Molecular and antigenic characterization of bovine Coronavirus circulating in Argentinean cattle during 1994-2010

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Detection rate of BCoV was statistically higher in dairy than in beef calves.

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Argentinean strains are distant from the Mebus strain included in local vaccines.

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In vitro cross-protection between Arg95 field strain and Mebus reference strain.

Bovine coronavirus (BCoV) is an important viral pathogen associated with neonatal calf diarrhea. Our aim was to investigate the incidence of BCoV in diarrhea outbreaks in beef and dairy herds from Argentina during 1994–2010. A total of 5.365 fecal samples from diarrheic calves were screened for BCoV diagnosis by ELISA. The virus was detected in 1.71% (92/5365) of the samples corresponding to 5.95% (63/1058) of the diarrhea cases in 239 beef and 324 dairy farms. The detection rate of BCoV was significantly higher in dairy than in beef herds: 12.13% (29/239) vs. 4.32% (14/324) respectively. Phylogenetic analysis of the hypervariable S1 region of seven representative samples (from different husbandry systems, farm locations and years of sampling) indicated that BCoV strains circulating in Argentinean beef and dairy herds formed a cluster distinct from other geographical regions. Interestingly, Argentinean strains are distantly related (at both the nucleotide and amino acid levels) with the Mebus historic reference BCoV strain included in the vaccines currently available in Argentina. However, Mebus-induced antibodies were capable of neutralizing the BCoV Arg95, a field strain adapted to grow in vitro, and vice versa, indicating that both strains belong to the same CoV serotype reported in cattle. This work represents the first large survey describing BCoV circulation in Argentinean cattle.

Molecular epidemiology of avian infectious bronchitis in Brazil from 2007 to 2008 in breeders, broilers, and layers

Multiple lineages of Brazilian strains from 2007 to 2008 of avian infectious bronchitis virus (IBV) were detected in flocks of breeders, broilers, and layers. Organs samples from 20 IBV-positive flocks with variable clinical signs were submitted to the partial amplification of S gene (nucleotides 726-1071) of IBV. Fifteen of the 20 sequenced strains segregated in a unique Brazilian cluster subdivided in three subclusters (Brazil 01, 02, and 03). Whereas three strains could be classified as Massachusetts (Mass) genotype, the remaining two strains, originating from flocks with reproductive and respiratory disorders, grouped within the 4/91-793B genotype, a genotype that has not been detected before in Brazil. The potential relevance of the findings to the poultry industry is discussed because the low level of identity of the sequenced part of the S gene from 17 of 20 detected field strains and the vaccines of the Massachusetts serotype used suggest that the level of cross-protection by the Massachusetts vaccines might be low.

Charon's radius and atmospheric constraints from observations of a stellar occultation

The physical characteristics of Pluto and its moon, Charon, provide insight into the evolution of the outer Solar System. Although previous measurements have constrained the masses of these bodies, their radii and densities have remained uncertain. The observation of a stellar occultation by Charon in 1980 established a lower limit on its radius of 600 km (ref. 3) (later refined to 601.5 km; ref. 4) and suggested a possible atmosphere. Subsequent, mutual event modelling yielded a range of 600-650 km (ref. 5), corresponding to a density of 1.56 +/- 0.22 g cm(-3) (refs 2, 5). Here we report multiple-station observations of a stellar occultation by Charon. From these data, we find a mean radius of 606 +/- 8 km, a bulk density of 1.72 +/- 0.15 g cm(-3), and rock-mass fraction 0.63 +/- 0.05. We do not detect a significant atmosphere and place 3sigma upper limits on atmospheric number densities for candidate gases. These results seem to be consistent with collisional formation for the Pluto-Charon system in which the precursor objects may have been differentiated, and they leave open the possibility of atmospheric retention by the largest objects in the outer Solar System.

