920 research outputs found
Humoral and cellular immunopathology of hepatic and cardiac hamster-into-rat xenograft rejection: Marked stimulation of IgM<sup>++bright</sup>/IgD<sup>+dull</sup> splenic B cells
Normal Lewis rat serum contains antibodies (IgM > IgG) that bind to hamster leukocytes and endothelial cells. Transplantation of either the heart or liver from hamster rat results in release of hamster hematolymphoid cells from the graft, which lodge in the recipient spleen (cell migration), where recipient T- and B-cell populations initiate DNA synthesis within one day. There is marked stimulation of splenic IgM++(bright)/IgD+(dull) B cells in the marginal zone and red pulp, which account for 48% of the total splenic blast cell population by 4 days after liver transplantation. CD4+ predominant T-cell proliferation in the splenic periarterial lymphatic sheath and paracortex of peripheral lymph nodes occurs almost simultaneously. The effector phase of rejection in cardiac recipients is dominated by complement-fixing IgM antibodies, which increase daily and result in graft destruction in 3 to 4 days, even in animals treated with FK506. In liver recipients, combined antibody and cellular rejection, associated with graft infiltration by OX8+ natural killer, and fewer W3/25+ (CD4) lymphocytes, are responsible for graft failure in untreated recipients at 6 to 7 days. FK506 inhibits the T-cell response in liver recipients and significantly prolongs graft survival, but does not prevent the rise or deposition of IgM antibodies in the graft. However, a single injection of cyclophosphamide 10 days before transplantation effectively depletes the splenic IgM++(bright)/IgD+(dull) cells and in combination with FK506, results in 100% survival of both cardiac and hepatic xenografts for more than 60 days. Although extrapolation of morphological findings to functional significance is fraught with potential problems, we propose the following mechanisms of xenograft rejection. The reaction initially appears to involve primitive host defense mechanisms, including an IgM-producing subpopulation of splenic B cells and natural killer cells. Based on the reaction and distribution of OX8+ and W3/25+ cells, antibody dependent cell cytotoxicity and delayed-type hypersensitivity responses seem worthy of further investigation as possible effector mechanisms. Effective control of xenograft rejection is likely to require a dual pharmaceutical approach, one to contain T-cell immunity and another to blunt the primitive B-cell response
High temporal variability in the occurrence of consumer-resource interactions in ecological networks
Ecological networks are theoretical abstractions that represent ecological
communities. These networks are usually defined as static entities, in which
the occurrence of a particular interaction between species is considered fixed
despite the intrinsic dynamics of ecological systems. However, empirical
analysis of the temporal variation of trophic interactions is constrained by
the lack of data with high spatial, temporal, and taxonomic resolution. Here,
we evaluate the spatiotemporal variability of multiple consumer-resource
interactions of large marine networks. The tropic interactions of all of the
analyzed networks had low temporal persistence, which was well described by a
common exponential decay in the rank-frequency relationship of
consumer-resource interactions. This common pattern of low temporal persistence
was evident despite the dissimilarities of environmental conditions among
sites. Between-site rank correlations of frequency of occurrence of
interactions ranged from 0.59 to 0.73. After removing the interactions with
<50% frequency, the between-site correlations decreased to values between 0.60
and 0.28, indicating that low-frequency interactions accounted for the apparent
similarities between sites. Our results showed that the communities studied
were characterized by few persistent interactions and a large number of
transient trophic interactions. We suggest that consumer-resource temporal
asynchrony in addition to varying local environmental conditions and
opportunistic foraging could be among the mechanisms generating the observed
rank-frequency relationship of trophic interactions. Therefore, our results
question the analysis of ecological communities as static and persistent
natural entities and stress the need for strengthening the analysis of temporal
variability in ecological networks and long-term studies.Comment: 21 pages, 3 figure
Heat capacity study of BaFeAs: effects of annealing
Heat-capacity, X-ray diffraction, and resistivity measurements on a
high-quality BaFeAs sample show an evolution of the
magneto-structural transition with successive annealing periods. After a 30-day
anneal the resistivity in the (ab) plane decreases by more than an order of
magnitude, to 12 cm, with a residual resistance ratio 36; the
heat-capacity anomaly at the transition sharpens, to an overall width of less
than K, and shifts from 135.4 to 140.2 K. The heat-capacity anomaly in both the
as-grown sample and after the 30-day anneal shows a hysteresis of 0.15 K,
and is unchanged in a magnetic field H = 14 T. The X-ray and
heat-capacity data combined suggest that there is a first order jump in the
structural order parameter. The entropy of the transition is reported
Spin dynamics near a putative antiferromagnetic quantum critical point in Cu substituted BaFeAs and its relation to high-temperature superconductivity
We present the results of elastic and inelastic neutron scattering
measurements on non-superconducting
Ba(FeCu)As, a composition close to a
quantum critical point between AFM ordered and paramagnetic phases. By
comparing these results with the spin fluctuations in the low Cu composition as
well as the parent compound BaFeAs and superconducting
Ba(FeNi)As compounds, we demonstrate that paramagnon-like
spin fluctuations are evident in the antiferromagnetically ordered state of
Ba(FeCu)As, which is distinct from the AFM-like
spin fluctuations in the superconducting compounds. Our observations suggest
that Cu substitution decouples the interaction between quasiparticles and the
spin fluctuations. We also show that the spin-spin correlation length,
, increases rapidly as the temperature is lowered and find
scaling behavior, the hallmark of quantum criticality, at an
antiferromagnetic quantum critical point.Comment: 10 pages, 7 figure
What can metazoan parasites reveal about the taxonomy of Scomber japonicus Houttuyn in the coast of South America and Madeira Islands?
