7,217 research outputs found
Gravito-magnetic instabilities in anisotropically expanding fluids
Gravitational instabilities in a magnetized Friedman - Robertson - Walker
(FRW) Universe, in which the magnetic field was assumed to be too weak to
destroy the isotropy of the model, are known and have been studied in the past.
Accordingly, it became evident that the external magnetic field disfavors the
perturbations' growth, suppressing the corresponding rate by an amount
proportional to its strength. However, the spatial isotropy of the FRW Universe
is not compatible with the presence of large-scale magnetic fields. Therefore,
in this article we use the general-relativistic (GR) version of the
(linearized) perturbed magnetohydrodynamic equations with and without
resistivity, to discuss a generalized Jeans criterion and the potential
formation of density condensations within a class of homogeneous and
anisotropically expanding, self-gravitating, magnetized fluids in curved
space-time. We find that, for a wide variety of anisotropic cosmological
models, gravito-magnetic instabilities can lead to sub-horizonal, magnetized
condensations. In the non-resistive case, the power spectrum of the unstable
cosmological perturbations suggests that most of the power is concentrated on
large scales (small k), very close to the horizon. On the other hand, in a
resistive medium, the critical wave-numbers so obtained, exhibit a delicate
dependence on resistivity, resulting in the reduction of the corresponding
Jeans lengths to smaller scales (well bellow the horizon) than the
non-resistive ones, while increasing the range of cosmological models which
admit such an instability.Comment: 10 pages RevTex, 4 figures, accepted for publication in the
International Journal of Modern Physics
Screening for thoracoabdominal aortic aneurysms in patients with aortoiliac atherosclerosis: a preliminary study
Thoracoabdominal aortic aneurysms (TAAs) usually present with rupture and
carry a high morbidity and mortality rate. Early detection of TAAs with screening
methods and elective surgical repair could potentially diminish these complications.
The present study was aimed at screening for TAA in patients with
angiography-proven aortoiliac atherosclerosis (n = 43). A group of patients
without aortoiliac atherosclerosis was used as controls (n = 15). Age, sex and
aortic diameter at the level of the T12 vertebra were recorded. The subjects
were divided into two age categories, the first made up of those aged less
than 65 years and the second those aged 65 years or more. A T12 aortic
diameter greater than 35 mm was used to indicate TAA. Statistical analyses
were performed by independent t-test and general linear model with age
category, sex and atherosclerosis as factors. The mean T12 aortic diameters
were greater in patients with atherosclerosis than in the control group
(25.2 ± 5.0 vs. 22.9 ± 2.4 mm; p = 0.034). Two out of 43 patients (4.7%)
with aortoiliac atherosclerosis had TAA, while no one in the control group
had TAA. A general linear model showed that the interaction of age category
and sex significantly affected the T12 aortic diameter [F (1.49) = 4.044,
p = 0.050]. Post hoc (LSD) tests revealed that male patients aged over 65 had
greater T12 aortic diameters than other patients. We conclude that patients
with aortoiliac atherosclerosis may be at greater risk for developing TAA.
Ageing and male sex may also be associated with thoracoabdominal aortic
enlargement. (Folia Morphol 2008; 67: 78-83
Iliolumbar membrane, a newly recognised structure in the back
Despite intensive research in the anatomical sciences for the last two centuries,
some structures of the human body still remain controversial or incompletely
described.
We describe a new membranous fascial anatomical entity, which we refer to as
the iliolumbar membrane (ILM). During the 2004-2005 academic semesters at
the American University of the Caribbean School of Medicine we dissected
40 human cadavers fixed in formalin-alcohol-phenol solution. Iliolumbar membrane
is a thick connective tissue structure, deep to the skin, originating from
the fibres of the thoracolumbar fascia at the lateral border of the erector spinae.
It runs inferior to the superior border of the iliac crest, lateral to the posterior
superior iliac spine, overlying the iliac crest at the level of the 4th lumbar vertebra.
