893 resultados para Load bearing
Resumo:
CONTEXT: A broad spectrum of GnRH-deficient phenotypes has been identified in individuals with both mono- and biallelic GNRHR mutations. OBJECTIVE: The objective of the study was to determine the correlation between the severity of the reproductive phenotype(s) and the number and functional severity of rare sequence variants in GNRHR. SUBJECTS: Eight hundred sixty-three probands with different forms of GnRH deficiency, 46 family members and 422 controls were screened for GNRHR mutations. The 70 subjects (32 patients and 38 family members) harboring mutations were divided into four groups (G1-G4) based on the functional severity of the mutations (complete or partial loss of function) and the number of affected alleles (monoallelic or biallelic) with mutations, and these classes were mapped on their clinical phenotypes. RESULTS: The prevalence of heterozygous rare sequence variants in GNRHR was significantly higher in probands vs. controls (P < 0.01). Among the G1-G3 groups (homozygous subjects with successively decreasing severity and number of mutations), the hypogonadotropic phenotype related to their genetic load. In contrast, subjects in G4, with only monoallelic mutations, demonstrated a greater diversity of clinical phenotypes. CONCLUSIONS: In patients with GnRH deficiency and biallelic mutations in GNRHR, genetic burden defined by severity and dose is associated with clinical phenotype. In contrast, for patients with monoallelic GNRHR mutations this correlation does not hold. Taken together, these data indicate that as-yet-unidentified genetic and/or environmental factors may combine with singly mutated GNRHR alleles to produce reproductive phenotypes.
Resumo:
Tissue protein hypercatabolism (TPH) is a most important feature in cancer cachexia, particularly with regard to the skeletal muscle. The rat ascites hepatoma Yoshida AH-130 is a very suitable model system for studying the mechanisms involved in the processes that lead to tissue depletion, since it induces in the host a rapid and progressive muscle waste mainly due to TPH (Tessitore, L., G. Bonelli, and F. M. Baccino. 1987. Biochem. J. 241:153-159). Detectable plasma levels of tumor necrosis factor-alpha associated with marked perturbations in the hormonal homeostasis have been shown to concur in forcing metabolism into a catabolic setting (Tessitore, L., P. Costelli, and F. M. Baccino. 1993. Br. J. Cancer. 67:15-23). The present study was directed to investigate if beta 2-adrenergic agonists, which are known to favor skeletal muscle hypertrophy, could effectively antagonize the enhanced muscle protein breakdown in this cancer cachexia model. One such agent, i.e., clenbuterol, indeed largely prevented skeletal muscle waste in AH-130-bearing rats by restoring protein degradative rates close to control values. This normalization of protein breakdown rates was achieved through a decrease of the hyperactivation of the ATP-ubiquitin-dependent proteolytic pathway, as previously demonstrated in our laboratory (Llovera, M., C. García-Martínez, N. Agell, M. Marzábal, F. J. López-Soriano, and J. M. Argilés. 1994. FEBS (Fed. Eur. Biochem. Soc.) Lett. 338:311-318). By contrast, the drug did not exert any measurable effect on various parenchymal organs, nor did it modify the plasma level of corticosterone and insulin, which were increased and decreased, respectively, in the tumor hosts. The present data give new insights into the mechanisms by which clenbuterol exerts its preventive effect on muscle protein waste and seem to warrant the implementation of experimental protocols involving the use of clenbuterol or alike drugs in the treatment of pathological states involving TPH, particularly in skeletal muscle and heart, such as in the present model of cancer cachexia.
Resumo:
We combined structural analysis, thermobarometry and oxygen isotope geochemistry to constrain the evolution of kyanite and/or andalusite-bearing quartz veins from the amphibolite facies metapelites of the Simano nappe, in the Central Alps of Switzerland. The Simano nappe records a complex polyphase tectonic evolution associated with nappe stacking during Tertiary Alpine collision (D1). The second regional deformation phase (132) is responsible for the main penetrative schistosity and mineral lineation, and formed during top-to-the-north thrusting. During the next stage of deformation (D3) the aluminosilicate-bearing veins formed by crystallization in tension gashes, in tectonic shadows of boudins, as well as along shear bands associated with top-to-the-north shearing. D2 and D3 are coeval with the Early Miocene metamorphic peak, characterised by kyanite + staurolite + garnet + biotite assemblages in metapelites. The peak pressure (P) and temperature (T) conditions recorded are constrained by multiple-equilibrium thermobarometry at 630 +/- 20 degrees C and 8.5 +/- 1 kbar (similar to 27 km depth), which is in agreement with oxygen isotope thermometry indicating isotopic equilibration of quartz-kyanite pairs at 670 +/- 50 degrees C. Quartz-kyanite pairs from the aluminosilicate-bearing quartz veins yield equilibration temperatures of 645 +/- 20 degrees C, confirming that the veins formed under conditions near metamorphic peak. Quartz and kyanite from veins and the surrounding metapelites have comparable isotopic compositions. Local intergranular diffusion in the border of the veins controls the mass-transfer and the growth of the product assemblage, inducing local mobilization of SiO2 and Al2O3. Andalusite is absent from the host rocks, but it is common in quartz veins, where it often pseudomorphs kyanite. For andalusite to be stable at T-max, the pressure in the veins must have been substantially lower than lithostatic. An alternative explanation consistent with structural observations would be inheritance by andalusite of the kyanite isotopic signature during polymorphic transformation after the metamorphic peak.
