A Thrombotic Stroke Model Based On Transient Cerebral Hypoxia-ischemia

Stroke research has endured many setbacks in translating neuroprotective therapies into clinical practice. In contrast, the real-world therapy (tPA thrombolysis) rarely produces benefits in mechanical occlusion-based experimental models, which dominate preclinical stroke research. This split between the bench and bedside suggests the need to employ tPA-responsive models in preclinical stroke research. To this end, a simple and tPA-reactive thrombotic stroke model is invented and described here. This model consists of transient occlusion of the unilateral common carotid artery and delivery of 7.5% oxygen through a face mask in adult mice for 30 min, while maintaining the animal rectal temperature at 37.5 ± 0.5 °C. Although reversible ligation of the unilateral carotid artery or hypoxia each suppressed cerebral blood flow only transiently, the combination of both insults caused lasting reperfusion deficits, fibrin and platelet deposition, and large infarct in the middle cerebral artery-supplied territory. Importantly, tail-vein injection of recombinant tPA at 0.5, 1, or 4 hr post-tHI (10 mg/kg) provided time-dependent reduction of the mortality rate and infarct size. This new stroke model is simple and can be standardized across laboratories to compare experimental results. Further, it induces thrombosis without craniectomy or introducing pre-formed emboli. Given these unique merits, the tHI model is a useful addition to the repertoire of preclinical stroke research.     

Custom-designed Laser-based Heating Apparatus for Triggered Release of Cisplatin from Thermosensitive Liposomes with Magnetic Resonance Image Guidance

Liposomes have been employed as drug delivery systems to target solid tumors through exploitation of the enhanced permeability and retention (EPR) effect resulting in significant reductions in systemic toxicity. Nonetheless, insufficient release of encapsulated drug from liposomes has limited their clinical efficacy. Temperature-sensitive liposomes have been engineered to provide site-specific release of drug in order to overcome the problem of limited tumor drug bioavailability. Our lab has designed and developed a heat-activated thermosensitive liposome formulation of cisplatin (CDDP), known as HTLC, to provide triggered release of CDDP at solid tumors. Heat-activated delivery in vivo was achieved in murine models using a custom-built laser-based heating apparatus that provides a conformal heating pattern at the tumor site as confirmed by MR thermometry (MRT). A fiber optic temperature monitoring device was used to measure the temperature in real-time during the entire heating period with online adjustment of heat delivery by alternating the laser power. Drug delivery was optimized under magnetic resonance (MR) image guidance by co-encapsulation of an MR contrast agent (i.e., gadoteridol) along with CDDP into the thermosensitive liposomes as a means to validate the heating protocol and to assess tumor accumulation. The heating protocol consisted of a preheating period of 5 min prior to administration of HTLC and 20 min heating post-injection. This heating protocol resulted in effective release of the encapsulated agents with the highest MR signal change observed in the heated tumor in comparison to the unheated tumor and muscle. This study demonstrated the successful application of the laser-based heating apparatus for preclinical thermosensitive liposome development and the importance of MR-guided validation of the heating protocol for optimization of drug delivery.     

Localization and segregation of lineage-specific cleavage potential in embryos of Caenorhabditis elegans

Summary Early embryogenesis of the nematode Caenorhabditis elegans is characterized by the continuous visibility of a germline and the stepwise separation of all somatic cells from it. Germline and somatic cells exhibit different cleavage patterns. Typical for the germline is a series of stemcell-like, unequal cleavages generating blastomeres, which differ in size, cell cycle periods, and fate. Typical for members of somatic cell lineages during early development are their equal and synchronous cleavages generating cells of similar appearance. Using a laser microbeam various experiments have been carried out to investigate the conditions that lead to the two different types of cleavage. Development of partial embryos demonstrates that the potential for germline-like cleavage is localized in the posterior region of the fertilized egg prior to both the formation of pronuclei and the posterior aggregation of germline-specific granules. Experimental alteration of the cleavage plane can result in a switch from unequal to equal cleavage, with an apparent correlation between the orientation of the mitotic spindle and the type of cleavage. Nuclear transfer experiments indicate that nuclei and centrioles are not involved in the decision as to which type of cleavage will be executed. Cytoplasmic transfer from soma-like to germline-like cleaving cells and vice versa does not alter the cleavage type in the recipient cell. But if separation of germline from soma is delayed after the removal of a centrosome, germline-like cleavage may be completely suppressed, all cells thereafter dividing soma-like.Dedicated to Professor A. Egelhaaf on the occasion of his retirement     