Iliolumbar membrane terminates within subcutaneous fat, where it divides
into multiple layers. All cadavers showed considerable variation in the blending
of the membrane’s multiple layers with the subcutaneous fat. However, all specimens
consistently showed a uniform appearance of ILM at the point of origin.
Iliolumbar membrane could be demonstrated objectively by ultrasound examination
with a frequency of 7.5 MHz and also with a Stryker endoscope. A hypothesis
is put forth, conjecturing that this new structure may have relevance in
creating a natural barrier between the musculature of the back and the muscles
of the gluteal region, similar to Scarpa’s fascia of the anterior abdominal wall
Suppression of inflammation and tissue damage by a hookworm recombinant protein in experimental colitis
Gastrointestinal parasites, hookworms in particular, have evolved to cause minimal harm to their hosts when present in small numbers, allowing them to establish chronic infections for decades. They do so by creating an immunoregulatory environment that promotes their own survival, but paradoxically also benefits the host by protecting against the onset of many inflammatory diseases. To harness the therapeutic value of hookworms without using live parasites, we have examined the protective properties of the recombinant protein anti-inflammatory protein (AIP)-1, secreted in abundance by hookworms within the intestinal mucosa, in experimental colitis. Colitic inflammation assessed by weight loss, colon atrophy, oedema, ulceration and necrosis, as well as abdominal adhesion was significantly suppressed in mice treated with a single intraperitoneal dose of AIP-1 at 1 mg kg(-1). Local infiltration of inflammatory cells was also significantly reduced, with minimal goblet cell loss and preserved mucosal architecture. Treatment with AIP-1 promoted the production of colon interleukin (IL)-10, transforming growth factor (TGF)-beta and thymic stromal lymphopoietin (TSLP), resulting in the suppression of tumour necrosis factor (TNF)-alpha, IL-13 and IL-17 A cytokines and granulocyte macrophage colony-stimulating factor (GM-CSF), CX motif chemokine ( CXCL)-11 and cyclooxygenase synthase (COX)-2 mRNA transcripts. AIP-1 promoted the accumulation of regulatory T cells in the colon likely allowing rapid healing of the colon mucosa. Hookworm recombinant AIP-1 is a novel therapeutic candidate for the treatment of inflammatory bowel diseases that can be explored for the prevention of acute inflammatory relapses, an important cause of colorectal cancer
Differences in transcription between free-living and CO_2-activated third-stage larvae of Haemonchus contortus
Background:
The disease caused by Haemonchus contortus, a blood-feeding nematode of small ruminants, is of major economic importance worldwide. The infective third-stage larva (L3) of this gastric nematode is enclosed in a cuticle (sheath) and, once ingested with herbage by the host, undergoes an exsheathment process that marks the transition from the free-living (L3) to the parasitic (xL3) stage. This study explored changes in gene transcription associated with this transition and predicted, based on comparative analysis, functional roles for key transcripts in the metabolic pathways linked to larval development.
Results:
Totals of 101,305 (L3) and 105,553 (xL3) expressed sequence tags (ESTs) were determined using 454 sequencing technology, and then assembled and annotated; the most abundant transcripts encoded transthyretin-like, calcium-binding EF-hand, NAD(P)-binding and nucleotide-binding proteins as well as homologues of Ancylostoma-secreted proteins (ASPs). Using an in silico-subtractive analysis, 560 and 685 sequences were shown to be uniquely represented in the L3 and xL3 stages, respectively; the transcripts encoded ribosomal proteins, collagens and elongation factors (in L3), and mainly peptidases and other enzymes of amino acid catabolism (in xL3). Caenorhabditis elegans orthologues of transcripts that were uniquely transcribed in each L3 and xL3 were predicted to interact with a total of 535 other genes, all of which were involved in embryonic development.