The recent expansion of Pluto's atmosphere

Stellar occultations--the passing of a relatively nearby body in front of a background star--can be used to probe the atmosphere of the closer body with a spatial resolution of a few kilometres (ref. 1). Such observations can yield the scale height, temperature profile, and other information about the structure of the occulting atmosphere. Occultation data acquired for Pluto's atmosphere in 1988 revealed a nearly isothermal atmosphere above a radius of approximately 1,215 km. Below this level, the data could be interpreted as indicating either an extinction layer or the onset of a large thermal gradient, calling into question the fundamental structure of this atmosphere. Another question is to what extent Pluto's atmosphere might be collapsing as it recedes from the Sun (passing perihelion in 1989 in its 248-year orbital period), owing to the extreme sensitivity of the equilibrium surface pressure to the surface temperature. Here we report observations at a variety of visible and infrared wavelengths of an occultation of a star by Pluto in August 2002. These data reveal evidence for extinction in Pluto's atmosphere and show that it has indeed changed, having expanded rather than collapsed, since 1988.

Hepatitis C virus genotypes in a northeastern area of Brazil

We used a reverse transcription-polymerase chain reaction (RT-PCR) to obtain the genotypes of circulating hepatitis C virus (HCV) in patients from a Gastro-Hepatology Unit in the city of Salvador (Bahia State) in northeastern Brazil. Viral RNA was detected in 83 (65.4%) of 127 anti-HCV seropositive serum samples. Positivity was significantly associated with alterations in levels of aspartate aminotransferase and alanine aminotransferase (P < 0.05). Genotyping of HCV was performed by RT-PCR using genotype-specific primers from the core region: 24.1% were infected with subtype 1a, 38.6% with 1b, 3.6% with 2, 21.7% with 3a, and 12.0% with a mixed genotype. There was no difference in genotype distribution when compared with results from other Brazilian locations. Surprisingly, the high frequency of genotype 3 in Brazilian samples continues to be different from that reported around the world and warrants further investigation.

Real-time position monitoring of invasive devices using magnetic resonance

Techniques which can be used to follow the position of invasive devices in real-time using magnetic resonance (MR) are described. Tracking of an invasive device is made possible by incorporating one or more small RF coils into the device. These coils detect MR signals from only those spins near the coil. Pulse sequences which employ nonselective RF pulses to excite all nuclear spins within the field-of-view are used. Readout magnetic field gradient pulses, typically applied along one of the primary axes of the imaging system, are then used to frequency encode the position of the receive coil(s). Data are Fourier transformed and one or more peaks located to determine the position of each receiver coil in the direction of the applied field gradient. Subsequent data collected on orthogonal axes permits the localization of the receiver coil in three dimensions. The process can be repeated rapidly and the position of each coil can be displayed in real-time.

MR-guided focused ultrasound surgery

Magnetic resonance guided focused ultrasound surgery provides a minimally invasive controlled method for selectively destroying deep-lying tissue. A thermal analysis of focused ultrasound provides an estimate of the time-dependent temperature distribution and thermal dose required for ultrasound surgery. The temperature distribution is estimated by accumulating heat sources, considering the effects of thermal conductivity, heat content, and perfusion. In this study, both gel phantoms and excised in vitro bovine muscle specimens were imaged in a 1.5 T MR system while heated with a 5 cm diameter, 10 cm focal length, 1.1 MHz transducer. During sonication, the thermal effects were observed with T1-weighted pulse sequences. Below a critical temperature, the heat zone appeared as a dark spot that moved with the focal spot. Above a critical thermal dose, the in vitro tissue was irreversibly altered and the focal lesion was observed on both the MR image and the specimen slice.

Secondary flow in the human common carotid artery imaged by MR angiography

The blood flow in arteries affects both the biology of the vessels and the development of atherosclerosis. The flow is three-dimensional, unsteady, and difficult to measure or to model computationally. We have used phase-shift-based magnetic resonance angiography to image and measure the flow in the common carotid arteries of a healthy human subject. There was curvature of the vessels and thin-slice dynamic flow imaging showed evidence of the presence of secondary motions. Flexing the cervical spine straightened the vessels and reduced the asymmetry of the flow.

Quantitative measurement of blood flow using cylindrically localized Fourier velocity encoding

A procedure for the quantitative measurement of blood velocity was developed and evaluated in the portal vein, aorta, and vena cava of healthy volunteers. This procedure utilizes Fourier velocity encoding and can be performed with or without cardiac gating. The accuracy of velocity measurements is determined by the accuracy of the gradient subsystem. Flow measurements derived from the velocity measurement are further limited in their accuracy by the luminal cross-section measurement. Spatial localization is accomplished with an excitation pulse having a cylindrical rather than slab geometry. Data are acquired in the presence of a readout gradient to provide resolution along the cylindrical axis.

