9,326 research outputs found
Utility of polymerase chain reaction using two probes for rapid diagnosis of tubercular pleuritis in comparison to conventional methods
We have used polymerase chain reaction (PCR) with IS6110 and a new set of primers from an insertion element
like repetitive sequence, (TRC4) to detect Mycobacterium tuberculosis in pleural effusion samples from 50
patients having pleuritis. The results of PCR were compared with the results of conventional methods like
smear, culture and adenosine deaminase activity. Thirty six specimens were positive and 14 were negative by
PCR. Among the 36 samples, 33 were from patients with clinical evidence of tuberculosis including response to
anti-tuberculosis therapy. Only six samples were positive by the gold standard which is culture, and three were
positive by smear. The measurement of adenosine deaminase activity classified 19 samples as positives. The
overall sensitivity and specificity of PCR was 100 and 85 per cent respectively. PCR using IS6110 and TRC4
primers is a sensitive test as compared to conventional tests for detection of M. tuberculosis from pleural fluid
samples of patients with tubercular pleuritis
The fate of Mycobacterium tuberculosis in activated human macrophages
Human peripheral blood monocytes, that are unstimulated
in vitro, permit free multiplication of
intracellular Mycobacterium tuberculosis after 72 h in
culture. There was no killing of bacilli in the intracellular
environment even after in vitro activation of
monocytes with a cocktail of lipopolysaccharide,
phorbol myristate acetate, interferon gamma and
tumour necrosis factor-alpha. We also tested the
ability of adenosine triphosphate (ATP) in reducing
the intracellular viability of mycobacteria. Infected
monocytes upon ATP treatment underwent cell death,
but no loss in the intracellular viability of M. tuberculosis
or M. smegmatis could be observed
Isolation and characterization of an insertion element-like repetitive sequence specific for Mycobacterium tuberculosis complex
We report the characterization of an insertion-like
repetitive sequence containing the clone of Mycobacterium
tuberculosis. This repetitive sequence contains
seven inverted repeats. Restriction fragment length
polymorphism studies using this probe have shown
that it is not a highly polymorphic probe but rather
shows conservative fingerprint pattern. Out of the 150
strains tested, only three showed different fingerprint
patterns. It has several direct and inverted repeats.
Homology studies of the putative protein coding region
show that this repeat element might code for a
metalloproteinase of M. tuberculosis. Homology studies
also implicate this repeat element to be from a very
essential region of the M. tuberculosis genome participating
in recombination. This repeat has been found
to be an ideal target for polymerase chain reaction to
detect M. tuberculosis
Ginsparg-Wilson Fermions: A study in the Schwinger Model
Qualitative features of Ginsparg-Wilson fermions, as formulated by Neuberger,
coupled to two dimensional U(1) gauge theory are studied. The role of the
Wilson mass parameter in changing the number of massless flavors in the theory
and its connection with the index of the Dirac operator is studied. Although
the index of the Dirac operator is not related to the geometric definition of
the topological charge for strong couplings, the two start to agree as soon as
one goes to moderately weak couplings. This produces the desired singularity in
the quenched chiral condensate which appears to be very difficult to reproduce
with staggered fermions. The fermion determinant removes the singularity and
reproduces the known chiral condensate and the meson mass within understandable
errors.Comment: Corrected a few typos and changed some references. Minor changes to
the conten
Fermion-scalar interactions with domain wall fermions
Domain wall fermions are defined on a lattice with an extra direction the
size of which controls the chiral properties of the theory. When gauge fields
are coupled to domain wall fermions the extra direction is treated as an
internal flavor space. Here it is found that this is not the case for scalar
fields. Instead, the interaction takes place only along the link that connects
the boundaries of the extra direction. This reveals a richness in the way
different spin particles are coupled to domain wall fermions. As an
application, 4-Fermi models are studied using large N techniques and the
results are supported by numerical simulations with N=2. It is found that the
chiral properties of domain wall fermions in these models are good across a
large range of couplings and that a phase with parity-flavor broken symmetry
can develop for negative bare masses if the number of sites along the extra
direction is finite.Comment: LaTeX, 17 pages, 8 eps figures; comment regarding the width of Aoki
phase added in sec. 3; references adde
Development of DNA probes for M. tuberculosis
Attempts were made to develop DNA
probes for M. tuberculosis. Random library of M.
tuberculosis was constructed in plasmid pGEM -4.