Conclusion:
The present study indicated that some key transcriptional alterations taking place during the transition from the L3 to the xL3 stage of H. contortus involve genes predicted to be linked to the development of neuronal tissue (L3 and xL3), formation of the cuticle (L3) and digestion of host haemoglobin (xL3). Future efforts using next-generation sequencing and bioinformatic technologies should provide the efficiency and depth of coverage required for the determination of the complete transcriptomes of different developmental stages and/or tissues of H. contortus as well as the genome of this important parasitic nematode. Such advances should lead to a significantly improved understanding of the molecular biology of H. contortus and, from an applied perspective, to novel methods of intervention
The clinical anatomy of the cephalic vein in the deltopectoral triangle
Identification and recognition of the cephalic vein in the deltopectoral triangle
is of critical importance when considering emergency catheterization procedures.
The aim of our study was to conduct a cadaveric study to access data
regarding the topography and the distribution patterns of the cephalic vein as
it relates to the deltopectoral triangle. One hundred formalin fixed cadavers
were examined. The cephalic vein was found in 95% (190 right and left) specimens,
while in the remaining 5% (10) the cephalic vein was absent. In 80%
(152) of cases the cephalic vein was found emerging superficially in the lateral
portion of the deltopectoral triangle. In 30% (52) of these 152 cases the cephalic
vein received one tributary within the deltopectoral triangle, while in 70%
(100) of the specimens it received two. In the remaining 20% (38) of cases the
cephalic vein was located deep to the deltopectoral fascia and fat and did not
emerge through the deltopectoral triangle but was identified medially to the
coracobrachialis and inferior to the medial border of the deltoid. In addition,
in 4 (0.2%) of the specimens the cephalic vein, after crossing the deltopectoral
triangle, ascended anterior and superior to the clavicle to drain into the subclavian
vein. In these specimens a collateral branch was observed to communicate
between the cephalic and external jugular veins. In 65.2% (124) of the cases
the cephalic vein traveled with the deltoid branch of the thoracoacromial trunk.
The length of the cephalic vein within the deltopectoral triangle ranged from
3.5 cm to 8.2 cm with a mean of 4.8 ± 0.7 cm. The morphometric analysis
revealed a mean cephalic vein diameter of 0.8 ± 0.1 cm with a range of 0.1 cm
to 1.2 cm. The cephalic vein is relatively large and constant, usually allowing
for easy cannulation. (Folia Morphol 2008; 67: 72-77
Identification of greater occipital nerve landmarks for the treatment of occipital neuralgia
Important structures involved in the pathogenesis of occipital headache include
the aponeurotic attachments of the trapezius and semispinalis capitis muscles
to the occipital bone. The greater occipital nerve (GON) can become entrapped
as it passes through these aponeuroses, causing symptoms of occipital neuralgia.
The aim of this study was to identify topographic landmarks for accurate
identification of GON, which might facilitate its anaesthetic blockade. The course
and distribution of GON and its relation to the aponeuroses of the trapezius and
semispinalis capitis were examined in 100 formalin-fixed adult cadavers. In addition,
the relative position of the nerve on a horizontal line between the external
occipital protuberance and the mastoid process, as well as between the mastoid
processes was measured. The greater occipital nerve was found bilaterally in all
specimens. It was located at a mean distance of 3.8 cm (range 1.5–7.5 cm)
lateral to a vertical line through the external occipital protuberance and the
spinous processes of the cervical vertebrae 2–7. It was also located approximately
41% of the distance along the intermastoid line (medial to a mastoid
process) and 22% of the distance between the external occipital protuberance
and the mastoid process. The location of GON for anaesthesia or any other
neurosurgical procedure has been established as one thumb’s breadth lateral to
the external occipital protuberance (2 cm laterally) and approximately at the
base of the thumb nail (2 cm inferior). This is the first study proposing the use of
landmarks in relation to anthropometric measurements. On the basis of these
observations we propose a target zone for local anaesthetic injection that is
based on easily identifiable landmarks and suggest that injection at this target
point could be of benefit in the relief of occipital neuralgia