The metazoan parasites of four populations of the chub mackerel Scomber japonicus were
analysed from two localities in the Atlantic Ocean (Madeira Islands, Portugal, and Rio de
Janeiro, Brazil) and two localities in the Pacific Ocean (Callao, Peru, and Antofagasta, Chile),
collected during 2002 and 2003. A total of 373 fish specimens were studied and 34 metazoan
parasite species were obtained. Parasites identified from the populations of chub mackerel
studied could be separated into three categories: parasites with a wide distribution, present in
the Pacific and Atlantic, parasites proper of the Pacific Ocean and parasites proper of the
Atlantic Ocean. The analyses of some highly specific parasites of the genus Scomber (i.e.
monogeneans of the genus Kuhnia and didymozoid digeneans) strongly suggest the need for
a revision of the taxonomic status of chub mackerels from the Atlantic and Pacific coast of
America. The results demonstrated the usefulness of parasites as adequate tools to clarify the
taxonomic status of their hosts.We thank R. Poulin (University of Otago, New Zealand) for reading and commenting on an early draft of the manuscript. J.L.L. was supported by a fellowship (N° 200906-2005.4) of the Conselho Nacional de Desenvolvimento Cientı´fico e Tecnolo´ gico (CNPq) of Brazil for postdoctoral research in the Department of Zoology at the
University of Otago, New Zealand. G. Costa was supported by Portuguese Foundation
of Science and Technology, programme POCTI.info:eu-repo/semantics/publishedVersio
3D collagen migration patterns reveal a SMAD3-dependent and TGF-β1-independent mechanism of recruitment for tumour-associated fibroblasts in lung adenocarcinoma
The TGF-β1 transcription factor SMAD3 is epigenetically repressed in tumour-associated fibroblasts (TAFs) from lung squamous cell carcinoma (SCC) but not adenocarcinoma (ADC) patients, which elicits a compensatory increase in SMAD2 that renders SCC-TAFs less fibrotic. Here we examined the effects of altered SMAD2/3 in fibroblast migration and its impact on the desmoplastic stroma formation in lung cancer.We used a microfluidic device to examine descriptors of early protrusions and subsequent migration in 3D collagen gels upon knocking down SMAD2 or SMAD3 by shRNA in control fibroblasts and TAFs.High SMAD3 conditions as in shSMAD2 fibroblasts and ADC-TAFs exhibited a migratory advantage in terms of protrusions (fewer and longer) and migration (faster and more directional) selectively without TGF-β1 along with Erk1/2 hyperactivation. This enhanced migration was abrogated by TGF-β1 as well as low glucose medium and the MEK inhibitor Trametinib. In contrast, high SMAD2 fibroblasts were poorly responsive to TGF-β1, high glucose and Trametinib, exhibiting impaired migration in all conditions.The basal migration advantage of high SMAD3 fibroblasts provides a straightforward mechanism underlying the larger accumulation of TAFs previously reported in ADC compared to SCC. Moreover, our results encourage using MEK inhibitors in ADC-TAFs but not SCC-TAFs.© 2022. The Author(s)
Ex-ante assessment of integrated aquaculture-agriculture adoption and impact in Southern Malawi
There are increasing requirements for impact assessment by development partners in order to increase the accountability and effectiveness of research and development projects. Impact assessment research has been dominated by conventional economic methods. This context challenges agricultural research organizations to develop and apply alternative impact assessment methods incorporating economic, social, and environmental impact components. In this study, we use the Tradeoff Analysis for Multi-Dimensional Impact Assessment (TOA-MD) model to evaluate the impact of integrated aquaculture-agriculture (IAA) adoption in Malawi. The study demonstrated that with a minimal data set, the TOA-MD model can be applied to predict and assess the adoption rates of new technologies and practices as well as their economic and non-economic impacts
Relevance of mytilid shell microtopographies for fouling defence - a global comparison
Prevention of epibiosis is of vital importance for most aquatic organisms, which can have consequences for their ability to invade new areas. Surface microtopography of the shell periostracum has been shown to have antifouling properties for mytilid mussels, and the topography shows regional differences. This article examines whether an optimal shell design exists and evaluates the degree to which shell microstructure is matched with the properties of the local fouling community. Biomimics of four mytilid species from different regional provenances were exposed at eight different sites in both northern and southern hemispheres. Tendencies of the microtopography to both inhibit and facilitate fouling were detected after 3 and 6 weeks of immersion. However, on a global scale, all microtopographies failed to prevent fouling in a consistent manner when exposed to various fouling communities and when decoupled from other shell properties. It is therefore suggested that the recently discovered chemical anti-microfouling properties of the periostracum complement the anti-macrofouling defence offered by shell microtopography
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