Simultaneous acquisition of phase-contrast angiograms and stationary-tissue images with Hadamard encoding of flow-induced phase shifts

A technique for the simultaneous acquisition of three-dimensional phase-contrast angiograms and stationary-tissue images is described. Hadamard multiplexed encoding of flow information permits image acquisition times that are a third shorter than those of previous phase-contrast methods. The encoding scheme described also enables differentiation of flow-induced phase shifts from phase shifts due to resonance offset conditions such as field inhomogeneities and chemical shift. Display strategies that combine this phase information with the flow image are described.

A method of coronary MR angiography

Procedures for the in vivo detection of coronary (and pulmonary) vessels using MR angiographic techniques were investigated. The most successful technique used gradient-recalled thin slice acquisitions that were gated to the cardiac cycle. The resulting data sets consist of three spatial dimensions and one time dimension. Acquisition of four dimensions of data proved necessary to obtain useful images of small vessels located on the moving myocardium.

Clinical evaluation of stenosis of the carotid bifurcation with magnetic resonance angiographic techniques

We evaluated the images of 60 carotid artery bifurcations in 31 patients suspected to have carotid artery disease who underwent invasive carotid angiography and combined two-dimensional, phase-sensitive and a gradient-echo magnetic resonance angiography. The phase scans consisted of seven serial projections that were obtained at 20 degrees intervals (11.0 minutes) around the carotid bifurcation; the gradient-echo (GRASS) scans were composed of 11 axial images (2.4 minutes) acquired through the bifurcation. The two magnetic resonance angiographic techniques yielded complementary pieces of information and were used together to compare magnetic resonance angiography with invasive angiography. Comparison of magnetic resonance and invasive angiograms of the 60 carotid arteries shows that the sensitivity (86%) and specificity (92%) of the magnetic resonance angiographic techniques we used to diagnose clinically significant carotid stenosis approach but do not reach those of invasive angiography.

Volume rendering and connectivity algorithms for MR angiography

Several display algorithms for three-dimensional angiographic data are evaluated. The mathematical analysis assumes additive Gaussian noise to predict the background distribution function for maximum intensity projection, sum projection, and connectivity display methods. In the maximum intensity projection method the mean noise level increases with the number of voxels in the ray, while in the sum projection the noise distribution width increases with the projection thickness, but the mean level remains constant. Comparisons of maximum intensity projection, sum projection, and connectivity algorithms applied to an MR angiogram of the circle of Willis are made. Measurements of the noise distribution are in agreement with the analysis. Algorithms combining connectivity with maximum intensity and sum projection are also evaluated. In these methods, a projection image is created using only the voxels marked by connectivity, typically with a 6% threshold of the data. Fine vessels are resolved and background noise is reduced in agreement with the analysis.

In vivo non-invasive studies on the human lens

Progress in biophysical technology now permits us to monitor aging and precataractous changes in the human ocular lens in vivo as well as in vitro. We are employing two noninvasive techniques to measure changes in lens fluorescence and in one lens water compartment (T2) utilizing Scheimpflug lens fluorescence densitography and magnetic resonance imaging. These studies demonstrate age-related changes in the normal lens as reflected by enhanced fluorescence and longer T2 values. Precataractous changes can also be detected with this approach.

Magnetic resonance angiography of abdominal vessels: early experience using the three-dimensional phase-contrast technique

Based on three-dimensional acquisition of three sequences sensitive to one flow-direction, abdominal magnetic resonance phase-contrast angiography (MRA) was performed in 13 volunteers and 20 patients. The subjects received no antiperistaltic medication and were allowed to breath normally during the three acquisition periods of 11 minutes. The frequency of demonstration of the normal aorta, superior mesenteric and right and left renal arteries was 100%/100%/91%/100%, and of the inferior vena cava, splenic, superior mesenteric and portal veins was 92%/67%/92%/100%, respectively, whereas other abdominal vessels were seen less constantly. In renal artery stenosis or occlusion, MRA detected eight out of nine pathological arteries, missed only a minimal stenosis and was never false positive. In all 10 cases of portal hypertension, MRA demonstrated the venous collaterals detected by conventional angiography and in six cases showed more collaterals, particularly paravertebral vessels. A Budd-Chiari syndrome was investigated as well. If the accuracy of MRA can be proved in larger studies, it may become an important diagnostic tool in evaluating abdominal vascular pathology, such as renal artery stenosis or portal hypertension.

