1,721,234 research outputs found
Molecular biological characterisation of amplified esterases from organophosphate resistant and susceptible 'Culex quinquefasciatus'.
Full text linkCulex mosquitoes, as well as being vectors of
filariasis
and
Japanese
encephalitis,
are a world wide biting nuisance. Organophosphorus insecticides
(OPs) have been
widely used to control Culex populations.
Resistance to
OPs
has
occurred
and
is
typically mediated by the increase in
non-specific
esterase
activity.
The two
esterases involved are classified as
'A'
and
'B'
esterases
with
respect to their
preference for the substrates α- or
β- naphthyl
acetate.
The
commonest
phenotype
involves two elevated esterases,
A2
and
B2,
which
occur
in
complete
linkage
disequilibrium. The over expression of esterase
B1 is due to
gene
amplification.
Initially, in order to further study the
molecular
biology
of
OP
resistance,
full
length cDNAs coding for both A2
and
B2
esterases
were
isolated
and
sequenced
from an OP resistant Sri Lankan strain
of
Culex
quinquefasciatus,
PelRR.
The B2 esterase cDNA was isolated with
PCR
using
primers
sharing
homology
with the B1 esterase cDNA and
has
97.4%
homology
with
esterase
B1
at the
amino acid level. This confirmed that the
B
esterases
belong to
an
allelic
series.
Partial genomic sequences of B2 esterase
from
PelRR
and
four
other
OP
resistant
Culex strains were identical. This suggests that the
initial B2
esterase amplification
has occurred only once. However, the
cDNA
sequence
of a
B1
esterase
cDNA
isolated from an OP resistant Cuban strain
of
Culex
quinquefasciatus,
MRES,
was
different to that of the previously published
B1
esterase
gene sequence.
At the
genomic level, the haplotype of the
Cuban
B1
esterase
gene,
based
on
EcoRI
endonuclease analysis, was also
different,
suggesting that the
initial
B1
esterase
gene amplification event has occurred at
least twice.
AB
esterase
cDNA
from
an OP susceptible strain, PelSS, has also
been
partially
sequenced.
PelSS
was
derived
from the same origins as PelRR but its
B
esterase
cDNA
sequence
and
haplotype
of the gene are different. Thus, the
B2
esterase
gene
conferring
OP
resistance,
as
well as being amplified, is only
found in the
resistant strain,
PelRR.
The A2 esterase cDNA was isolated by
screening a
PelRR
cDNA
expression
library with an anti-A2 antiserum.
The
cDNA coded
for
a protein
of
540
amino
acids (the same as B2 esterase) and
shared
47%
amino
acid
homology
with
B2
esterase. This strongly suggests that the two
genes
arose
from
a
duplication
of
an
ancestral counterpart. Furthermore, screening
of a
PelRR
genomic
library
with
A2 and B2 esterase gene probes suggests that the two
esterase
genes,
A2
and
B2
are situated in tandem within the
genome.
PCR was used to amplify the coding region
of the
PelRR
A2
esterase
cDNA
and
this was co-transfected into the
baculovirus
expression
system.
The
recombinant
virus expressed an active A esterase
Characterization of carboxylesterases involved in the insecticide resistance of Culex quinquefasciatus from the Caribbean and South America.
Full text linkThe organophosphate resistance-associated elevated
esterases
Estα2, Estβ1
and
Estβ2 were purified to homogeneity from larvae
of the
Cuban Habana
strain.
The
bimolecular rate constants (kas) of Habana Estβ1
with
a range
of organophosphates
were not significantly different to those of
PelRR Estβ21 ,
and were
higher
with
some organophosphates than PelRR Estα21 (Karunaratne
et al,
1993).
The
relative
insecticide binding efficiency of these esterases could
not, therefore,
explain why
co-amplified estα2 and estβ2 are out competing estβ1
in the
field.
On the
basis
of their
kas, both Habana Estα2 and Estβ2 could
be
distinguished from their
equivalents
purified from other strains.
In two organophosphate resistant strains
of
Culex
quinquefasciatus
from
Colombia
and Trinidad, possessing the amplified
esterase
genes estα3
and
estβl, the
EcoRI
restriction fragment lengths of the estβl genes
and their
flanking
regions
were
different both to each other and to those
previously reported
for
TEM-R
estβ11
(Raymond et aL, 1991) and MRES estβ12
(Vaughan
et aL,
1995).
There
were
a
number of significant differences between the
kas of
purified
Colombia,
Trinidad
and Habana Estβ1s. The low kas and high k3s for the
interaction
of
Colombia Estβ1
with several insecticides confirmed that, as
for
Estα21
and
Estβ21, the
main role
of
Estβ1 is sequestration. The kas of Habana, Colombia
and
Trinidad
Estβ1s
were
higher than that of the electrophoretically
identical
Est'β13
purified
from the
susceptible PelSS strain (Karunaratne et
al,
1995a). This
suggests that the
elevated
esterase-based mechanism confers resistance through
amplification
of
alleles
coding
C
for esterases having a higher reactivity with the
insecticides they
sequester
than esterases coded for by their non-amplified counterparts. A PelRR Estα21 antiserum had the same cross-reactivity
with
Habana
Estα2
as with
Estα21. However, both Habana Estβ1 and
Estβ2
had
a
cross-reactivity
of
approximately 150-fold less than the Estα2s
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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