Probing cell-surface dynamics and mechanics at different scales

Recent advances in our understanding of the cell surfaces strongly rely on new physical methods and concepts. During last decades, microscopy techniques combined with statistical analysis and modelling have significantly improved the toolkit of life scientists. They provide quantitative ways to analyse diverse biological functions such as cell signalling and cell adhesion at different scales. Here, I review quantitative approaches to cell-surface dynamics and mechanics. I focus on two specific topics: how membrane molecules dynamically organize in membranes and how cell-surface mechanics can contribute to tissue morphogenesis. Robert Feulgen Prize 2009 Winner lecture presented at the 51th Symposium of the Society for Histochemistry in Stubai, Austria, 7–10 October 2009.     

Cover plus: ways of measuring plant canopies and the terms used for them

Aim: To clarify the concepts and terms that have been used in recording plant canopies and the methods used for measuring them. Concepts: The concepts considered are cover, top cover, repeated cover, number of layers, proportion of repeated cover and leaf area index (LAI). Variants include canopy cover, basal area and leaf area density. Other terms have been used in the past, some are now ambiguous and some are counter‐intuitive. Measurement: Cover and its related concepts can be measured by point intercept, line intercept, angle sampling, charting and image analysis, canopy transmittance, complete enumeration, clipping and allometry. The common procedure of adding the cover of individual species to calculate a “total cover” is invalid: a nonsense number is produced. Other measures of abundance: Cover‐abundance, density, frequency, biomass and calorific values can also be used to measure abundance. They are related to cover. Especially, shoot frequency at a point is cover (the point intercept method). Subjective estimates: There are severe problems with cover‐abundance scales, such as that of Braun‐Blanquet. Estimation of abundance “by eye”, by “informed guess”, etc. has too often compromised results in vegetation science.     

Bayesian analysis of parent‐specific transmission ratio distortion in seven Spanish beef cattle breeds

Transmission ratio distortion (TRD) is the departure from the expected Mendelian ratio in offspring, a poorly investigated biological phenomenon in livestock species. Given the current availability of specific parametric methods for the analysis of segregation data, this study focused on the screening of TRD in 602 402 single nucleotide polymorphisms covering all autosomal chromosomes in seven Spanish beef cattle breeds. On average, 0.13% (n = 786) and 0.01% (n = 29) of genetic markers evidenced sire‐ or dam‐specific TRD respectively. There were no single nucleotide polymorphisms accounting for both sire‐ and dam‐specific TRD at the same time, and only one marker (rs43147474) accounted for (sire‐specific) TRD in all seven breeds. It must be noted that rs43147474 is located in the fourth intronic region of the GTP‐binding protein 10 gene, and this locus has been previously linked to the maintenance of mitochondria and nucleolar architectures. Alternatively, other candidate genes surround this hot‐spot for sire‐specific TRD in the cattle genome, and they are related to embryonic and postnatal lethality as well as prostate cancer, among others. This research characterized the distribution of TRD in the bovine genome, highlighting heterogeneous results when comparing across breeds.     

X-Ray Microanalysis and Phagocytotic Activity of Cultured Retinal Pigment Epithelial Cells in Hypoxia