Evaluation of the carotid artery bifurcation: comparison of magnetic resonance angiography and digital subtraction arch aortography

Thirty-four carotid artery bifurcations were examined using both magnetic resonance angiography (MRA) and digital subtraction arch aortography to determine their accuracy when compared to selective carotid angiography. The sensitivity of MRA was 73% and its specificity was 91% when compared with selective carotid angiography. The sensitivity of arch aortography was 27% and its specificity was 100%.

The NMR phased array

We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm).

Three-dimensional phase-contrast MR angiography in the head and neck: preliminary report

Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnormalities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angiograms in 37 min and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of arteriovenous malformations were well delineated; aneurysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities.

Peripheral vascular and abdominal applications of MR flow imaging techniques

Many MR flow imaging techniques that have been successfully applied in the carotid arteries and intracranial circulation have been tested in the peripheral and abdominal vasculature. The results have been variable. The lack of success can be attributed to different imaging requirements as well as different patterns of blood flow. These requirements include a large field of view, sensitivity to a wide range of blood flow velocities and complex flow directions, and suppression of overlapping vascular structures and stationary tissue. We have designed strategies using phase contrast MR angiography (MRA) for imaging the arteries and veins of the lower extremity and the abdominal vasculature in normal subjects. This strategy takes advantage of the pulsatile flow pattern present in normal arteries. Overlapping blood flow and stationary tissue were suppressed by a combination of spatial presaturation, optimization of the amplitude and duration of the velocity sensitive gradients, and postprocessing techniques.

Three-dimensional phase-contrast MR angiography in the head and neck: preliminary report

Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnormalities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angiograms in 37 min and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of arteriovenous malformations were well delineated; aneurysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities.

MR angiography with two-dimensional acquisition and three-dimensional display. Work in progress

Magnetic resonance arteriograms of healthy volunteers and selected patients were produced with a new spoiled gradient-echo pulse sequence based on time-of-flight phenomena. The procedure involves sequential acquisition of many contiguous, thin (1.5-mm) axial two-dimensional sections. These volume data are then submitted to a raytracing projection program, which retrospectively yields multiple arbitrary projection angles rotating through any plane. Venous structures are suppressed with a presaturation slab superior to the current section. The slab location is advanced in concert with advancement of each new section location. The acquisition time varies from 6 to 13 minutes, depending on the number of sections acquired for three-dimensional display. This method obviates the subtraction of image data sets to suppress signals from stationary spins, is more sensitive to slow blood flow than three-dimensional methods of acquisition, and shows special promise for the study of extracranial vascular disease.

Three-dimensional time-of-flight magnetic resonance angiography using spin saturation

A three-dimensional Fourier transform magnetic resonance imaging technique is presented. This procedure can be used to selectively detect flowing material such as blood in arteries and veins. Since flow is detected in a manner in which velocity-induced phase shifts are compensated, signal loss arising from complex flow and turbulence is minimized. The flow image is sensitive to all velocity components of flow. Applications of this technique are limited, however, to relatively straight vessels having appreciable flow. Examples of application of this technique to healthy and diseased carotid arteries are shown.

3DFT MR angiography of carotid and basilar arteries

Three-dimensional Fourier transform (3DFT) time-of-flight and two-dimensional Fourier transform (2DFT) projection phase-contrast MR angiography was performed in eight healthy volunteers and in 14 patients with known carotid artery or basilar artery occlusion, stenosis, or dissection. Comparative angiography was available in 13 cases (although in some cases the studies were separated by a number of months) and duplex sonography in one case. After localization of the carotid artery bifurcations by using 2DFT projection phase-contrast angiography, multiple 1.25-mm contiguous images were obtained with the 3DFT technique. In all cases, the lesions were identified on MR angiography. Because flow is detected in a manner that is independent of flow-induced phase shifts in the 3DFT time-of-flight technique, signal loss arising from complex flow and turbulence is minimized, yet the flow image remains sensitive to all velocity components of flow. Applications of this technique are ideal for relatively straight vessels where flow is laminar, but it can also be used to evaluate the carotid artery bifurcations where flow becomes complex.