Selection of recombinant clones was made by hybridisation
with 32P labelled M. tuberculosis probe.
Ten recombinant clones were selected on the basis
of strong signals from the random library.
These 10 clones named pTRC1-10 were subjected to
tests for specificity and sensitivity. On this basis,
pTRC4 was chosen and this is also, useful in restriction
fragment length polymorphism (RFLP)
studies
Domain Wall Fermions in Quenched Lattice QCD
We study the chiral properties and the validity of perturbation theory for
domain wall fermions in quenched lattice QCD at beta=6.0. The explicit chiral
symmetry breaking term in the axial Ward-Takahashi identity is found to be very
small already at Ns=10, where Ns is the size of the fifth dimension, and its
behavior seems consistent with an exponential decay in Ns within the limited
range of Ns we explore. From the fact that the critical quark mass, at which
the pion mass vanishes as in the case of the ordinary Wilson-type fermion,
exists at finite Ns, we point out that this may be a signal of the parity
broken phase and investigate the possible existence of such a phase in this
model at finite Ns. The rho and pi meson decay constants obtained from the
four-dimensional local currents with the one-loop renormalization factor show a
good agreement with those obtained from the conserved currents
On the continuum limit of fermionic topological charge in lattice gauge theory
It is proved that the fermionic topological charge of SU(N) lattice gauge
fields on the 4-torus, given in terms of a spectral flow of the Hermitian
Wilson--Dirac operator, or equivalently, as the index of the Overlap Dirac
operator, reduces to the continuum topological charge in the classical
continuum limit when the parameter is in the physical region .Comment: latex, 18 pages. v2: Several comments added. To appear in J.Math.Phy
Domain-wall fermions with dynamical gauge fields
We have carried out a numerical simulation of a domain-wall model in
-dimensions, in the presence of a dynamical gauge field only in an extra
dimension, corresponding to the weak coupling limit of a ( 2-dimensional )
physical gauge coupling. Using a quenched approximation we have investigated
this model at 0.5 ( ``symmetric'' phase),
1.0, and 5.0 (``broken'' phase), where is the gauge coupling constant of
the extra dimension. We have found that there exists a critical value of a
domain-wall mass which separates a region with a fermionic zero
mode on the domain-wall from the one without it, in both symmetric and broken
phases. This result suggests that the domain-wall method may work for the
construction of lattice chiral gauge theories.Comment: 27 pages (11 figures), latex (epsf style-file needed
Identification of the promoter of amidase gene for expression of useful mycobacterial genes
The genetics of mycobacteria has lagged behind because of several reasons.
Mycobacteria grow very slowly. their generation time ranging anywhere between 12-24
hrs. Mycobacteria are rather hydrophobic and tend to grow in clusters and there is
difficulty in purifying individual cells for genetic analysis. Very few genetic markers have
been found in mycobacteria because there is no known naturally occurring genetic
exchange in mycobacteria. With the creation of genomic libraries of M. tuberculosis more
than 50 genes have been characterised. Many of them are not expressed efficiently in
Escherichia coli (E.coli) under the control of their own promoters, since very few
mycobacterial promoters are recognised by the E. coli transcription machinery. This clearly
shows that mycobacteria use a different system of gene regulation. Understanding the gene
regulation of mycobacteria might throw light on the slow growth rate, about their
persistence in a resting phase and also about their intracellular survival. Besides this if
inducible or strong promoters are identified they can be used in over expression of genes
coding for proteins useful in diagnosis and protection
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