Practical Confocal Microscopy and the Evaluation of System Performance

The laser scanning confocal microscope has enormous potential in many fields of biology. Currently there is a subjective nature in the assessment of a confocal microscope's performance by primarily evaluating the system with a specific test slide provided by the user's laboratory. To achieve better performance from the equipment, it is necessary to run a series of tests to ensure that the optical machine is functioning properly. We have devised these methods on the Leica TCS-SP and TCS-4D systems. Tests measuring field illumination, lens clarity, laser power output, dichroic functioning, spectral alignment, axial resolution, laser power stability, machine performance, and system noise were derived to test the Leica laser scanning confocal microscopy system. These tests should be applicable to other manufacturers' systems as well. The relationship between photomultiplier tube (PMT) voltage, laser power, and averaging using a 10-microm-diameter test bead has shown that the noise (coefficient of variation of bead intensity, CV) in an image increases as the PMT increases. Therefore increasing the PMT setting results in increased noise. For ideal image quality, it appears that it is better to decrease the PMT setting and increase laser power, as noise generated by high PMT settings will reduce the image quality far more than the bleaching caused by higher laser power. Averaging can be used to improve the image at high PMT values, provided the sample is not bleached by repeated passes of the laser.     

The Hirsute Woman: Challenges in Evaluation and Management

ObjectiveTo review the etiology, pathogenesis, diagnostic approach, and management of hirsutism.MethodsWe discuss the clinical course of hirsutism and provide our recommendations on the various treatment options available.ResultsHirsutism is a common clinical problem characterized by the presence of increased terminal hair growth in androgen-dependent areas of the skin. The development of hirsutism depends on the presence of the pilosebaceous unit, which is genetically determined, as well as the presence of the androgen receptor and intracellular 5α-reductase activity, which converts testosterone to its more active metabolite, dihydrotestosterone. A detailed history and physical examination and the following laboratory tests can diagnose most causes of hirsutism: early-morning follicular phase measurement of total testosterone, testosterone not bound to sex hormone-binding globulin, dehydroepiandrosterone sulfate, 17-hydroxypro- gesterone, prolactin, and thyrotropin levels. Oral contraceptive preparations may be effective monotherapy formild hirsutism. For the treatment of more severe hirsutism, oral contraceptive pills combined with spironolactone are as effective as oral contraceptive pills containing cyproter- one acetate, which are not available in the United States. Because of teratogenicity, spironolactone should be used with caution in premenopausal women when it is administered without an oral contraceptive pill. Metformin is an alternative therapy for hirsutism in women with polycystic ovary syndrome who have other indications for metformin use. Metformin is not as effective as antiandrogens for the management of hirsutism. The use of glucocorticoids, finasteride, or flutamide is not recommended.ConclusionsHirsutism can be evaluated with a detailed history and physical examination and a limited number of hormonal tests. Serious disorders presenting as hirsutism are rare and can be excluded with the recommended evaluation. Treatment is targeted at reducing the production and bioavailability of testosterone, as well as blocking target tissue androgen action. (Endocr Pract. 2011;17:807-818)     

Quantitative Evaluation of Marine Ecosystem Indicator Performance Using Food Web Models

Successful ecosystem-based management requires the selection and use of informative indicators of ecosystem status. We analyzed seven marine food web models to evaluate the performance of candidate indicators of ecosystem structure and function. The basic approach involved simulating fishing perturbations to each model, measuring the response of ecosystem attributes and candidate indicators to the perturbations, and testing the ability of the indicators to track changes in the values of the attributes. We focused on 22 ecosystem attributes, encompassing structural and functional properties that are relevant to a number of stakeholder groups but are typically difficult to measure directly (for example, food web structure, energy recycling). We tested for correlations between the attributes and 27 empirically tractable candidate indicators (for example, foraging guild biomasses, ratios of community-level groups) within each of the models and quantified consistency in indicator performance across the models. Our analysis suggests that no single indicator is sufficient to describe all of the ecosystem attributes, but at the same time highlights broad, catch-all indicators (for example, detritivores, jellyfish) and distinguishes the strongest attribute–indicator relationships. Ecosystem indicators consisting of lower-trophic level, higher-productivity functional groups tended to perform particularly well. We also identified indicators that showed strong or weak associations with different attributes, but together captured changes in nearly all of them. Examples of such complementary indicators include phytoplankton, zooplanktivorous fish, piscivorous fish, and trophic level of the catch. Quantitative approaches such as this one will enable managers to make informed decisions about ecosystem-scale monitoring in the oceans.     