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Diffusion tensor and volumetric magnetic resonance imaging using an MR-compatible hand-induced robotic device suggests training-induced neuroplasticity in patients with chronic stroke
Stroke is the third leading cause of mortality and a frequent cause of long-term adult impairment. Improved strategies to enhance motor function in individuals with chronic disability from stroke are thus required. Post-stroke therapy may improve rehabilitation and reduce long-term disability; however, objective methods for evaluating the specific impact of rehabilitation are rare. Brain imaging studies on patients with chronic stroke have shown evidence for reorganization of areas showing functional plasticity after a stroke. In this study, we hypothesized that brain mapping using a novel magnetic resonance (MR)-compatible hand device in conjunction with state-of-the-art magnetic resonance imaging (MRI) can serve as a novel biomarker for brain plasticity induced by rehabilitative motor training in patients with chronic stroke. This hypothesis is based on the premises that robotic devices, by stimulating brain plasticity, can assist in restoring movement compromised by stroke-induced pathological changes in the brain and that these changes can then be monitored by advanced MRI. We serially examined 15 healthy controls and 4 patients with chronic stroke. We employed a combination of diffusion tensor imaging (DTI) and volumetric MRI using a 3-tesla (3T) MRI system using a 12-channel Siemens Tim coil and a novel MR-compatible hand-induced robotic device. DTI data revealed that the number of fibers and the average tract length significantly increased after 8 weeks of hand training by 110% and 64%, respectively (p<0.001). New corticospinal tract (CST) fibers projecting progressively closer to the motor cortex appeared during training. Volumetric data analysis showed a statistically significant increase in the cortical thickness of the ventral postcentral gyrus areas of patients after training relative to pre-training cortical thickness (p<0.001). We suggest that rehabilitation is possible for a longer period of time after stroke than previously thought, showing that structural plasticity is possible even after 6 months due to retained neuroplasticity. Our study is an example of personalized medicine using advanced neuroimaging methods in conjunction with robotics in the molecular medicine era
Excretory/secretory products of the carcinogenic liver fluke are endocytosed by human cholangiocytes and drive cell proliferation and IL6 production
© 2015 Australian Society for Parasitology Inc. Liver fluke infection caused by Opisthorchis viverrini remains a major public health problem in many parts of Asia including Thailand, Lao PDR, Vietnam and Cambodia, where there is a strikingly high incidence of cholangiocarcinoma (CCA - hepatic cancer of the bile duct epithelium). Among other factors, uptake of O. viverrini excretory/secretory products (OvES) by biliary epithelial cells has been postulated to be responsible for chronic inflammation and proliferation of cholangiocytes, but the mechanisms by which cells internalise O. viverrini excretory/secretory products are still unknown. Herein we incubated normal human cholangiocytes (H69), human cholangiocarcinoma cells (KKU-100, KKU-M156) and human colon cancer (Caco-2) cells with O. viverrini excretory/secretory products and analysed the effects of different endocytic inhibitors to address the mechanism of cellular uptake of ES proteins. Opisthorchis viverrini excretory/secretory products was internalised preferentially by liver cell lines, and most efficiently/rapidly by H69 cells. There was no evidence for trafficking of ES proteins to cholangiocyte organelles, and most of the fluorescence was detected in the cytoplasm. Pretreatment with clathrin inhibitors significantly reduced the uptake of O. viverrini excretory/secretory products, particularly by H69 cells. Opisthorchis viverrini excretory/secretory products induced proliferation of liver cells (H69 and CCA lines) but not intestinal (Caco-2) cells, and proliferation was blocked using inhibitors of the classical endocytic pathways (clathrin and caveolae). Opisthorchis viverrini excretory/secretory products drove IL6 secretion by H69 cells but not Caco-2 cells, and cytokine secretion was significantly reduced by endocytosis inhibitors. This the first known study to address the endocytosis of helminth ES proteins by host epithelial cells and sheds light on the pathways by which this parasite causes one of the most devastating forms of cancer in south-eastern Asia
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