Resumo:
During timber exploitation in forest stands harvesting machines pass repeatedly along the same track and can cause soil compaction, which leads to soil erosion and restricted tree root growth. The level of soil compaction depends on the number of passes and weight of the wood load. This paper aimed to evaluate soil compaction and eucalyptus growth as affected by the number of passes and wood load of a forwarder. The study was carried out in Santa Maria de Itabira county, Minas Gerais State - Brazil, on a seven-year-old eucalyptus stand planted on an Oxisol. The trees were felled by chainsaw and manually removed. Plots of 144 m² (four rows 12 m long in a 3 x 2 m spacing) were then marked off for the conduction of two trials. The first tested the traffic intensity of a forwarder which weighed 11,900 kg and carried 12 m³ wood (density of 480 kg m-3) and passed 2, 4, and 8 times along the same track. In the second trial, the forwarder carried loads of 4, 8, and 12 m³ of wood, and the machine was driven four times along the same track. In each plot, the passes affected four rows. Eucalyptus was planted in 30 x 30 x 30 cm holes on the compacted tracks. The soil in the area is clayey (470 clay and 440 g kg-1 sand content) and at depths of 0-5 cm and 5-10 cm, respectively, soil organic carbon was 406 and 272 g kg-1 and the moisture content during the trial 248 and 249 g kg-1. These layers were assessed for soil bulk density and water-stable aggregates. The infiltration rate was measured by a cylinder infiltrometer. After 441 days the measurements were repeated, with additional analyses of: soil organic carbon, total nitrogen, N-NH4+, N-NO3-, porosity, and penetration resistance. Tree height, stem diameter, and stem dry matter were measured. Forwarder traffic increased soil compaction, resistance to penetration and microporosity while it reduced the geometric mean diameter, total porosity, macroporosity and infiltration rate. Stem dry matter yield and tree height were not affected by soil compaction. Two passes of the forwarder were enough to cause the disturbances at the highest levels. The compaction effects were still persistent 441 days after forwarder traffic.
Resumo:
Cell motility is an essential process that depends on a coherent, cross-linked actin cytoskeleton that physically coordinates the actions of numerous structural and signaling molecules. The actin cross-linking protein, filamin (Fln), has been implicated in the support of three-dimensional cortical actin networks capable of both maintaining cellular integrity and withstanding large forces. Although numerous studies have examined cells lacking one of the multiple Fln isoforms, compensatory mechanisms can mask novel phenotypes only observable by further Fln depletion. Indeed, shRNA-mediated knockdown of FlnA in FlnB¿/¿ mouse embryonic fibroblasts (MEFs) causes a novel endoplasmic spreading deficiency as detected by endoplasmic reticulum markers. Microtubule (MT) extension rates are also decreased but not by peripheral actin flow, because this is also decreased in the Fln-depleted system. Additionally, Fln-depleted MEFs exhibit decreased adhesion stability that appears in increased ruffling of the cell edge, reduced adhesion size, transient traction forces, and decreased stress fibers. FlnA¿/¿ MEFs, but not FlnB¿/¿ MEFs, also show a moderate defect in endoplasm spreading, characterized by initial extension followed by abrupt retractions and stress fiber fracture. FlnA localizes to actin linkages surrounding the endoplasm, adhesions, and stress fibers. Thus we suggest that Flns have a major role in the maintenance of actin-based mechanical linkages that enable endoplasmic spreading and MT extension as well as sustained traction forces and mature focal adhesions.
Resumo:
The impact of wood loads on bulk density and preconsolidation pressure and of harvester and forwarder traffic on rut depth, bulk density and preconsolidation pressure of two Ultisols were examined in this study. Our objective was to quantify the threshold beyond which significant soil compaction and rutting would occur. This study was carried out in the county of Eunápolis, state of Bahia, Brazil, (16 º 23 ' 17 '' S and 39 º 10 ' 06 '' W; altitude 80 m asl) in two Ultisols (PAd2 and PAd3) with different texture classes, in experimental areas with eucalypt plantation. The study involved measurements at the wood load site and machine driving at specific locations in the forest during logging operations. The treatments consisted of one harvester pass and, 8, 16 and 40 passes of a fully loaded forwarder. Thresholds were established based on the rut depth and percentage of preconsolidation pressure values in the region of additional soil compaction defined in the bearing capacity model. The percentage of soil samples with values of preconsolidation pressure in the region of additional soil compaction indicated a greater susceptibility of PAd3 than of PAd2 to soil compaction. The threshold levels established here based on preconsolidation pressure and rut depth indicated that no more than eight forwarder passes should be allowed in loading operations in order to minimize soil compaction.