Three-dimensional phase contrast angiography

Bipolar flow-encoding gradients can be used in a three-dimensional magnetic resonance imaging procedure to provide a noninvasive measure of in vivo blood flow. The resulting volume angiogram is a three-dimensional data matrix which can be retrospectively analyzed and displayed in a variety of ways. This angiographic technique provides good suppression of signals arising from stationary tissue, thereby permitting the visualization of small vessels having relatively slow flow. This suppression is obtained by modulating the amplitude of the flow-encoding gradient pulse to either cancel the stationary tissue signal or displace it relative to the flow signal in the volume image.

SIMA: simultaneous multislice acquisition of MR images by Hadamard-encoded excitation

We present a method of multislice magnetic resonance imaging that utilizes simultaneous binary-encoded excitation. Signals are acquired from all slices at once, and the images are separated in the reconstruction process. This simultaneous multislice acquisition method has been implemented for multislice spin-echo imaging, and the results are compared with those for a standard interleaved multislice method. Advantages include improved signal-to-noise ratios and flexible slice placement. Phantom and volunteer studies are presented and evaluated in comparison with competing methods.

Quantitative flow measurement in phase contrast MR angiography

The quantitative nature of phase contrast magnetic resonance angiography is explored, and a technique of blood flow measurement that is independent of system and patient parameters is presented. Phantom and patient studies demonstrate that quantitative flow measurements by phase contrast angiography can be routinely obtained with good accuracy despite nonuniform sensitivity profiles, blood flow pulsatility, and patient-to-patient changes in system gain. The calibration method requires the acquisition of only two flow images and thus can be performed as part of an angiographic session. Flow calibration of any flow profile can be accomplished with this technique. The solutions for plug flow and parabolic flow are presented.

Time-resolved magnetic resonance angiography

A time-resolved phase contrast magnetic resonance angiography technique is described. This technique provides a series of angiograms obtained at different phases of the cardiac cycle. Such a series of angiograms can be used to evaluate blood flow dynamics. For example, turbulent flow in the regions of vessel bifurcations is easily demonstrated and followed during systole and diastole. Retrograde flow can also be observed. Dynamic angiography can be particularly useful in distinguishing transient image features, such as signal voids due to turbulent flow, from static features arising from vessel morphology.

Rapid scan magnetic resonance angiography

The change in phase of transverse spin magnetization induced by macroscopic spin motion in the direction of an applied magnetic field gradient is used to generate projection angiograms. The method can provide a quantitative measure of laminar and pulsatile flow. Cardiac synchronization is not required provided that data are acquired at many points in the cardiac cycle. The use of short TR and a large number of excitations provides better suppression of stationary tissue and patient motion artifacts than is possible with cardiac gated studies. In addition to improvements in image quality, a substantial shortening of scan time is obtained.

Multiecho magnetic resonance angiography

Several pulse sequences which generate projected MR angiograms are presented. These pulse sequences exploit multiple-gradient refocused echoes to obtain several independent angiograms, which can be combined or separately analyzed to provide more information than an individual angiogram. For example, a series of angiograms, each with a different projection axis, can be obtained in the time required to obtain a single angiogram using a single-echo method. If the view angle of each echo is the same, then the acquired angiograms can be added to enhance the signal-to-noise ratio. Another pulse sequence simultaneously obtains two or more angiograms, sensitive to orthogonal flow components of the overall blood flow. These angiograms are then added to give an angiogram which is sensitive to flow in all directions.

Lead and cadmium concentrations in the hair of fishermen from the Subae River basin, Brazil

Previous studies have shown heavy pollution by lead and cadmium in the Subae River basin, State of Bahia, Brazil, caused by a lead smelter. Concentrations of these metals were determined in scalp hair of fishermen from three riverside towns and from a reference town. Increased levels for both metals were associated with increasing proximity to the smelter. Mean concentrations of lead and cadmium were higher among fishermen with straight hair than among those with curly hair. The effects of hair washing, hair type, and color and age on metal concentrations in fishermen's hair were studied.