groups when compared to control group. Combination of HA plus UH and HA plus LMWH significantly reduced all adhesion scores compared to HA alone. But a direct comparison of the ability of HA plus UH versus HA plus LMWH in reducing adhesion scores in the rat uterine horn yielded an insignificant difference. CONCLUSION: Administration of HA before injury followed by UH or LMWH given after injury has been documented to improve the efficacy of HA alone in reducing adhesion formation.