985 research outputs found
In vitro culture of Fasciola hepatica and the immunology associated with the metabolic products of the trematode
This work is presented in three Sections, concerned respectively
with the in vitro maintenance of Fasciola hepatica, production and
properties of the metabolic antigens of F. hepatica and immunisation
of the mammalian host with these antigens.In Section One a number of studies were made on the in vitro
maintenance of adult F. hepatica, with a view to establishing a
routine method for maintaining large numbers of flukes together, to
facilitate subsequent studies on the antigenic properties of their
metabolic products. A detailed description is given of a continuousflow
culture apparatus for the axenic in vitro maintenance of groups
of adult flukes. The suitability of various media and culture
conditions was assessed by measuring the rate of production of
ammonia, an end-product of trematode protein metabolism.It was shown that when the medium consisted of a simple balanced
salts solution (modified Earle's salts) flukes showed 100% survival
over a five day culture period, but the rate of ammonia production
declined rapidly during the initial three days. However, when the
medium was supplemented with increasing amounts of serum, the rate of
ammonia production was maintained at levels more closely approaching
the initial level. Medium 199 (a multi-component tissue culture medium)
was shown to be slightly more favourable than the simple balanced
salts solution, but less so than those media which contained high
proportions of serum. It was shown that inclusion of clotted blood
in the medium had no effect on ammonia production, but an increased
flow-rate of the culture medium was associated with the output of
significantly greater amounts of ammonia, presumably due to the more
rapid dispersal of toxic metabolic waste products.A series of experiments was undertaken to investigate the
possibility of maintaining juvenile flukes in vitro, from the
metacercarial stage. It was shown that the survival period could be
increased from two days, in a balanced salts solution, to 11 days by
the inclusion of more complex nutrients such as serum, blood or liver
extract in the medium. However, little or no growth occurred under
these conditions. Survival and growth were maximal when the young
flukes were able to feed on monolayers of living cells, but even
under the most favourable conditions growth was limited and compared
very unfavourably with that expected in vivo.In Section Two the continuous-flow culture apparatus was modified
to form a recirculating system, in which large groups of adult flukes
could be maintained for reasonably prolonged periods. Following
concentration, the medium in which flukes had thus been maintained
showed strong antigenic properties against sera from fluke-infected
animals. When flukes were maintained in Medium 199» it was shown
, that they continued to produce antigenic metabolites throughout a
nine day culture period, although the amounts produced decreased with
time.Subsequent studies indicated that the concentrated culture medium
contained a variety of antigenic components, including both heatstable
and heat-labile substances, which reacted to differing degrees
with serum from fluke-infected rabbits, sheep, rats and bovines.
These reactions were investigated using double diffusion immunoprecipitation
in agar and the Enzyme Linked Immunosorbent Assay
(ELISA), a serological technique which had not previously been applied
to fascioliasis. It was shown that metabolic antigen could be used
to follow the serological response developing in experimentally
infected animals, but there was no evidence to suggest that it
had any particular advantage over more readily obtainable somatic
fluke antigen. ELISA was found to be a useful technique, which
in some cases enabled the serological response to be detected at
an earlier stage than by immunodiffusion.In view of the apparently complex nature of the metabolic antigen,
it was concluded that in its present form it was not likely to be
suitable for application to the serodiagnosis of fascioliasis in the
field. However, since it is probably less complex than somatic
fluke antigen, it may provide a more suitable starting material from
which to attempt to isolate purified and species-specific antigens
for this purpose.In Section Three a series of experiments was undertaken to
establish whether laboratory animals immunised with metabolic antigens
derived from F, hepatica maintained in vitro would respond with the
production of antibodies and, if so, whether these were associated with
any degree of protection against a subsequent challenge infection.Rabbits immunised with metabolic antigen derived from adult flukes
produced antibodies, which showed certain features in common with those
present in the serum of rabbits carrying a patent fluke infection.
There was some evidence that these antibodies had an effect on the
course of the challenge infection, since the mean size of the flukes
recovered from the immunised animals was significantly smaller than
that of the flukes recovered from non-immunised control rabbits.
