The potential role of photoelectron microscopy in the analysis of biological surfaces

12 pagesThe photoelectric effect provides the basis for an imaging technique useful for the study of biological surfaces. The photoelectron microscope (PEM) employs a UV lamp to photoeject electrons from the specimen surface. The electrons are then accelerated and imaged using electron optics. Photoelectron micrographs often resemble scanning electron micrographs, but the origin of contrast is different and these two techniques are complementary. Scanning Electron Microscopy (SEM) is unsurpassed in applications where specimens have pronounced relief or where elemental analysis is required. The advantages of PEM are a new origin of contrast, high sensitivity to fine topographical detail, short depth of information, and low specimen conductivity requirements. Photoelectron Images of model systems, cell surfaces and cytoskeletal elements have been obtained

Immunophotoelectron Microscopy: The Electron Optical Analog of Immunofluorescence Microscopy

5 pagesThe electron optical analog of immunofluo rescence microscopy combines three developments: (i) photoelectron microscopy to produce a high-resolution image of ex posed components of the cell, (jQ site-specific antibodies, and (iii) photoemissive markers coupled to the antibodies to make the distribution of sites visible. This approach, in theory, pro vides a way to extend the useful immunofluorescence micros copy technique to problems requiring much higher resolution. The resolution limit of fluorescence microscopy is limited to about 200 nm by the wavelength of the light used to form the image, whereas in photoelectron microscopy the image is formed by electrons (current resolution: 10-20 nm; theoretical limit: 5 nm or better depending on the electron optics). As a test system, cytoskeletons of CV-1 epithelial cells were pre pared under conditions that preserve microtubules, and the microtubule networks were visualized by both indirect immu nofluorescence and immunophotoelectron microscopy using colloidal gold coated with antibodies. Colloidal gold serves as a label for immunophotoelectron microscopy, providing en hanced photoemission from labeled cellular components so that they stand out against the darker background of the re maining unlabeled structures. In samples prepared for both immunofluorescence and immunophotoelectron microscopy, individual microtubules in the same cells were visualized by both techniques. The photoemissionof the colloidal gold mark ers is sufficiently high that the microtubules are easily recog nized without reference to the immunofluorescence micro graphs, indicating that this approach can be used, in combina tion with antibodies, to correlate structure and function in cell biological studies

Detection of siRNA administered to cells and animals by using a fluorescence intensity distribution analysis polarization system

Small interfering RNA (siRNA) has excellent pharmacological features and is expected to be used for therapeutic drug development. To this end, however, new RNA technology needs to be established so that extremely small amounts (less than 1 pmol) of siRNA can be detected in organs of experimental animals and in human blood to facilitate pharmacokinetics studies. An important feature is that this new technology is not dependent on radioisotopes and can detect siRNA molecules identical to those used for drug development in preclinical tests with experimental animals or in clinical tests with humans. We report a convenient method that can detect small amounts of siRNA. The method uses high-power confocal microscopic analysis of fluorescence polarization in DNA probes that are bound to one of the strands of siRNA and directly quantitates the copy number of siRNA molecule after extraction from specimens. A pharmacokinetic study to examine the blood retention time of siRNA/cationic liposomes in mice showed that this straightforward method is consistent with the other reverse transcriptase polymerase chain reaction amplification-based method. We believe that the entire process is simple and applicable for a high-throughput analysis, which provides excellent technical support for fundamental research on RNA interference and development of siRNA drugs

The effects of aging and maternal protein restriction during lactation on thymic involution and peripheral immunosenescence in adult mice.

Environmental factors such as nutrition during early life can influence long-term health, a concept termed developmental programming. Initial research was focused towards the effects on metabolic health but more recent studies have demonstrated effects on parameters such as lifespan and immunity. In this study we report that maternal protein restriction during lactation in mice, that is known to prolong lifespan, slows aging of the central and peripheral immune systems. Offspring of dams fed a postnatal low-protein (PLP) diet during lactation had a significant increase in thymic cellularity and T cell numbers across their lifespan compared to controls, and a less marked age-associated decrease in thymocyte cluster of differentiation (CD) 3 expression. PLP animals also demonstrated increased relative splenic cellularity, increased naïve: memory CD4+ and CD8+ T cell ratios, increased staining and density of germinal centres, and decreased gene expression of p16 in the spleen, a robust biomarker of aging. A slower rate of splenic aging in PLP animals would be expected to result in decreased susceptibility to infection and neoplasia. In conclusion nutritionally-induced slow postnatal growth leads to delayed aging of the adaptive immune system, which may contribute towards the extended lifespan observed in these animals.This work was supported by the BBSRC and the MRC. SEO is funded by the University of Cambridge MRC Metabolic Diseases Unit (MRC_MC_UU_12012/4).This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Impact Journals

COVID-19, systemic crisis, and possible implications for the wild meat trade in sub-Saharan Africa

Wild animals play an integral and complex role in the economies and ecologies of many countries across the globe, including those of West and Central Africa, the focus of this policy perspective. The trade in wild meat, and its role in diets, have been brought into focus as a consequence of discussions over the origins of COVID-19. As a result, there have been calls for the closure of China’s “wet markets”; greater scrutiny of the wildlife trade in general; and a spotlight has been placed on the potential risks posed by growing human populations and shrinking natural habitats for animal to human transmission of zoonotic diseases. However, to date there has been little attention given to what the consequences of the COVID-19 economic shock may be for the wildlife trade; the people who rely on it for their livelihoods; and the wildlife that is exploited. In this policy perspective, we argue that the links between the COVID-19 pandemic, rural livelihoods and wildlife are likely to be more complex, more nuanced, and more far-reaching, than is represented in the literature to date. We develop a causal model that tracks the likely implications for the wild meat trade of the systemic crisis triggered by COVID-19. We focus on the resulting economic shockwave, as manifested in the collapse in global demand for commodities such as oil, and international tourism services, and what this may mean for local African economies and livelihoods. We trace the shockwave through to the consequences for the use of, and demand for, wild meats as households respond to these changes. We suggest that understanding and predicting the complex dynamics of wild meat use requires increased collaboration between environmental and resource economics and the ecological and conservation sciences

Corruption and the WTO Legal System

The World Trade Organization has no substantive rules directly addressing corruption in trade relations. There are, however, numerous legal provisions in the various WTO texts that offer indirect support to traders facing corrupt trade administrators. Whether these provisions are sufficient to address the bulk of trade-related corruption is questionable, given the narrow range of corrupt practices that are affected by these, mainly procedural, obligations. This article sets out a framework for further research into the question of how corruption affects trade liberalization, and puts forth a suggestion for how the WTO could take a step towards remedying its avoidance of the topic of corruption while not exceeding its functional scope of regulating trade relations among Members