Resumo:
Several European telecommunications regulatory agencies have recently introduced a fixed capacity charge (flat rate) to regulate access to the incumbent's network. The purpose of this paper is to show that the optimal capacity charge and the optimal access-minute charge analysed by Armstrong, Doyle, and Vickers (1996) have a similar structure and imply the same payment for the entrant. I extend the analysis tothe case where there is a competitor with market power. In this case, the optimalcapacity charge should be modified to avoid that the entrant cream-skims the market,fixing a longer or a shorter peak period than the optimal. Finally, I consider a multiproduct setting, where the effect of the product differentiation is exacerbated.
Resumo:
The El Soplao site is a recently-discovered Early Albian locality of the Basque-Cantabrian Basin (northern Spain) that has yielded a number of amber pieces with abundant bioinclusions. The amber-bearing deposit occurs in a non-marine to transitional marine siliciclastic unit (Las Peñosas Formation) that is interleaved within a regressive-transgressive, carbonate-dominated Lower Aptian-Upper Albian marine sequence. The Las Peñosas Formation corresponds to the regressive stage of this sequence and in its turn it splits into two smaller regressive-transgressive cycles. The coal and amber-bearing deposits occur in deltaic-estuarine environments developed during the maximum regressive episodes of these smaller regressive-transgressive cycles. The El Soplao amber shows Fourier Transform Infrared Spectroscopy spectra similar to other Spanish Cretaceous ambers and it is characterized by the profusion of sub-aerial, stalactite-like flows. Well-preserved plant cuticles assigned to the conifer genera Frenelopsis and Mirovia are abundant in the beds associated with amber. Leaves of the ginkgoalean genera Nehvizdya and Pseudotorellia also occur occasionally. Bioinclusions mainly consist of fossil insects of the orders Blattaria, Hemiptera, Thysanoptera, Raphidioptera, Neuroptera, Coleoptera, Hymenoptera and Diptera, although some spiders and spider webs have been observed as well. Some insects belong to groups scarce in the fossil record, such as a new morphotype of the wasp Archaeromma (of the family Mymarommatidae) and the biting midge Lebanoculicoides (of the monogeneric subfamily Lebanoculicoidinae). This new amber locality constitutes a very significant finding that will contribute to improving the knowledge and comprehension of the Albian non-marine paleoarthropod fauna.
Resumo:
BACKGROUND: Normocalcemic primary hyperparathyroidism (PHPT-N) is a condition that may have similar long-term implications to primary hyperparathyroidism (PHPT); however, differential diagnosis and treatment for parathyroid disorders are not clearly defined. We investigated the effect of an oral peptone and an oral calcium load on calcium-regulating hormones in PHPT-N compared with PHPT and healthy controls to provide a new potential diagnostic tool. DESIGN: Case-control study. METHODS: We evaluated serum gastrin, PTH, ionized calcium, and phosphate responses to oral calcium (1 g) and peptone (10 g) load in 22 PHPT and 20 PHPT-N patients matched for PTH serum values. Moreover, 30 healthy subjects were enrolled as controls. In 12 patients for each group, we also performed the oral peptone test adding aluminum hydroxide (AH) to suppress phosphate absorption. RESULTS: In PHPT patients, PTH increased significantly 30 min after the oral peptone load, while no significant increase was found in PHPT-N and controls. After oral calcium load, PTH remained stable in PHPT while it decreased dramatically in PHPT-N patients, and ionized calcium increased significantly in each of the three groups. Peptones plus AH induced a blunted PTH increase in the three groups. CONCLUSIONS: Considering the marked difference in PTH response elicited by peptones in PHPT compared with PHPT-N, we suggest that the oral peptone test could be added to the diagnostic evaluation of PHPT patients. In case of absent response to peptones, patients should have their serum calcium levels assessed twice a year in accordance with recent guidelines.