基于量化的绩效考核模式可行性分析与本土化研究

在分析了以资源为基础的相对价值比率（Resource Based Relative Value Scale,RBRVS）的医师支付模式的发展背景、基本原理和计量模型的基础上,对其在我国公立医院薪酬改革中的可行性进行了分析,并结合大型综合性公立医院具体实践探讨了其在我国公立医院的本土化应用、存在的问题及应对措施。     

Structure-Thermodynamics-Antioxidant Activity Relationships of Selected Natural Phenolic Acids and Derivatives: An Experimental and Theoretical Evaluation

Phenolic acids and derivatives have potential biological functions, however, little is known about the structure-activity relationships and the underlying action mechanisms of these phenolic acids to date. Herein we investigate the structure-thermodynamics-antioxidant relationships of 20 natural phenolic acids and derivatives using DPPH^• scavenging assay, density functional theory calculations at the B3LYP/6-311++G(d,p) levels of theory, and quantitative structure-activity relationship (QSAR) modeling. Three main working mechanisms (HAT, SETPT and SPLET) are explored in four micro-environments (gas-phase, benzene, water and ethanol). Computed thermodynamics parameters (BDE, IP, PDE, PA and ETE) are compared with the experimental radical scavenging activities against DPPH^•. Available theoretical and experimental investigations have demonstrated that the extended delocalization and intra-molecular hydrogen bonds are the two main contributions to the stability of the radicals. The C = O or C = C in COOH, COOR, C = CCOOH and C = CCOOR groups, and orthodiphenolic functionalities are shown to favorably stabilize the specific radical species to enhance the radical scavenging activities, while the presence of the single OH in the ortho position of the COOH group disfavors the activities. HAT is the thermodynamically preferred mechanism in the gas phase and benzene, whereas SPLET in water and ethanol. Furthermore, our QSAR models robustly represent the structure-activity relationships of these explored compounds in polar media.     

Theoretical and Practical Aspects of Albumin Esterase Activity

Russian Journal of Bioorganic Chemistry - Unlike many other plasma proteins, albumin is barely glycosylated and plays an important role in maintaining the colloidal osmotic blood pressure; it can...     

Metachromasy: An Experimental and Theoretical Reevaluation

Non-chromotropic substances such as fibrin and gelatin and most tissue and cellular structures stain orthochromatically with internal dye concentrations of such metachromatic dyes as methylene blue and toluidine blue which, if in solution, would be metachromatic. Therefore, at ordinary levels of staining these substances depress the natural tendency of these dyes to change color. However, at elevated levels of dye-binding metachromasy eventually occurs. This phenomenon is explained on the basis of the distribution of dye-binding sites. In these substrates, by contrast with chromotropic substances, many binding sites are too far removed for dye interaction, consequently the interaction frequency can become high enough to produce a color change only as saturation of the available sites is approached. It is also shown that the destruction of color is a characteristic of metachromasy and that water molecules intercalated between approximated dye ions are responsible for the loss and change of color. A concept of metachromasy is proposed in which the interaction between water molecules and suitably approximated dye ions plays an essential role. The experimental studies are described against a background of the history and evolution of ideas on metachromasy. The literature is reviewed and reassessed particularly from the physicochemical viewpoint.     

An Evaluation of Sex-Age-Kill (SAK) Model Performance

ABSTRACT The sex-age-kill (SAK) model is widely used to estimate abundance of harvested large mammals, including white-tailed deer (Odocoileus virginianus). Despite a long history of use, few formal evaluations of SAK performance exist. We investigated how violations of the stable age distribution and stationary population assumption, changes to male or female harvest, stochastic effects (i.e., random fluctuations in recruitment and survival), and sampling efforts influenced SAK estimation. When the simulated population had a stable age distribution and λ > 1, the SAK model underestimated abundance. Conversely, when λ < 1, the SAK overestimated abundance. When changes to male harvest were introduced, SAK estimates were opposite the true population trend. In contrast, SAK estimates were robust to changes in female harvest rates. Stochastic effects caused SAK estimates to fluctuate about their equilibrium abundance, but the effect dampened as the size of the surveyed population increased. When we considered both stochastic effects and sampling error at a deer management unit scale the resultant abundance estimates were within ±121.9% of the true population level 95% of the time. These combined results demonstrate extreme sensitivity to model violations and scale of analysis. Without changes to model formulation, the SAK model will be biased when λ ≠ 1. Furthermore, any factor that alters the male harvest rate, such as changes to regulations or changes in hunter attitudes, will bias population estimates. Sex-age-kill estimates may be precise at large spatial scales, such as the state level, but less so at the individual management unit level. Alternative models, such as statistical age-at-harvest models, which require similar data types, might allow for more robust, broad-scale demographic assessments.     

Hypophosphatemia: A Practical Guide to Evaluation and Management

Phosphate plays a critical and diverse role in human physiology. In addition to its importance in skeletal mineralization, it is essential for energy homeostasis, enzyme function, and cell membrane integrity. These diverse functions of phosphate provide an explanation for the range of symptoms and clinical manifestations observed in patients with both acute and chronic causes of hypophosphatemia. Normal phosphate homeostasis involves several major systems, including the gastrointestinal tract, bones, and kidneys. Phosphate balance is maintained directly and indirectly by 1α,25-dihydroxyvitamin D₃, parathyroid hormone, and the osteocyte-derived phosphatonin fibroblast growth factor 23. This review discusses normal phosphate homeostasis, the clinical manifestations and causes of hypophosphatemia, and an approach to establish a diagnosis and appropriate management.