Intoxicação experimental em bovinos por Asclepias curassavica

Experiments with the aerial parts of Asclepias curassavica L., administered orally to bovines, were made. There are many references about its toxicity, but only few data on experimental poisoning by this plant in cattle. The green fresh plant was given to 38 young bovines, in different amounts and at different periods of the year; some animals received the plant more than once. Symptoms of poisoning, which were observed from 5 g/kg bodyweight on, consisted mainly in loss of appetite, diarrhea, tympany, submaxillar edema and cardiac irregularities; these symptoms lasted one to few days, and when the animals did not die, they always recovered in a short time. In the three animals that died during the experiments, the most important post-mortem finding was bloat. Histopathologic examinations did not reveal consistent and characteristic changes. There was no development of tolerance nor any accumulative effects due to the ingestion of the plant. Based on their field studies and on their experiments, the authors conclude that spontaneous poisoning by A. curassavica in cattle is not likely. The plant apparently is relatively unpalatable, animals do not eat it, even when hungry and on overgrazed pastures during the dry season.Foram realizados experimentos com as partes aéreas de Asclepias curassavica L., administrada a bovinos, por via oral. Há numerosas citações sobre a sua toxidez na literatura, porém, escassos dados sobre a intoxicação experimental pela ingestão dessa planta na espécie bovina. A planta verde recém-coletada foi administrada a 38 bovinos jovens desmamados, em diferentes quantidades e em diversas épocas do ano, em alguns animais repetidas vezes. A menor dose que provocou o aparecimento de sintomas de intoxicação por A. curassavica foi de 5 g/kg e a mais alta que não provocou sintomas foi de 10 g/kg. A menor dose que causou morte foi de 10 g/kg e a mais alta que não causou morte foi de 25 g/kg. Os sintomas de intoxicação consistiram em anorexia, diarreia, timpanismo, edema submaxilar e perturbações cardíacas. Eles variavam de um a poucos dias, havendo rápido restabelecimento quando não ocorria a morte. Nos três animais que morreram durante os experimentos, timpanismo foi o achado de necrópsia mais importante. Os exames histopatológicos não revelaram alterações constantes e características. Não houve desenvolvimento de tolerância nem efeito acumulativo pela ingestão da planta. Os autores concluem, baseando-se em suas investigações de campo e em seus experimentos, ser pouco provável a ocorrência de casos de intoxicação por ingestão espontânea de A. curassavica em bovinos. Aparentemente a planta possui baixa palatibilidade, pois os animais não a ingerem, mesmo com fome em pastos bem batidos, na época da seca

Tumor etmoidal enzoótico em bovinos no Estado do Rio de Janeiro

Ten cases of a tumor in cattle which arose at the ethmoid region were studied. These tumors occurred in the last seven years in the State of Rio de Janeiro. Eight of the ten cases were seen on one single farm. The neoplastic growth is identical with the "enzootic ethmoid tumor" described in Sweden, at the beginning of this century. The tumor had generally expansive growth, occupied the nasal cavities and penetrated the paranasal sinuses, and frequently caused eye protrusion. In three cases the lamina cribrosa was destroyed with consequent invasion of the cranial cavity by the tumor. The histological aspect varied in the ten cases, and even among the eight cases on the same farm. Two epidermoid carcinomas, four adenocarcinomas and four cases of carcinoma simplex were diagnosed.Foram estudados dez casos de tumor em bovinos com origem na região etmoidal, e que ocorreram nos últimos sete anos no Estado do Rio de Janeiro. Oito desses casos ocorreram em uma única fazenda. Esse processo neoplásico se revelou idêntico ao "tumor etmoidal enzoótico" descrito no começo do século na Suécia. Os tumores estudados tinham, em geral, crescimento expansivo, preenchendo a cavidade nasal, invadindo os seios paranasais e causando freqüentemente protrusão do globo ocular. Em três casos houve destruição do etmóide com invasão da cavidade craniana pelo blastoma. O aspecto histológico variou nos dez casos, também nos oito da mesma fazenda. Foram diagnosticados dois carcinomas epidermóides, quatro adenocarcinomas e em quatro casos carcinoma simples

Deoxyribonucleic acid homology of Azospirillum amazonense Magalhães et al. 1984 and emendation of the description of the genus Azospirillum.

The results of deoxyribonucleic acid homology experiments with the type strains of Azospirillum lipoferum, Azospirillum brasilense, and Azospirillum amazonense and 19 additional strains of A. amazonense confirmed that A. amazonense is a distinct new species. The description of the genus Azospirillum is emended to accommodate A. amazonense

Spheres and Prolate and Oblate Ellipsoids from an Analytical Solution of Spontaneous Curvature Fluid Membrane Model

An analytic solution for Helfrich spontaneous curvature membrane model (H. Naito, M.Okuda and Ou-Yang Zhong-Can, Phys. Rev. E {\bf 48}, 2304 (1993); {\bf 54}, 2816 (1996)), which has a conspicuous feature of representing the circular biconcave shape, is studied. Results show that the solution in fact describes a family of shapes, which can be classified as: i) the flat plane (trivial case), ii) the sphere, iii) the prolate ellipsoid, iv) the capped cylinder, v) the oblate ellipsoid, vi) the circular biconcave shape, vii) the self-intersecting inverted circular biconcave shape, and viii) the self-intersecting nodoidlike cylinder. Among the closed shapes (ii)-(vii), a circular biconcave shape is the one with the minimum of local curvature energy.Comment: 11 pages, 11 figures. Phys. Rev. E (to appear in Sept. 1999