Resumo:
Inbreeding avoidance is often invoked to explain observed patterns of dispersal, and theoretical models indeed point to a possibly important role. However, while inbreeding load is usually assumed constant in these models, it is actually bound to vary dynamically under the combined influences of mutation, drift, and selection and thus to evolve jointly with dispersal. Here we report the results of individual-based stochastic simulations allowing such a joint evolution. We show that strongly deleterious mutations should play no significant role, owing to the low genomic mutation rate for such mutations. Mildly deleterious mutations, by contrast, may create enough heterosis to affect the evolution of dispersal as an inbreeding-avoidance mechanism, but only provided that they are also strongly recessive. If slightly recessive, they will spread among demes and accumulate at the metapopulation level, thus contributing to mutational load, but not to heterosis. The resulting loss of viability may then combine with demographic stochasticity to promote population fluctuations, which foster indirect incentives for dispersal. Our simulations suggest that, under biologically realistic parameter values, deleterious mutations have a limited impact on the evolution of dispersal, which on average exceeds by only one-third the values expected from kin-competition avoidance.
Resumo:
This guide provides a summary of the factors and design theories that should be considered when designing dowel load transfer systems for concrete pavement systems (including dowel basket design and fabrication) and presents recommendations for widespread adoption (i.e., standardization). Development of the guide was sponsored by the National Concrete Consortium with the goal of helping practitioners develop and implement dowel load transfer designs based on knowledge about current research and best practices.
Resumo:
Knowledge of the quantitative genetics of resistance to parasitism is key to appraise host evolutionary responses to parasite selection. Here, we studied effects of common origin (i.e. genetic and pre-hatching parental effects) and common rearing environment (i.e. post-hatching parental effects and other environment effects) on variance in ectoparasite load in nestling Alpine swifts (Apus melba). This colonial bird is intensely parasitized by blood sucking louse-flies that impair nestling development and survival. By cross-fostering half of the hatchlings between pairs of nests, we show strong significant effect of common rearing environment on variance (90.7% in 2002 and 90.9% in 2003) in the number of louse-flies per nestling and no significant effect of common origin on variance in the number of louse-flies per nestling. In contrast, significant effects of common origin were found for all the nestling morphological traits (i.e. body mass, wing length, tail length, fork length and sternum length) under investigation. Hence, our study suggests that genetic and pre-hatching parental effects play little role in the distribution of parasites among nestling Alpine swifts, and thus that nestlings have only limited scope for evolutionary responses against parasites. Our results highlight the need to take into consideration environmental factors, including the evolution of post-hatching parental effects such as nest sanitation, in our understanding of host-parasite relationships.
Resumo:
During an infection the antigen-nonspecific memory CD8 T cell compartment is not simply an inert pool of cells, but becomes activated and cytotoxic. It is unknown how these cells contribute to the clearance of an infection. We measured the strength of T cell receptor (TCR) signals that bystander-activated, cytotoxic CD8 T cells (BA-CTLs) receive in vivo and found evidence of limited TCR signaling. Given this marginal contribution of the TCR, we asked how BA-CTLs identify infected target cells. We show that target cells express NKG2D ligands following bacterial infection and demonstrate that BA-CTLs directly eliminate these target cells in an innate-like, NKG2D-dependent manner. Selective inhibition of BA-CTL-mediated killing led to a significant defect in pathogen clearance. Together, these data suggest an innate role for memory CD8 T cells in the early immune response before the onset of a de novo generated, antigen-specific CD8 T cell response.
Resumo:
This report presents a review of literature on geosynthetic reinforced soil (GRS) bridge abutments, and test results and analysis from two field demonstration projects (Bridge 1 and Bridge 2) conducted in Buchanan County, Iowa, to evaluate the feasibility and cost effectiveness of the use of GRS bridge abutments on low-volume roads (LVRs). The two projects included GRS abutment substructures and railroad flat car (RRFC) bridge superstructures. The construction costs varied from $43k to $49k, which was about 50 to 60% lower than the expected costs for building a conventional bridge. Settlement monitoring at both bridges indicated maximum settlements ≤1 in. and differential settlements ≤ 0.2 in transversely at each abutment, during the monitoring phase. Laboratory testing on GRS fill material, field testing, and in ground instrumentation, abutment settlement monitoring, and bridge live load (LL) testing were conducted on Bridge 2. Laboratory test results indicated that shear strength parameters and permanent deformation behavior of granular fill material improved when reinforced with geosynthetic, due to lateral restraint effect at the soilgeosynthetic interface. Bridge LL testing under static loads indicated maximum deflections close to 0.9 in and non-uniform deflections transversely across the bridge due to poor load transfer between RRFCs. The ratio of horizontal to vertical stresses in the GRS fill was low (< 0.25), indicating low lateral stress on the soil surrounding GRS fill material. Bearing capacity analysis at Bridge 2 indicated lower than recommended factor of safety (FS) values due to low ultimate reinforcement strength of the geosynthetic material used in this study and a relatively weak underlying foundation layer. Global stability analysis of the GRS abutment structure revealed a lower FS than recommended against sliding failure along the interface of the GRS fill material and the underlying weak foundation layer. Design and construction recommendations to help improve the stability and performance of the GRS abutment structures on future projects, and recommendations for future research are provided in this report.