However, there was no significant difference between the two groups of
rabbits in terms of the numbers of flukes recovered. The host response
to the challenge infection, as indicated by the eosinophilia and
increase in plasma glutamate dehydrogenase, wan consistently less
in the immunised rabbits, but there were marked within-group
variations in these parameters and the differences between the two
groups were not of statistical significance,A series of experiments was then carried out, in which rats, of
a strain known to be capable of developing acquired resistance to
F. hepatica. were immunised with metabolic antigen prepared in various
ways from either adult or immature flukes. In all cases the immunised
animals produced antibodies to the immunising antigen, which again
showed some features in common with those present in the serum of
infected animals. However, it was also apparent that there were
significant differences between the antibody components of the two types
of sera. In particular, it was evident that the immunised rats were
not responding well to the non-protein component of the metabolic antigen,
in contrast to the infected animals, which showed a strong reaction with
this component of the antigen.There was no evidence that the antibodies resulting from "the
immunisation of rats with metabolic antigen of F. hepatica had any
effect on the course of a subsequent challenge infection. In no case
was there any significant difference between the immunised, and control
rats in terms of the numbers or sizes of flukes recovered from the
challenge infection, or the host response to challenge, as indicated
by the eosinophilia and plasma glutamate dehydrogenase assays.An attempt was made to verify the claim of Lang (1976) that mice
could be successfully proteoted against F, hepatica by immunisation
with the medium in which 16-day-old flukes had been incubated for
24- hours. The design of this experiment was similar, but not
identical, to that of Lang, but the results were in marked contrast,
there being no differences between the immunised and control mice
in terms of the infection rate, mortality rate or numbers of flukes
recovered from the challenge infection.It was therefore concluded that metabolic antigen derived from
adult or immature F. hepatica maintained in vitro as described was
incapable of stimulating resistance to a challenge infection, even
in a strain of animals known to be capable of demonstrating acquired
immunity to this parasite. This indicated that either the metabolic
antigens obtained in vitro were significantly different from those
produced in vivo, to the extent that they had lost the ability to
stimulate protective immunity in the host animal, or that there is
a need for some alternative or additional stimulus to the host
before such immunity can be initiated
A man's bones with 16th-century weapons and coins in a glacier near Zermatt, Switzerland
Late in the 16th century, a man fell into the glacier crossing a high Alpine pass between Switzerland and Italy. The ice has released him these last year
Isospin Breaking Corrections to the HVP with Domain Wall Fermions
We present results for the QED and strong isospin breaking corrections to the
hadronic vacuum polarization using Domain Wall fermions. QED is
included in an electro-quenched setup using two different methods, a stochastic
and a perturbative approach. Results and statistical errors from both methods
are directly compared with each other.Comment: 8 pages, 6 figures, presented at the 35th International Symposium on
Lattice Field Theory (Lattice 2017), Granada, Spain, June 18-24, 201
Special Issue: Modern Hardware
While database systems have long enjoyed a “free ride” with ever-increasing clock cycles of the CPU, in the last decade this increase stalled. On the computational side, we have seen an ever-increasing number of cores as well as the advent of specialized computing units ranging from GPUs via FPGA to chips with specific extensions. On the memory side, we not only observe a significant growth of the capacity of main memory, but a continued large performance impact of RAM latency on data access cost, recently aggravated by increasing NUMA effects. Storage-wise we have witnessed the introduction of NAND devices (e.g., SSDs) impacting the established role of magnetic disk drive. These advances taken together impact current database architectures and ask for adjustments, extensions or even a complete re-write in order to establish a scalable, affordable, and flexible foundation for data management systems of the future. This special issue focuses on conceptual and systems-architecture research related to the exploitation of modern hardware infrastructure for data management tasks. The five papers we finally selected for this special issue all went through a major revision in April–May 2015, and then a minor revision in July–August 2015, before being accepted in October–November 2015. We next present a brief summary of the accepted papers
A Farm Bill to Help Farmers Weather Climate Change
The Farm Bill has an enormous impact on climate change. Greenhouse gas emissions from agriculture account for almost 10 percent of total U.S. emissions and up to a quarter of all emissions globally. The Farm Bill encourages the use of carbon-intensive agricultural practices and products responsible for these emissions, but nonetheless offers several opportunities to quickly expand carbon sequestration, making it a critical piece of climate legislation. This essay will examine the climate impact of the Farm Bill, focusing on the commodity, conservation, and crop insurance programs. It then proposes politically feasible changes to these programs aimed at minimizing agricultural greenhouse gas emissions and maximizing carbon storage. The essay concludes with an ambitious, long-term set of Farm Bill proposals designed to transform the U.S. agricultural sector into a carbon sink
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