Purpose: To investigate the influence of the functional and morphological changes induced in retinal pigment epithelial (RPE) cells by retinal ischemia, we evaluated the phagocytotic activity, the concentration of various elements, and ultrastructure in cultured RPE cells in hypoxia. Methods: The concentrations of oxygen in incubators were adjusted to 20, 10, and 1% by the addition of nitrogen for 72 hr. To observe phagocytotic activity and its relationship to actin filaments, the filaments of RPE cells incubated with fluoresbrite carboxylate YG microspheres were stained with rhodamine phalloidin. Some of the specimens were subjected to X-ray microanalysis by scanning electron microscope after being fixed, freeze-dried, and coated with carbon to investigate the cytoplasmic concentration of elements. A part of the latter specimens was also observed by transmission electron microscope after being embedded in epon and cut into ultrathin sections to see the ultra-structural changes inside cell. Results: Lowering oxygen concentrations from 20% to 1% swelled RPE cells and decreased the number of fluoresbrite carboxylate YG microspheres phagocytized by RPE cells. Phagocytosis of a large amount of latex beads (30 μl) for 24 hr in 1% oxygen caused a disruption of RPE cells. Na, S, and P were detected in RPE cells cultured in 20% oxygen. Reducing the oxygen concentration from 20 to 10 or 1% significantly decreased Na and increased S. Mitochondria were observed in RPE cells in 20 and 10% oxygen, but many vacuoles were observed in the cytoplasm in 1% oxygen. Conclusion: Hypoxia as low as 1% oxygen induced malfunction of phagocytosis and the fragility of RPE cells. We could speculate the imbalance of the electrolytes such as Na or a decrease of antioxidants such as glutathione containing S as a reason of disturbance of cell viability.     

准分子激光屈光性角膜切削术（PRK）治疗近视文献计量分析

通过对近十多年来的ＰＲＫ治疗近视的中外文文献计量分析，以揭示该技术的发展过程、现状及尚存在的问题，进一步科学地预测ＰＲＫ治疗近视的发展趋势。     

Prognostic Value of Serum Thyroglobulin Measured at 48 Hours Versus 72 Hours after Second Dose of Recombinant Human Thyrotropin in Surveillance of Well-Differentiated Thyroid Cancer

ObjectiveThe sensitivity of thyroglobulin (Tg) to detect differentiated thyroid cancer recurrence increases with the rise of the thyrotropin level. Since 1998, recombinant human thyrotropin (rhTSH) has been commercially available for this purpose. The traditional protocol for using rhTSH calls for 2 daily injections of rhTSH, followed by the measurement of Tg 72 hours after the second dose. In this study, we compared the performance of rhTSH-stimulated Tg (rhTSH-Tg) obtained at 48 versus 72 hours after the second rhTSH.MethodsA retrospective chart review of 1088 patients with thyroid cancer was conducted. Two hundred forty-nine rhTSH-Tg, without measurable Tg antibody, were identified, 134 of which were obtained at 48 hours (4-day test) and 115 at 72 hours after the second rhTSH (5-day test). The ability of rhTSH-Tg to identify recurrence or persistence of differentiated thyroid cancer and to predict response to therapy at the end of the study period was compared between the 2 groups.ResultsThe median duration of follow-up was 8 years. When recurrent/persistent cancer was present based on a combination of unstimulated Tg, imaging and procedures, the ratio of rhTSH-Tg ≥ 1 ng/mL was similar in both groups (P value: .153). The negative predictive value of rhTSH-Tg to predict response to therapy over the long term was 95% or higher in 4-day and 5-day tests.ConclusionTg measured 48 and 72 hours after the second dose of rhTSH may provide a comparable prognostic value. These results encourage further studies to identify new protocols to obtain rhTSH-Tg.     

The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry

Thermal noise in high-reflectivity mirrors is a major impediment for several types of high-precision interferometric experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. This is for example the case of future gravitational wave observatories, whose sensitivity to gravitational wave signals is expected to be limited in the most sensitive frequency band, by atomic vibration of their mirror masses. One promising approach being pursued to overcome this limitation is to employ higher-order Laguerre-Gauss (LG) optical beams in place of the conventionally used fundamental mode. Owing to their more homogeneous light intensity distribution these beams average more effectively over the thermally driven fluctuations of the mirror surface, which in turn reduces the uncertainty in the mirror position sensed by the laser light.We demonstrate a promising method to generate higher-order LG beams by shaping a fundamental Gaussian beam with the help of diffractive optical elements. We show that with conventional sensing and control techniques that are known for stabilizing fundamental laser beams, higher-order LG modes can be purified and stabilized just as well at a comparably high level. A set of diagnostic tools allows us to control and tailor the properties of generated LG beams. This enabled us to produce an LG beam with the highest purity reported to date. The demonstrated compatibility of higher-order LG modes with standard interferometry techniques and with the use of standard spherical optics makes them an ideal candidate for application in a future generation of high-precision interferometry.