Self-Consistent Thermal Accretion Disk Corona Models for Compact Objects: II. Application to Cygnus X-1

We apply our self-consistent accretion disk corona (ADC) model, with two different geometries, to the broad-band X-ray spectrum of the black hole candidate Cygnus X-1. As shown in a companion paper (Dove, Wilms, and Begelman), models where the Comptonizing medium is a slab surrounding the cold accretion disk cannot have a temperature higher than about 120 keV for optical depths greater than 0.2, resulting in spectra that are much softer than the observed 10-30 keV spectrum of Cyg X-1. In addition, the slab geometry models predict a substantial ``soft excess'' at low energies, a feature not observed for Cyg X-1, and Fe K\alpha fluorescence lines that are stronger than observed. Previous Comptonization models in the literature invoke a slab geometry with the optical depth \tau_T \gta 0.3 and the coronal temperature T_c \sim 150 keV, but they are not self-consistent. Therefore, ADC models with a slab geometry are not appropriate for explaining the X-ray spectrum of Cyg X-1. Models with a spherical corona and an exterior disk, however, predict much higher self-consistent coronal temperatures than the slab geometry models. The higher coronal temperatures are due to the lower amount of reprocessing of coronal radiation in the accretion disk, giving rise to a lower Compton cooling rate. Therefore, for the sphere+disk geometry, the predicted spectrum can be hard enough to describe the observed X-ray continuum of Cyg X-1 while predicting Fe fluorescence lines having an equivalent width of \sim 40 eV. Our best-fit parameter values for the sphere+disk geometry are \tau_T \approx 1.5 and T_c \approx 90 keV.Comment: 13 pages, Latex, 10 .eps figures, uses emulateapj.sty. To be published in ApJ, October 1, 1997, Vol. 48

Bistability in the actin cortex

Multi-color fluorescence imaging experiments of wave forming Dictyostelium cells have revealed that actin waves separate two domains of the cell cortex that differ in their actin structure and phosphoinositide composition. We propose a bistable model of actin dynamics to account for these experimental observation. The model is based on the simplifying assumption that the actin cytoskeleton is composed of two distinct network types, a dendritic and a bundled network. The two structurally different states that were observed in experiments correspond to the stable fixed points in the bistable regime of this model. Each fixed point is dominated by one of the two network types. The experimentally observed actin waves can be considered as trigger waves that propagate transitions between the two stable fixed points

Cell–Matrix De-Adhesion Dynamics Reflect Contractile Mechanics

Measurement of the mechanical properties of single cells is of increasing interest both from a fundamental cell biological perspective and in the context of disease diagnostics. In this study, we show that tracking cell shape dynamics during trypsin-induced de-adhesion can serve as a simple but extremely useful tool for probing the contractility of adherent cells. When treated with trypsin, both SW13−/− epithelial cells and U373 MG glioma cells exhibit a brief lag period followed by a concerted retraction to a rounded shape. The time–response of the normalized cell area can be fit to a sigmoidal curve with two characteristic time constants that rise and fall when cells are treated with blebbistatin and nocodazole, respectively. These differences can be attributed to actomyosin-based cytoskeletal remodeling, as evidenced by the prominent buildup of stress fibers in nocodazole-treated SW13−/− cells, which are also two-fold stiffer than untreated cells. Similar results observed in U373 MG cells highlights the direct association between cell stiffness and the de-adhesion response. Faster de-adhesion is obtained with higher trypsin concentration, with nocodazole treatment further expediting the process and blebbistatin treatment blunting the response. A simple finite element model confirms that faster contraction is achieved with increased stiffness

An Adhesion-Dependent Switch between Mechanisms That Determine Motile Cell Shape

Keratocytes are fast-moving cells in which adhesion dynamics are tightly coupled to the actin polymerization motor that drives migration, resulting in highly coordinated cell movement. We have found that modifying the adhesive properties of the underlying substrate has a dramatic effect on keratocyte morphology. Cells crawling at intermediate adhesion strengths resembled stereotypical keratocytes, characterized by a broad, fan-shaped lamellipodium, clearly defined leading and trailing edges, and persistent rates of protrusion and retraction. Cells at low adhesion strength were small and round with highly variable protrusion and retraction rates, and cells at high adhesion strength were large and asymmetrical and, strikingly, exhibited traveling waves of protrusion. To elucidate the mechanisms by which adhesion strength determines cell behavior, we examined the organization of adhesions, myosin II, and the actin network in keratocytes migrating on substrates with different adhesion strengths. On the whole, our results are consistent with a quantitative physical model in which keratocyte shape and migratory behavior emerge from the self-organization of actin, adhesions, and myosin, and quantitative changes in either adhesion strength or myosin contraction can switch keratocytes among qualitatively distinct migration regimes