Distribution of the major histocompatibility complex antigens in human and rat kidney

Distribution of the major histocompatibility complex antigens in human and rat kidney. We have compared the distribution of the major histocompatibility complex (MHC) antigens in human and rat kidney using monospecific antisera to class I and II antigens of the MHC. FITC/TRITC double immunofluorescence was used to demonstrate these antigens in frozen sections and the Staphylococcus aureus Cowan I rosette assay on the cell surface. In both species, the MHC antigens were prominently present on the passenger leukocytes. Immunofluorescence analysis of human kidney demonstrated that the class I, β2-microglobulin (β2m), and class II antigens were present in the vascular endothelial cells and class I antigens in the renal tubular cells. The Staphylococcus assay demonstrated that these antigens were also exposed on the respective cell surfaces. In clear contrast, in the rat, class I, the β2m, and class II antigens were absent from the kidney vascular endothelium of large vessels and intertubular capillaries; however, large amounts of class II antigens were seen inside the proximal renal tubular cells. The Staphylococcus assay indicated that none or very little of these antigens were exposed on the kidney parenchymal cell surface. These differences may explain why rat renal transplants are relatively non-immunogenic and easily accepted, whereas human renal transplant recipients must be immunosuppressed ad infinitum.Distribution des antigènes du complexe d'histocompatibilité principal du rein d'homme et de rat. Nous avons comparé la distribution des antigènes du complexe d'histocompatibilité principal (MHC) dans du rein d'homme et de rat en utilisant des antisérums monospécifiques des antigènes des classes I et II du MHC. Une double immunofluorescence FITC/TRITC a été utilisée pour démontrer ces antigènes dans des sections congelées et le dosage des rosettes de Staphylocoque doré Cowan I pour les démontrer à la surface cellulaire. Dans les deux espèces, les antigènes MHC étaient essentiellement présents sur les leucocytes de passage. L'analyse en immunofluorescence de rein humain a démontré que les antigènes de classe I, 1 β2-microglobuline (β2m) et de classe II étaient présents dans les cellules endothéliales vasculaires, et ceux de classe I dans les cellules tubulaires rénales. Le dosage Staphylocoque a démontré que ces antigènes étaient également exposés sur les surfaces cellulaires respectives. De facon clairement opposée, chez le rat, les antigènes de classe I, 1 β2m et de classe II étaient absents de l'endothélium vasculaire rénal des gros vaisseaux et des capillaires intertubulaires; cependant, de grandes quantités d'antigènes de classe II étaient visibles à l'intérieur des cellules tubulaires rénales proximales. L'essai Staphylocoque a indiqué qu'aucun ou très peu de ces antigènes étaient exposés à la surface des cellules parenchymateuses rénales. Ces différences pourraient expliquer pourquoi les greffons rénaux de rat sont relativement non immunogènes et facilement tolérés, alors que les receveurs de transplants rénaux humains doivent être immunodéprimés indéfiniment

Good policies for bad governments: behavioral political economy

Politicians and policymakers are prone to the same biases as private citizens. Even if politicians are rational, little suggests that they have altruistic interests. Such concerns lead us to be wary of proposals that rely on benign governments to implement interventionist policies that "protect us from ourselves." The authors recommend paternalism that recognizes both the promise and threat of activist government. They support interventions that channel behavior without taking away consumers' ability to choose for themselves. Such "benign paternalism" can lead to very dramatic behavioral changes. But benign paternalism does not give government true authority to control our lives and does not give private agents an incentive to reject such authority through black markets and other corrosive violations of the rule of law. The authors discuss five examples of policy interventions that will generate significant welfare gains without reducing consumer liberties. They believe that all policy proposals should be viewed with healthy skepticism. No doctor would prescribe a drug that only worked in theory. Likewise, economic policies should be tested with small-scale field experiments before they are adopted.Macroeconomics ; Economics ; Economic policy

Mass Extinctions vs. Uniformitarianism in Biological Evolution

It is usually believed that Darwin's theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of coevolving species. The models exhibit self-organized criticality and describe some general features of the extinction pattern in the fossil record.Comment: 17 pages uuencoded with style file lamuphys.sty. 9 figures not included but can be obtained via [email protected]. to appear in ``Physics of Biological Systems'' Lecture Notes in Physics (Springer-Verlag, Heidelberg , 1996

Letters from the New World: about Copi’s La cité des rats

La novela epistolar La cité des rats comienza con una advertencia: el autor y el editor del texto invitan a los amantes de las normas consensuadas del “escribir bien” a abandonar el libro y regresar a sus lecturas favoritas. Esa nota inicial no sólo atañe a aspectos estilísticos, sino que tiene también implicaciones ideológicas. En efecto, la novela desafía la ética y la estética de los discursos humanistas mediante lo que César Aira ha denominado “antropología del continuo”, procedimiento con el que la novela transfigura el universo en miniatura de las ratas, tierno y domesticado, en un nuevo mundo hecho de umbrales y territorios liminares. Nos proponemos realizar una lectura de esos pasajes para investigar los modos en que la escritura de Copi hace emerger, en el espacio que une y separa el universo animal y el humano, la fuerza desestabilizadora de lo imaginario.The epistolary novel La cité des Rats begins with a warning: the author and the editor of the text invites the lovers of the consensual norms of “good writing” to abandon the book and return to their favorite readings. That initial notice not only regards stylistic aspects, but it has also some ideological implications. In fact, the novel defies the ethics and aesthetics of humanist speeches through what César Aira has called “Anthropology of the continuum”, a procedure with which the novel transfigures the miniature universe of rats, tender and tame, in a new world made of thresholds and liminal territories. We intend to analyze those passages in order to investigate the ways in which Copi’s writing makes emerge –in the space that joins and separates the animal and the human universe– the destabilizing force of the imaginary.Fil: Yelin, Julieta Rebeca. Universidad Nacional de Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

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Dose-response relationship and low dose extrapolatioin in chemical carcinogenesis

Data supporting various dose-response relationships in chemical carcinogenesis are summarized. General principles are derived to explain the relationships between exposure dose, DNA adduct level, induction of genetic changes, and tumor incidence. Some mechanistic aspects of epigenetic carcinogens (stimulation of cell division and maldifferentiation) are analyzed in a similar way. In a homogeneous population, non-linearities are frequent. They are due to phenomena of induction or saturation of enzymatic activities and to the multi-step nature of carcinogenesis: if a carcinogen accelerates more than one step, the superposition of the dose-response curves for the individual steps can result in an exponential relationship. A fourth power of the dose was the maximum seen in animals (formaldehyde). At the lowest dose levels, a proportionality between dose and tumor induction is postulated independent of the mechanism of action if the carcinogen accelerates the endogenous process responsible for spontaneous tumor formation. Low-dose thresholds are expected only for situations where the carcinogen acts in a way that has no endogenous counterpart. Epidemlological studies in humans show linear dose-response curves in all but two investigations. The difference from the strongly non-linear slopes seen in animal studies could be due to the heterogeneity of the human population: if the individual sensitivity to a carcinogen is governed by a large number of genetic and life-style factors, the non-linearities will tend to cancel each other out and the dose-response curve becomes ‘quasi-linear

Your Pet

Babes in Toyland iPad apps, toys for the lazy cat owner, indestructible rubber bones, hide-and-seek games for small pets—HSUS staff pets review the best holiday stocking stuffers for the furry set